Cruise Report for the 2021 Reoccupation of A22
**********************************************


GO-SHIP A22 2021 Hydrographic Program
=====================================


Cruise Scientific Objectives
----------------------------

Viviane Menezes

The A22 2021 cruise aboard the UNOLS vessel R/V Thomas G. Thompson was
undertaken as part of the US GO-SHIP (Global Ocean Ship-based
Hydrographic Investigations Program), a major contributor to
international GO-SHIP. The program’s overall objective is to collect
quasi-decadal, highly accurate, surface-to-bottom, coast-to-coast,
physical, and chemical oceanic observations. These measurements are
essential to monitoring long-term changes in heat, freshwater, carbon,
oxygen, and other tracers in the global ocean– the main reservoir in
the Earth System.

The A22 meridional transect spans the western North Atlantic from the
tropics to the subtropics and is the only GO-SHIP transect in the
Caribbean Sea. This year, the A22 worked from South America’s
continental shelf break, near Aruba, to Puerto Rico and thence
northwards to Bermuda along the 66o W meridian. From Bermuda, the
transect stretched to the continental shelf south of Woods Hole,
following the Line W path (scienceweb.whoi.edu/linew/index.php). This
is the first reoccupation of Line W after the end of that program in
2014, whose objective was monitoring the deep limb of the Atlantic
Meridional Overturning Circulation (AMOC).

Along the way, the A22 transect crossed major western boundary
currents systems: the Caribbean Current, the Gulf Stream, and the
North Atlantic Deep Western Boundary Current (DWBC) at different
latitudes. The latter two are primary conduits of the AMOC.

Although the A22 transect has been slightly modified over the years,
this was the fourth reoccupation of this line in the last three
decades. The A22 was first occupied in 1997 (79 stations; R/V Knorr)
during WOCE (World Ocean Circulation Experiment), then in 2003 (82
stations; R/V Knorr) and 2012 (81 stations; R/V Atlantis) as part of
the CLIVAR (Climate Variability and Predictability).

In 2021, 90 CTD/LADCP/rosette stations were performed over the course
of 27-days during boreal spring (20 April - 16 May 2021). Stations
were nominally spaced by about 30 nm (50 km) in the open-ocean but
closer (<= 15 nm) at boundary currents and major topographic features.
At each station, a suite of surface to bottom vertical profiles was
collected using electronic sensors (CTDO, LADCPS, chi-pods,
transmissometer, UVP (Underwater Vision Profile)), and 36 Niskin
bottles for sampling water at discrete vertical levels.

Data collected during the A22 2021 were (some samplings will be
processed in labs onshore):

* Pressure, temperature, salinity, dissolved oxygen

* Fluorescence, shear and micro-scale temperature

* Current velocities from lowered and shipboard ADCPs

* Major nutrients (silicate, phosphate, nitrate, nitrite)

* Transient tracers (Chlorofluorocarbons (CFC-11 and 12), Sulphur
  Hexafluoride (SF_6) and Nitrous Oxide (N_2O))

* Carbon components: total dissolved inorganic carbon (DIC), total
  alkalinity, pH, and partial pressure of CO_2, dissolved organic
  carbon (DOC), total dissolved nitrogen (TDN)

* Nitrate isotopes and radiocarbons

* HPLC pigments and particulate organic carbon (POC)

* Sargassum seaweed

* Bathymetry and shipboard meteorological observations

* UVP high-resolution digital images to study large (>100 µm)
  particles and zooplankton

* Size-fractioned microbial respiration

* \delta^18O (ratio of stable isotopes oxygen-18 and oxygen-16) and
  \deltaD (Deuterium) for studying the hydrological cycle

In addition to the above measurements, during the A22 8 Argo (Core), 4
Go-BGC and 2 RAFOS floats, and 19 solar-powered spotter buoys
(measuring wave, wind, and sea surface temperature) were deployed.


Programs and Principal Investigators
------------------------------------

+---------------------------+---------------------------+---------------------------+---------------------------+
| Program                   | Affiliation               | Principal Investigator    | Email                     |
|===========================|===========================|===========================|===========================|
| *CTDO* Data, Salinity,    | *UCSD*, *SIO*             | Susan Becker, Jim Swift   | sbecker@ucsd.edu,         |
| Nutrients, Dissolved O_2  |                           |                           | jswift@ucsd.edu           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Total CO_2 (DIC)          | *AOML*, *PMEL*, *NOAA*    | Richard Feely, Rik        | richard.a.feely@noaa.gov, |
|                           |                           | Wanninkhof                | Rik.Wanninkhof@noaa.gov   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Underway Temperature,     | *PMEL*, *NOAA*            | Simone Alin               | simone.r.alin@noaa.gov    |
| Salinity, and pCO_2       |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Total Alkalinity, pH      | *SIO*, *RSMAS*            | Andrew Dickson, Frank     | adickson@ucsd.edu,        |
|                           |                           | Millero                   | fmillero@rsmas.miami.edu  |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Discrete pCO_2            | *PMEL*, *NOAA*            | Rik Wanninkhof            | Rik.Wanninkhof@noaa.gov   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| SADCP                     | *UH*                      | Eric Firing               | efiring@soest.hawaii.edu  |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *LADCP*                   | *LDEO*                    | Andreas Thurnherr         | ant@ldeo.columbia.edu     |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *CFCs*, *SF6*, *N2O*      | *UW*                      | Mark Warner               | warner@u.washington.edu   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *DOC*, *TDN*              | *UCSB*                    | Craig Carlson             | craig_carlson@ucsb.edu    |
+---------------------------+---------------------------+---------------------------+---------------------------+
| C13 & C14                 | *UW*, *WHOI*              | Rolf Sonnerup, Roberta    | rolf@uw.edu,              |
|                           |                           | Hansman                   | rhansman@whoi.edu         |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Transmissometry           | *TAMU*                    | Wilf Gardner              | wgardner@ocean.tamu.edu   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Chipod                    | *OSU*                     | Jonathan Nash             | nash@coas.oregonstate.edu |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Argo Floats               | *WHOI*                    | Susan Wijffels, Steven    | swijffels@whoi.edu,       |
|                           |                           | Jayne, Pelle Robbins      | sjayne@whoi.edu,          |
|                           |                           |                           | probbins@whoi.edu.        |
+---------------------------+---------------------------+---------------------------+---------------------------+
| BGC Floats                | *MBARI*, *UW*,            | Kenneth Johnson, Steven   | johnson@mbari.org,        |
|                           | *Princeton*, *SIO*,       | Riser, Jorge Sarmiento,   | riser@uw.edu,             |
|                           | *WHOI*                    | Lynne Talley, Susan       | jls@princeton.edu,        |
|                           |                           | Wijffels                  | ltalley@ucsd.edu,         |
|                           |                           |                           | swijffels@whoi.edu        |
+---------------------------+---------------------------+---------------------------+---------------------------+
| RAFOS Floats              | *WHOI*                    | Viviane Menezes           | vmenezes@whoi.edu         |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Canadian Arvor Floats     | *DFO-MPO*                 | Clark Richards            | Clark.Richards@dfo-       |
|                           |                           |                           | mpo.gc.ca                 |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Nitrate isotopes          | *Princeton*               | Daniel Sigman             | sigman@princeton.edu      |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Oxygen isotopes           | *UArizona*                | Kaustubh Thirumalai       | kaustubh@email.arizona.e  |
|                           |                           |                           | du                        |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *UVP*                     | *UAF*                     | Andrew McDonnell          | amcdonnell@alaska.edu     |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Spotter drifters          | Sofar Ocean               | Cameron Dunning           | cameron@sofarocean.com    |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Sargassum                 | *WHOI*                    | Dennis McGillicuddy       | dmcgillicuddy@whoi.edu    |
+---------------------------+---------------------------+---------------------------+---------------------------+


Science Team and Responsibilities
---------------------------------

+---------------------------+---------------------------+---------------------------+---------------------------+
| Duty                      | Name                      | Affiliation               | Email Address             |
|===========================|===========================|===========================|===========================|
| Chief Scientist           | Viviane Menezes           | *WHOI*                    | vmenezes@whoi.edu         |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Co-Chief Scientist        | Jesse Anderson            | *WHOI*                    | jessea785@gmail.com       |
+---------------------------+---------------------------+---------------------------+---------------------------+
| CTD Watchstander          | Holly Olivarez            | *CU Boulder*              | holly.olivarez@colorado.  |
|                           |                           |                           | edu                       |
+---------------------------+---------------------------+---------------------------+---------------------------+
| CTD Watchstander          | Maya Prabhakar            | *UArizona*                | mayaprabhakar@email.ariz  |
|                           |                           |                           | ona.edu                   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| CTD Watchstander          | Victoria Schoenwald       | *U Miami*                 | vks16@rsmas.miami.edu     |
+---------------------------+---------------------------+---------------------------+---------------------------+
| LADCP, CTD Watchstander   | Ali Siddiqui              | *JHU*                     | asiddi24@jhu.edu          |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Nutrients, *ODF*          | Susan Becker              | *UCSD* *ODF*              | sbecker@ucsd.edu          |
| supervisor, *SOCCOM*      |                           |                           |                           |
| floats                    |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Nutrients                 | Alexandra Fine            | *NOAA*                    | alexandra.fine@noaa.gov   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| CTDO Processing           | Michael Kovatch           | *UCSD* *ODF*              | mkovatch@ucsd.edu         |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Salts, ET, CTD/Rosette    | John Calderwood           | *UCSD* *SEG*              | jcalderwood@ucsd.edu      |
| Maintenance               |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Salts, CTD/Rosette        | Caitlyn Webster           | *UCSD* *STS*              | cwebster@ucsd.edu         |
| Maintenance               |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Dissolved O_2, Database   | Andrew Barna              | *UCSD* *ODF*              | abarna@ucsd.edu           |
| Management                |                           |                           |                           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Dissolved O_2             | Robert Freiberger         | *UCSD*                    | rfreiberger@ucsd.edu      |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *UVP*                     | Stephane O’Daly           | *UAF*                     | shodaly2@alaska.edu       |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *DIC*, underway pCO2      | Andrew Collins            | *UW*                      | andrew.collins@noaa.gov   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| pCO2                      | Patrick Mears             | *U Miami*                 | patrick.mears@noaa.gov    |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *DIC*                     | Charles Featherstone      | *NOAA*                    | charles.featherstone@noa  |
|                           |                           |                           | a.gov                     |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *CFCs*, SF6               | Mark Warner               | *UW*                      | warner@u.washington.edu   |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *CFCs*, SF6               | Bonnie Chang              | *UW*                      | bxc@uw.edu                |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *CFCs*, SF6 student       | Lillian Henderson         | *U Miami*                 | lch39@miami.edu           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| pH, Total Alkalinity      | Sidney Wayne              | *HPU*                     | sidneyelisawayne@gmail.c  |
|                           |                           |                           | om                        |
+---------------------------+---------------------------+---------------------------+---------------------------+
| pH, Total Alkalinity      | Daniela Nestory           | *UCSD*                    | dnestory@ucsd.edu         |
+---------------------------+---------------------------+---------------------------+---------------------------+
| pH, Total Alkalinity      | Carmen Rodriguez          | *U Miami*                 | crodriguez@rsmas.miami.e  |
|                           |                           |                           | du                        |
+---------------------------+---------------------------+---------------------------+---------------------------+
| pH, Total Alkalinity      | Albert Ortiz              | *U Miami*                 | albert.ortiz@rsmas.miami  |
|                           |                           |                           | .edu                      |
+---------------------------+---------------------------+---------------------------+---------------------------+
| *DOC*, *TDN*              | Chance English            | *UCSB*                    | cje@ucsb.edu              |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Marine Technician         | Stephen Jalickee          | *UW*                      | jalickee@uw.edu           |
+---------------------------+---------------------------+---------------------------+---------------------------+
| Marine Technician         | Elizabeth Ricci           | *UW*                      | ericci@uw.edu             |
+---------------------------+---------------------------+---------------------------+---------------------------+


Cruise Narrative
================

   [image]GO-SHIP A22 2021 occupation. Black dots are used for
   CTD/LADCP/rosette stations in the Caribbean Sea, red in the Anegada
   Passage, blue along 66W and pink following the Line-W. PR stands
   for Puerto Rico.

The A22 2021 occupation (Figure 1) followed the 2012 transect, except
that nine stations were added in the region between the south of
Puerto Rico and Bermuda. These additional stations made the nominal
spacing for the 2021 occupation about 30 nm (50 km) in the open ocean.
Like 2012, stations were more spaced (more than 40- nm) in two areas:
around Puerto Rico and Bermuda because the sea is very shallow there
(< 50 m). The initial cruise length (28-days) was planned so that
there were two weather days if a weather system put CTD operations on
hold. Previous occupations of this transect were impacted by weather
systems. In 2012, a similar period (April-May) as 2021, a weather
system delayed operation at the beginning of the cruise. As explained
below, the weather was not a problem in 2021; all 90 planned stations
were successfully occupied, with the full suite of core GO-SHIP
chemical and physical parameters measured from the sea surface to 10 m
above the seafloor (as described in the following sections). The A22
2021 cruise had a total duration of 27 days.

In contrast to 2012, the A22 started at its most equatorial position
(12.6N-70W) and ran northward. We departed from St. Thomas
(18.3N-64.9W), US Virgin Island, on April 20 and arrived in Woods Hole
(41.5N-70.7W), Massachusetts, on May 16, a day earlier than initially
predicted due to excellent weather and a faster transit speed than
anticipated (sustained 13 knots). The A22 was occupied immediately
after the A20 (~52W), which started in Woods Hole, Massachusetts, and
worked towards St. Thomas.

Because of the COVID-19 pandemics, we had fewer participants during
the A20/A22 journey, each leg with a science party of twenty-five
members. The smaller science party decreased our ability to take
level-3 measurements in these legs compared with previous (pre-COVID)
GO-SHIP cruises. More than half (14 members) participated on both
cruises totalizing more than 2-months at sea.

As part of the COVID-19 protocol, all members had to self-isolate in a
facility for two weeks, take several COVID tests, measure body
temperature twice a day (recording them online), and wear face masks.
Twelve people observed isolation in St. Thomas, including the chief
and co-chief scientists for the A22. One of the members broke the
COVID protocol by walking outside the isolation property without a
mask and could not come on board. In total, each member isolating at
St. Thomas took 4 to 5 tests: before traveling to St. Thomas (1-2), at
St. Thomas (2), and before board the ship (1). All 11 members were
negative for COVID-19 and allowed to board R/V Thompson. During the
first two weeks of the cruise, all participants wore masks outside
their staterooms, kept social distance (only two people per table were
allowed during meal times), and continued to monitor their body
temperature through the cruise. With this strict protocol being
followed by all, no COVID case was registered in both A20 and A22.

The R/V Thompson departed from St. Thomas, US Virgin Island on April
20, 08:00 AST. The transit to the first station near South America was
short (about 1.75 days). While in transit, early on April 21, the
first Core Argo float (~15.27N-69.06W) was deployed. A test station
was done in international waters (4700 m deep) to train the CTD watch-
standers and incoming lab technicians. For the test station, noon time
was chosen so both watches could participate it. The first cast had to
be aborted as a cap was not removed. This was the only time during the
A22 that a cast was aborted. The package was redeployed after bringing
it back to the deck to remove the cap. Later, it was determined that
the UVP did not restart on the redeployment, but the decision was made
to continue with the cast. No further incident with UVP happened for
the entire cruise. During the test station, the CTD watch-standers
learned from the ODF technicians how to prepare the rosette, fill in
the logs, make a bottom approach, and fire the bottles. It was a slow
cast as everybody was learning, and mistakes were being corrected. All
36 bottles were fired, giving the CTD watch-standers as much
experience as possible before beginning the first part of the A22 line
where stations were close together (< 10 nm in the Caribbean Current).

We arrived at the first station in the early hours of April 22.
Throughout the next 24-hours, 7 stations were occupied in the
Caribbean Current. The next day, we slowed the pace between stations
(even waiting on), from 2h to 2.5h, to give more time for equipment
charging (LADCP and UVP) and lab analysis. This procedure was adopted
throughout the cruise. In every segment with stations closer than 20
nm, the time between casts was set to 2.5 or 3h depending on whether
it was a half/full carbon station. This allowed the labs to take and
analyze samples as much as possible, resulting in more complete
datasets. Full carbon stations mean that carbon parameters samples are
taken from all Niskin bottles. On partial stations (depending on how
backed-up analysis is), samples are collected from about half bottles.
Bottles on partial stations were selected to capture good vertical
resolution. Most skipped bottles were in deep waters where DIC change
is much smaller than in upper layers. At the 2021 A22 occupation, even
stations were full carbon, and odds partial.

Time for lab analysis is an important parameter that should be
considered in future GO-SHIP cruise planning. One thing that worked
well was always keeping the labs informed about the time of arrival at
stations for the next two/three days ahead. This helped the techs to
plan the sampling better, as many of them have expressed. For
estimating the time of arrival at stations, we used the Matlab
routines from Alison Macdonald (WHOI), who kindly shared with us. We
adapted the routines to the A22 specificities– everything worked well
and avoid sample analysis falling behind schedule.

The weather was good, and the sea was flat most of the time during the
2021 occupation, except by a single day (May 10, 2021). Typically,
winds were around 10 to 15 m/s along the A22 (Figure 2). The only time
the winds peaked above 35 m/s was on May 10, when CTD operation was
put on hold for almost a day during station #73. This was the single
weather day for all cruise. Thanks to the weather forecast, we knew
well in advance that the ship would face strong winds and high waves.

   [image]Real-time winds during the GO-SHIP A22 2021 occupation. Left
   is a typical day with wind strength varying from 10-20 m/s. Right
   is the winds for May 10 when the CTD operations were put on hold.

The good weather and flat sea made CTD deployments straightforward
during the 2021 occupation (Figure 3). Only minor issues happened as
documented later in this report: few unfired bottles, a broken O-ring,
a missed target depth, wrong numbers in the sample log, and LADCP
cable connections. These issues were sporadic and immediately fixed.
Besides these minor issues, two mild injuries happened during rosette
preparation, which led us to double our attention as a precaution. The
injuries were a slight concern through the cruise, although everybody
was well.

   [image]Flat sea and fair winds during GO-SHIP A22 2021 occupation.
   Left on May 3 and Right on May 15.

All 16 floats and 19 spotter buoys were deployed after stations with a
ship speed of a few knots. All of them were successfully deployed by
the CTD watchstanders and R/V Thompson marine technicians, as later
described. For the Go-BGC floats, the deployments were chosen to match
full carbon stations. This decision was taken to avoid disrupting the
vertical sampling scheme of carbon parameters and at the same time to
have enough depths between the surface and 2000 m to compare with
these floats.

Sargassum samples, a piggy-back project during the A22 2021, were also
collected when stations were in the US EEZ (exclusive economic zone)
or international waters. This work was conducted by the ABs
coordinated by the chief-mate.


Principal Finding and Features
------------------------------

The A22 transect occupied the western North Atlantic, extending from
South America to the continental shelf of the Cape Cod. Along the way,
it crossed main water masses of the North Atlantic (Figure 4): a
strong signal of Antarctic Intermediate Water (AAIW) at the Caribbean
Sea, a vestige of Antarctic Bottom Water (AABW) north of Puerto Rico
(\gamma = 28.162 kg/m^3), the salty Subtropical Underwater (STUW) from
the Caribbean Sea to 23-25ºN, several types of North Atlantic Deep
Water (NADW) north of 30ºN and mixed waters of the Slope Sea, north of
the Gulf Stream.

   [image]Temperature-Salinity diagram for the A22 2021 occupation.
   Color shows the latitude and contours potential density anomaly
   (kg/m^3). Map displays the A22 transect in the western North
   Atlantic. Water mass classification based on neutral density
   (\gamma) as defined by Joyce et al. (2001)

In the Caribbean Sea, the water mass distribution was similar to the
previous occupations. No significant change in properties in the deep
ocean was observed compared to 2012 (Figure 5). But, there was slight
warming and salinification over the entire basin at those depths.
Between 100-300 m, the saline STUW (with salinity > 37) was easily
spotted in all stations in the Caribbean (Figure 6). The STUW
continued to be spotted north of Puerto Rico until 25ºN (Figure 6,
upper panel).

The fingerprint of AAIW (low salinity and low oxygen in the North
Atlantic) was also present between 600-1000 m in the Caribbean (Figure
6). The AAIW enters the Caribbean basin through the Anegada Passage.
Two stations were realized there during 2021, instead of one as in
2012. In both stations, there was a clear AAIW signal. As in 2012, the
AAIW signature was intensified near South America, and its signature
faded outside the Caribbean.

Like 2012, the water column was well mixed and weakly stratified in
the Caribbean Sea below 2000 m (Figure 6). No strong density front or
mesoscale eddies could be identified in the density field at the upper
layer. Between 1500-2500, slightly slanted isopycnals were noticeable
near Puerto Rico (Figure 6, lower left panel), probably associated
with the Caribbean deep cyclonic gyre described by [Joyce2001] based
on the 1997 A22 occupation.

The thermohaline front associated with the Gulf Stream was apparent at
the end of the section (Figure 6). The Gulf Stream was particularly
strong, with speeds measured by the shipboard ADCP of about 2.2 m/s in
its core. Concurrent altimetry measurements (Figure 7) slightly
underestimated it, with a maximum speed of 1.7 m/s.

Compared with 2012, cooling in the deep ocean was observed north of
Puerto Rico, where the DWBC passes (Figure 5). This was accompanied by
a slight freshening. Below 4500, where a vestige of AABW was detected,
the cooling seems to be intensified. As a result, there was an uplift
of \gamma = 28.15 by about 200 m in the water column. CFCs
measurements (not shown) also suggest changes north of Puerto Rico. In
2012, it was found an eddy with unusual water properties, near 21.5°N,
just north of the Puerto Rico Trench. The property anomalies - high
oxygen and CFCs, low salinity, and nutrients – were particularly
strong between 1000-1500 meters depth. It was suggested that this eddy
originated to the east of Newfoundland. In 2021, the eddy was not
present.

   [image]Difference in potential temperature (left) and salinity
   (right) between 2021 and 2012 A22 occupations. Contours are neutral
   density in 2021 (black) and 2012 (blue).

   [image]Potential temperature (upper left) and salinity (upper
   right) distributions at A22 2021 (stations 1-90) from CTD data.
   Same for neutral density (lower left) and dissolved oxygen (lower
   right). Contours are \gamma = 26, 27, 27.6, 27.9, 28.1, and 28.15
   kg/m^3.

   [image]Geostrophic velocities for May 11 from satellite altimeters
   and A22 stations (dots).

[Joyce2001] Joyce, T. M., Hernandez‐Guerra, A., and Smethie, W. M.
            (2001), Zonal circulation in the NW Atlantic and Caribbean
            from a meridional World Ocean Circulation Experiment
            hydrographic section at 66°W, J. Geophys. Res., 106( C10),
            22095– 22113, doi:10.1029/2000JC000268.


CTD and Rosette Setup
=====================

For A22-2021 the new STS 36 place yellow rosette and bottles, built in
2017, were used. The rosette and bottles were built before P06 2017,
making this the seventh time this package has been deployed. The
bottles were made with new PVC, with new non-baked o-rings and
electro-polished steel springs. This represents a change from the
past, where on GO-SHIP cruises using ODF equipment before P06 2017
o-rings were baked for 3 days at 100°C at 1-3 Torr in a sweeper gas of
hydrogen. Springs used to be painted and Tygon tubing added to the
ends to prevent paint wearing away from bottle firing. As on P06 2017
no sample contamination has been noticed by the change in o-rings and
springs. The package used on A22-2021 weighs roughly 1500 lbs in air
without water, and 2350 lbs in air with water. The package used on
A22-2021 weighs roughly 950 lbs in water. In addition to the standard
CTDO package on GO-SHIP cruises three chipods, two LADCPs, and one
experimental CTD were mounted on the rosette. During the cruise we
encountered a handful of problems, most notably noisy altimeter data
and bottle firing issues. We describe all of the above in more detail
in the sections below.


Underwater Sampling Package
---------------------------

CTDO/rosette/LADCP/UVP/chipod casts were performed with a package
consisting of a 36 bottle rosette frame, a 36-place carousel and 36
Bullister style Niskin bottles with an absolute volume of 10.6L.
Underwater electronic components primarily consisted of a SeaBird
Electronics housing unit with Paroscientific pressure sensor with dual
plumbed lines where each line has a pump, temperature sensor,
conductivity sensor, and exhaust line. A SeaBird Electronics membrane
oxygen sensor was mounted on the “primary” line. A reference
thermometer, Rinko oxygen optode, transmissometer, chlorophyll-a
fluorometer, and altimeter were also mounted on the rosette. Chipod,
LADCP, and UVP instruments were deployed with the CTD/rosette package
and their use is outlined in sections of this document specific to
their titled analysis.

CTD and cage were horizontally mounted at the bottom of the rosette
frame, located below the carousel for all stations. The temperature,
conductivity, dissolved oxygen, respective pumps and exhaust tubing
was mounted to the CTD and cage housing as recommended by SBE. The
reference temperature sensor was mounted between the primary and
secondary temperature sensors at the same level as the intake tubes
for the exhaust lines. The transmissometer was mounted horizontally on
the lower LADCP brace with hose clamps around both of its ends,
avoiding shiny metal or black tape inside that would introduce noise
in the signal. The oxygen optode, fluorometer, and altimeter were
mounted vertically inside the bottom ring of the rosette frames, with
nothing obstructing their line of sight. One 300 KHz bi-directional
Broadband LADCP (RDI) unit was mounted vertically on the bottom side
of the frame. Another 300 KHz bi-directional Broadband LADCP (RDI)
unit was mounted vertically on the top side of the frame. The LADCP
battery pack was also mounted on the bottom of the frame. The LADCP
and LADCP battery pack were mounted next to each other at the
beginning of the cruise. If we imagine the LADCP battery being north
on the rosette, the LADCP was mounted east, the CTD mounted south, and
the UVP mounted west.

+------------------+------------------+------------------+------------------+------------------+------------------+
| Equipment        | Model            | S/N              | Cal Date         | Stations         | Group            |
|==================|==================|==================|==================|==================|==================|
| Rosette          | 36-place         | Yellow           | –                | 901-90           | *STS*/*ODF*      |
+------------------+------------------+------------------+------------------+------------------+------------------+
| CTD              | SBE9+            | 0914             | –                | 901-90           | *STS*/*ODF*      |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Pressure Sensor  | Digiquartz       | 110547           | Feb 5, 2021      | 901-90           | *STS*/*ODF*      |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Primary          | SBE3+            | 32309            | Feb 2, 2021      | 901-90           | *STS*/*ODF*      |
| Temperature      |                  |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Primary          | SBE4C            | 43399            | Nov 25, 2020     | 901-90           | *STS*/*ODF*      |
| Conductivity     |                  |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Primary Pump     | SBE5             | 51871            | –                | 901-90           | *UCSD*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Secondary        | SBE3+            | 32380            | Feb 2, 2021      | 901-90           | *STS*/*ODF*      |
| Temperature      |                  |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Secondary        | SBE4C            | 41880            | Dec 4, 2020      | 901-90           | *STS*/*ODF*      |
| Conductivity     |                  |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Secondary Pump   | SBE5             | 58690            | –                | 901-90           | *UCSD*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Transmissometer  | Cstar            | 1803DR           | Aug 9, 2019      | 901-90           | *TAMU*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Fluorometer      | WetLabs ECO-FL-  | 1156             | –                | 901-90           | *STS*/*ODF*      |
| Chlorophyll      | RTD              |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Dissolved Oxygen | SBE43            | 430255           | Nov 13, 2020     | 901-90           | *ODF*            |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Oxygen Optode    | JFE Advantech    | 0296             | Apr 7, 2017      | 901-90           | *ODF*            |
|                  | Rinko-III        |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Reference        | SBE35            | 0105             | Feb 9, 2021      | 901-90           | *STS*/*ODF*      |
| Temperature      |                  |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Carousel         | SBE32            | 0187             | –                | 901-43           | *STS*/*ODF*      |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Carousel         | SBE32            | 1178             | –                | 44-90            | *STS*/*ODF*      |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Altimeter        | Valeport 500     | 53821            | –                | 901-59, 61-90    | *UCSD*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Altimeter        | Valeport 500     | 48049            | –                | 60               | *UCSD*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| DL *LADCP*       | Teledyne RDI     | 24497            | –                | 901-90           | *LDEO*           |
|                  | WH300            |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| UL *LADCP*       | Teledyne RDI     | 12734            | –                | 901-90           | *LDEO*           |
|                  | WH300            |                  |                  |                  |                  |
+------------------+------------------+------------------+------------------+------------------+------------------+
| UVP              | –                | 207              | –                | 901-90           | *UAF*            |
+------------------+------------------+------------------+------------------+------------------+------------------+
| D2 CTD           | D2 CTD           | 01-1563          | –                | 901-45           | *WHOI*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| D2 CTD           | D2 CTD           | 01-1565          | –                | 46-90            | *WHOI*           |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Chipods          | Chipod           | 2008 Ti44-5      | –                | 901-90           | *OSU*            |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Chipods          | Chipod           | 2027 TI44-3      | –                | 901-90           | *OSU*            |
+------------------+------------------+------------------+------------------+------------------+------------------+
| Chipods          | Chipod           | 2030 Ti44-11     | –                | 901-90           | *OSU*            |
+------------------+------------------+------------------+------------------+------------------+------------------+

   [image]Package sensor setup from south.

   [image]Package sensor setup from east.

   [image]Package sensor setup from north.

   [image]From left to right: oxygen optode, fluorometer, LADCP
   battery pack, altimeter.

   [image]Package setup from southwest, with CTD in foreground and
   downlooking chipod to the right.

   [image]Packaget setup from west.

   [image]Package  setup from west, top view.


Winch and Deployment
--------------------

The aft DESH-5 winch deployment system was used for all stations. The
rosette system was suspended from a UNOLS-standard three-conductor
0.322” electro-mechanical sea cable. The sea cable was already
terminated from the previous leg (A20) and no electrical or mechanical
issues occurred on A22.

The deck watch prepared the rosette 10-30 minutes prior to each cast.
The bottles were cocked and all valves, vents, and lanyards were
checked for proper orientation. Any biofouling noted was cleaned off
the outside of the rosette before the next cast, and the inside of the
bottles were checked for biofouling and sprayed down. LADCP technician
would check for LADCP battery charge, prepare instrument for data
acquisition, and disconnect cables. Once stopped on station, the
Marine Technician would check the sea state prior to cast and decide
if conditions were acceptable for deployment. The rosette was moved
from the sampling bay out to the deck using the Thompson’s new winch-
driven cart. Once on deck, the ratchet straps connecting the rosette
to the cart were removed and sea cable slack was pulled up by the
winch operator. CTD watch standers would then turn on the deckbox and
begin data acquistion, and the cast would begin. Recovering the
package at the end of the deployment was the reverse of launching.
Once rolled back into the sampling bay, the ship crew secured the cart
to the deck using additional ratchet straps. The carousel was rinsed
and sensors were cleaned (as described below) after every cast, and
then samplers were allowed to begin collecting water.


Maintenance and Calibrations
----------------------------

During A22-2021 routine maintenance was done to the rosette to ensure
quality of the science done. Actions taken included rinsing all
electrical instruments on the rosette down with fresh water after each
cast and adjusting hose clamps and guide rings as needed such that
lanyards had appropriate tension. Care was taken not to rinse the
spigots and other parts of the bottle that might be touched by
samplers in order to not contaminate the samples. After each cast,
syringes of fresh water were connected to the plumbed lines to rinse
the sensors and allow them to soak between casts. While in freezing
conditions, water was drained after rinse to avoid freezing in the
plumbing. Overhead heaters recently installed on the Thompson were run
while in freezing or near-freezing conditions. The rosette was
routinely examined for valve and o-ring leaks, which were maintained
as needed. SBE35RT temperature data was routinely downloaded each day.

Every 20 stations, the transmissometer windows were cleaned and on
deck blocked and un-blocked voltage readings were recorded prior to
the cast. The transmissometer was also calibrated before the start and
after the end of science operations.


Logs
----

In port: Preparation of the CTD and rosette was minimal as it had
nearly the same setup as A20 2021, which had just been completed. UVP
arrived in St. Thomas and was mounted opposite the ADCP. Downlooking
chipod mounting pole was swapped out to allow the sensor to be closer
to the leading edge of the rosette. Additional integrity checks on the
rosette, such as checking lanyard angles, o-ring and lanyard
replacement, and spigot movement waited until being underway to be
checked as lower priority tasks. We are using a new mounting system
for the downward looking LADCP which has the LADCP clamped facing
inward instead of outward, which will cause problems if we need to
change that LADCP in rough weather.

April 21, 2021

90001 – First test cast aborted around 350 m. Tube connecting the
primary and secondary pumps (attached in port to prevent fouling of
the plumbing lines) was not removed prior to start of cast, identified
initially in data by large differences in primary/secondary T/C lines.

90002 – Test cast to 4500 m. UVP did not turn on during ascent from
initial 20 m soak. Tried soaking again (at 20 m), still did not
activate. Upon recovery, data from cast 90001 was present but nothing
was recoreded from 90002. The assumption is that the rosette was not
on deck long enough to fully power cycle the UVP.

April 22, 2021

00101 – UVP turned on as expected; no issues noted. Adjusted guide
ring on bottle 30.

00201 – Bottles 4, 5, 6, and 9 were leaking, 11 and 12 had loose
vents.

00301 – Fired surface bottle (#23) on the fly due to large swell.
Rosette sat at 35 m for longer than standard while deck crew prepared
for recovery.

00401 – Adjusted guide ring on bottles 29, 30, 32 before cast.

00501 – No issues noted.

00601 – No issues noted.

April 23, 2021

00701 – Bottle 25 did not close, top cap was stuck against rosette
frame crossbar. Entire bottle was moved downward to prevent that from
happening again.

00801 – No issues noted.

00901 – No issues noted.

01001 – ADCP data reported in multiple files, suspected power issues.
Swapped out cable and battery.

April 24, 2021

01101 – No issues noted.

01201 – Bottle 3 did not fire.

01301 – No issues noted.

01401 – Surface bottle (#36) was too cold, closer to temperature of
400-500 m bottles. Inspecting after cast, the bottom end cap was loose
enough to close itself, likely early closure. Adjusted guide ring to
prevent early closures.

April 25, 2021

01501 – No issues noted.

01601 – Adjusted guide ring for bottle 32 before cast.
Miscommunication with winch during bottom approach: stopped early (~20
m from bottom), fired bottle as normal, after which winch continued
downward briefly. On way up, bottle 2 was misfired shortly after
leaving the bottom.

01701 – No issues noted.

01801 – No issues noted.

April 26, 2021

No issues noted for stations 01901-02101.

April 27, 2021

02201 – No issues noted.

02301 – No issues noted.

02401 – ~160 m salnity spike (just primary line?)

02501 – No issues noted.

02601 – No issues noted.

02701 – Taking less than half a rosette worth of bottles, fired odd
bottles to make recovery easier (uniformly distributed weight instead
of all to one side). Was confusing for analysts in other groups, will
not do again.

02801 – 115 m depth bottle mistakenly skipped, shifted remaining
bottles appropriately.

April 28, 2021

02901 – No issues noted.

03001 – Adjusted guide rings on 2, 10, 12, 14, 19, 32-36 before cast.

03201 – Raised bottle 26 up before cast, may have been firing late
because of poor placement.

03301 – Bottle 3 did not close.

April 29, 2021

03401 – Bottle 22 did not close. Adjusted bottle 23 height since it
was getting stuck on crossbar.

03501 – Bottle 3 did not close. Replaced carouse latch for bottle 33
and raised bottle 22 to improve lanyard angle.

03601 – Adjusted guide ring son bottle 2, 8, 9, 17, 19, 21, 24.

03701 – Air vent on bottle 35 was not fully shut.

April 30, 2021

03801 – Salinity signal was a little spiky during soak but quickly
remedied itself (may just be bottom of mixed layer or something pulled
through lines?).

03901 – Bottle 26 guide ring adjusted upward.

04001 – No issues noted.

May 1, 2021

04101 – Bottle 3 did not fire, bottle 16 was leaking due to loose air
vent. Bottle 26 accidentally misfired on fly.

04201 – Bottle 3 did not fire.

04301 – Adjusted guide rings on bottles 17-21, 23, 32. Skipped firing
bottle 3, will repair “spare” (i.e. primary) carousel during cast and
replcae during transit to next.

May 2, 2021

04401 – Adjusted guide ring on bottle 15. Replaced carousel with
primary, after swapping solenoid #12.

04501 – No issues noted.

04601 – D2 1563 replaced with 1565 at PI’s request. Adjusted guide
rings on bottles 11, 15, 19, 21, 23, 29, 30, 33, and 35. UVP did not
show much change in surface during soak but was fine during cast;
suspected the upper water column did not have much to photograph.

04701 – Downlooking chipod was remounted with thicker rubber between
unistruct and frame, hoping to stop the shifting which is occurring
during deployment, cast, or recovery.

May 3, 2021

04801 – Spigot on bottle 35 was not fully closed.

04901 – Altimeter spiking during bottom approach.

05001 – Replaced spigot o-rings for bottle 16 before cast, was sticky
and hard to fully close. Altimeter continuing to be spiky during
bottom approach.

May 4, 2021

05101 – Bottle 35 was leaking, broken air vent o-ring – replaced
before next cast. Also replaced for bottles 5, 7, and 9.

05201 – Altimeter continuing to be spiky during bottom approach.

05301 – Adjusted guide rings on 18, 29-34 before cast. Altimeter did
not kick in until ~50 m from bottom, then was noisy during the entire
bottom approach; stopped ~20 m from bottom to be conservative. Bucket
testing afterward did not reveal any obvious problems and comparison
with a new (presumably function) altimeter had the same results.

05401 – Adjusted guide rings on 8, 10, 36. Same altimeter behavior.

May 5, 2021

05501 – Same altimeter behavior. Will leave as is since the behavior
is now predictable, rather than introduce new unknowns. Bottle 25
fired quickly after stop, rather than waiting 30 seconds. Spigot pull
tab on bottle 6 broken on recovery.

05601 – Same altimeter behavior.

05701 – Replaced o-rings and broken pull tab on bottle 6 before cast.

May 6, 2021

05801 – Spiky transmissometer data, tape on hose clamp came loose.
After cast, wrapped electrical tape in a spiral around hose clamp to
prevent it from peeling up.

05901 – Altimeter seems to be getting worse, swapping in TGT’s 48049
before cast 60.

06001 – Adjusted guide rings on 10, 18, 20, 24, 29-33, 35, 36.
Altimeter not much different. Swapping back to original (S/N 53821)
and also swapping to TGT’s cable to see if that is the issue.

06101 – Altimeter behavior largely the same. Ultimately decided noise
is due to rosette angle and bathymetry scattering the pings, the
effect of which is reduced closer to the bottom.

May 7, 2021

06201 – Transmissometer spike ~1130 m.

06301 – Adjusted guide rings on the usual bottles. After cinching down
with drill, tightened every hose clamp further with a screwdriver. Was
able to get at least 1/4 turn out of each, drill not as powerful as it
used to be?

06401 – No issues noted.

May 8, 2021

06501 – Raining heavily during deployment.

06601 – No issues noted.

06701 – No issues noted.

May 9, 2021

06801 – No issues noted.

06901 – Rubber between top bottle standoff sliding out, removed after
cast. Hose clamp was not tightened down so bottle was a little loose.

07001 – At 5 m bottle stop, there was a miscommuncation and the ship
rotated to face into the swell. Rotated before bottle fired so sample
is highly contaminated.

07101 – Tighted all guide ring hose clamps with screwdriver once
again.

May 10, 2021

07201 – No issues noted.

Weather delay for the rest of the day.

May 11, 2021

07301 – Changed top end cap, lanyards contected to it, and o-ring.
Miscommunication between shifts led to the interior lanyard (cap to
spring) to be changed again.

07401 – No issues noted.

07501 - Bottle 29 vent was not fully closed.

May 12, 2021

07601 – Bottle 2 did not seal all the way, o-ring not well seated –
o-ring replaced by night shift (miscommuncation again, o-ring was just
recently changed). Inter-lanyards (cap to cap) replaced on bottles 28
and 29.

07701 – Bottle 2 o-ring not well seated again, may have questionable
data. Tried to remove any twist in o-ring and re-seat. Gulf Stream
currents very strong, large wire angle.

07801 – Inter-lanyard (cap to cap) for bottle 29 was very tight upon
recovery, removed shortly after getting on deck. Old one was ~1.5” too
short – replaced with a new one of appropriate length before cast 79.
Bottle 2 o-ring unseated again, replaced end cap with original one
that was working properly.

May 13, 2021

07901 – ADCP having trouble turning on, cast slightly delayed. Rosette
drifted upward during bottom bottle stop.

08001 – No issues noted.

08101 – Adjusted guide ring 23, tightened all others with screwdriver.
Spigot on bottle #16 is very sticky, replaced before cast 82.

08201 – No issues noted.

May 14, 2021

08301 – No issues noted.

08401 – No issues noted.

08501 – Mixed layer shallow, no good spot to switch to auto-cast.

08601 – Trying bottle stop experiment, fired triplicates at 30, 60,
and 90 seconds after stop, at two depths.

08701 – No issues noted. Trying bottle stop experiment, fired
triplicates at 30, 60, and 90 seconds after stop, at two depths.

May 15, 2021

08801 – Trying bottle stop experiment, fired triplicates at 30, 60,
and 90 seconds after stop, at two depths.

08901 – No issues noted.

09001 – No issues noted.


Sensor Problems
---------------

*SBE 32 Carousel*: Another solenoid failure, this time in secondary
carousel. Primary was fixed and swapped in on before cast 44. Pictures
of swollen solenoid shown below.

   [image]Bad solenoid (center), cloudy and raised edge from
   corrosion.

   [image]Bad solenoid (left), cloudy and raised edge from corrosion.

*Altimeter spiking*: Ended up just being bathymetry/bad returns.
Swapping altimeter and cables made no difference.

*Bottle guide rings*: Guide rings continually slipped during the whole
cruise. In the end, the issue was they were not being sufficiently
tightened by the normal drill we used – fixed by hand tightening
further with screwdriver.


CTDO and Hydrographic Analysis
==============================

PIs
   * Susan Becker (SIO)

   * James Swift (SIO)

Technicians
   * Michael Kovatch (SIO)


CTDO and Bottle Data Acquisition
--------------------------------

The CTD data acquisition system consisted of an SBE-11+ (V2) deck unit
and a networked generic PC workstation running Windows 10. SBE
SeaSave7 v.7.26.7.107 software was used for data acquisition and to
close bottles on the rosette.

CTD deployments were initiated by the console watch operators (CWO)
after the ship had stopped on station. The watch maintained a CTD cast
log for each attempted cast containing a description of each
deployment event and any problems encountered.

Once the deck watch had deployed the rosette, the winch operator would
lower it to 10 meters. The CTD sensor pumps were configured to start
10 seconds after the primary conductivity cell reports salt water in
the cell. The CWO checked the CTD data for proper sensor operation,
waited for sensors to stabilize, and instructed the winch operator to
bring the package to the surface in good weather or no more than 5
meters in high seas. The winch was then instructed to lower the
package to the initial target wire-out at no more than 30 m/min for
the first 100 m and no more than 6 0m/min after 100 m depending on
sea-cable tension and the sea state.

The CWO monitored the progress of the deployment and quality of the
CTD data through interactive graphics and operational displays. The
altimeter channel, CTD pressure, wire-out and center multi-beam depth
were all monitored to determine the distance of the package from the
bottom. The winch was directed to slow decent rate to 30 m/min 100 m
from the bottom. The bottom of the CTD cast was usually to within
10-20 meters of the bottom determined by altimeter data. For each
upcast, the winch operator was directed to stop the winch at up to 36
predetermined sampling pressures. These standard depths were staggered
every station using 3 sampling schemes. The CTD CWO waited 30 seconds
prior to tripping sample bottles, to ensure package had shed its wake.
An additional 15 seconds elapsed before moving to the next consecutive
trip depth, which allowed for the SBE35RT to record bottle trip
temperature averaged from 13 samples.

After the last bottle was closed, the CWO directed winch to recover
the rosette. Once the rosette was out of the water and on deck, the
CWO terminated the data acquisition, turned off the deck unit and
assisted with rosette sampling.

Additionally, the watch created a sample log for the deployment which
recorded the depths bottles were tripped and correspondence between
rosette bottles and analytical samples drawn.

Normally the CTD sensors were rinsed after each station using syringes
of fresh water connected to Tygon tubing. The tubing was left on the
CTD between casts, with the temperature and conductivity sensors
immersed in fresh.

Each bottle on the rosette had a unique serial number, independent of
the bottle position on the rosette. Sampling for specific programs
were outlined on sample log sheets prior to cast recovery or at the
time of collection. The bottles and rosette were examined before
samples were drawn. Any abnormalities were noted on the sample log,
stored in the cruise database and reported in the APPENDIX.


CTDO Data Processing
--------------------

Shipboard CTD data processing was performed after deployment using
SIO/ODF CTD processing software “ctdcal” v. 0.1. CTD acquisition data
were copied onto a OS X system, and then processed. CTD data at bottle
trips were extracted, and a 2-decibar downcast pressure series
created. The pressure series data set was submitted for CTD data
distribution after corrections outlined in the following sections were
applied.

A total of 90 CTD stations were occupied including one test station. A
total of 91 CTDO/rosette/LADCP/UVP/chipod casts were completed.

CTD data were examined at the completion of each deployment for clean
corrected sensor response and any calibration shifts. As bottle
salinity and oxygen results became available, they were used to refine
conductivity and oxygen sensor calibrations.

Temperature, salinity and, dissolved O_2 comparisons were made between
down and upcasts as well as between groups of adjacent deployments.
Vertical sections of measured and derived properties from sensor data
were checked for consistency.

A number of issues were encountered during A22-2021 that directly
impacted CTD analysis. Issues that directly impacted bottle closures,
such as slipping guide rings, were detailed in the Underwater Sampling
Package section of this report. Temperature, conductivity, and oxygen
analytical sensor issues are detailed in the following respective
sections.


Pressure Analysis
-----------------

Laboratory calibrations of CTD pressure sensors were performed prior
to the cruise. Dates of laboratory calibration are recorded on the
underway sampling package table and calibration documents are provided
in the APPENDIX.

The lab calibration coefficients provided on the calibration report
were used to convert frequencies to pressure. Initial SIO pressure lab
calibration slope and offsets coefficients were applied to cast data.
A shipboard calibration offset was applied to the converted pressures
during each cast. These offsets were determined by the pre and post-
cast on-deck pressure offsets. The pressure offsets were applied per
cast.

CTD #0914:

+-----------------------------------+-----------------------------------+-----------------------------------+
|                                   | Start P (dbar)                    | End P (dbar)                      |
|===================================|===================================|===================================|
| Min                               | -0.20                             | -0.28                             |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Max                               | 0.05                              | -0.08                             |
+-----------------------------------+-----------------------------------+-----------------------------------+
| Average                           | 0.09                              | -0.19                             |
+-----------------------------------+-----------------------------------+-----------------------------------+

On-deck pressure reading varied from -0.20 to 0.05 dbar before the
casts, and -0.28 to -0.08 dbar after the casts. The pressure offset
varied from -0.24 to 0.09, with a mean value of -0.1 dbar.


Temperature Analysis
--------------------

Laboratory calibrations of temperature sensors were performed prior to
the cruise at the SIO Calibration Facility. Dates of laboratory
calibration are recorded on the underway sampling package table and
calibration documents are provided in the APPENDIX.

The pre-cruise laboratory calibration coefficients were used to
convert SBE3plus frequencies to ITS-90 temperature. Additional
shipboard calibrations were performed to correct systematic sensor
bias. Two independent metrics of calibration accuracy were used to
determine sensor bias. At each bottle closure, the primary and
secondary temperature were compared with each other and with a SBE35RT
reference temperature sensor.

The SBE35RT Digital Reversing Thermometer is an internally-recording
temperature sensor that operates independently of the CTD. The SBE35RT
was located equidistant between the two SBE3plus temperature sensors.
The SBE35RT is triggered by the SBE32 carousel in response to a bottle
closure. According to the manufacturer’s specifications, the typical
stability is 0.001°C/year. The SBE35RT was set to internally average
over 13 samples, approximately a 15 second period.

A functioning SBE3plus sensor typically exhibit a consistent
predictable well-modeled response. The response model is second-order
with respect to pressure and second-order with respect to temperature:

   T_{cor} = T + cp_2 P^2 + cp_1 P + ct_2 T^2 + ct_1 T + c_0

Fit coefficients are shown in the following tables.


Primary temperature (T1) coefficients.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+------------------+------------------+------------------+------------------+------------------+------------------+
| Station          | cp_2             | cp_1             | ct_2             | ct_1             | c_0              |
|==================|==================|==================|==================|==================|==================|
| 901-29           | 9.127e-11        | -7.1661e-7       | 0.0              | 0.0              | 4.7065e-4        |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 30-72            | 8.4036e-11       | -8.6330e-7       | 0.0              | 0.0              | 1.1989e-3        |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 73-90            | -4.6532e-11      | 1.2251e-7        | 0.0              | 0.0              | -8.1808e-4       |
+------------------+------------------+------------------+------------------+------------------+------------------+


Secondary temperature (T2) coefficients.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+------------------+------------------+------------------+------------------+------------------+------------------+
| Station          | cp_2             | cp_1             | ct_2             | ct_1             | c_0              |
|==================|==================|==================|==================|==================|==================|
| 901-29           | 0.0              | -2.1424e-7       | 0.0              | 0.0              | -1.4331e-4       |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 30-72            | 0.0              | -8.1227e-8       | 0.0              | 0.0              | -6.3841e-4       |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 73-90            | 0.0              | -1.3354e-7       | 0.0              | 0.0              | -7.2422e-4       |
+------------------+------------------+------------------+------------------+------------------+------------------+

Corrected temperature differences are shown in the following figures.

   [image]SBE35RT-T1 versus station.

   [image]Deep SBE35RT-T1 by station (Pressure \geq 2000dbar).

   [image]SBE35RT-T2 versus station.

   [image]Deep SBE35RT-T2 by station (Pressure \geq 2000dbar).

   [image]T1-T2 versus station.

   [image]Deep T1-T2 versus station (Pressure \geq 2000dbar).

   [image]SBE35RT-T1 versus pressure.

   [image]SBE35RT-T2 versus pressure.

   [image]T1-T2 versus pressure.

The 95% confidence limits for the mean low-gradient (values -0.002°C
\leq T1-T2 \leq 0.002°C) differences are ±0.00391°C for SBE35RT-T1,
±0.00387°C for SBE35RT-T2 and ±0.00157°C for T1-T2. The 95% confidence
limits for the deep temperature residuals (where pressure \geq
2000dbar) are ±0.00087°C for SBE35RT-T1, ±0.00099°C for SBE35RT-T2 and
±0.00087°C for T1-T2.

Minor complications impacted the temperature sensor data used for the
A22-2021 cruise.
   * Near-surface temperature gradients in the southern end of the
     survey were extremely sharp, occasionally causing SBE35RT
     readings to be questionable.

The resulting affected sections of data have been coded and documented
in the quality code APPENDIX.


Conductivity Analysis
---------------------

Laboratory calibrations of conductivity sensors were performed prior
to the cruise at the Sea-Bird Calibration Facility. Dates of
laboratory calibration are recorded on the underway sampling package
table and calibration documents are provided in the APPENDIX.

The pre-cruise laboratory calibration coefficients were used to
convert SBE4C frequencies to mS/cm conductivity values. Additional
shipboard calibrations were performed to correct sensor bias.
Corrections for both pressure and temperature sensors were finalized
before analyzing conductivity differences. Two independent metrics of
calibration accuracy were examined. At each bottle closure, the
primary and secondary conductivity were compared with each other. Each
sensor was also compared to conductivity calculated from check sample
salinities using CTD pressure and temperature.

The differences between primary and secondary temperature sensors were
used as filtering criteria to reduce the contamination of conductivity
comparisons by package wake. The coherence of this relationship is
shown in the following figure.

   [image]Coherence of conductivity differences as a function of
   temperature differences.

   [image]Corrected C_Bottle - C1 versus station.

   [image]Deep Corrected C_Bottle - C1 versus station (Pressure >=
   2000dbar).

   [image]Corrected C_Bottle - C2 versus station.

   [image]Deep Corrected C_Bottle - C2 versus station (Pressure >=
   2000dbar).

   [image]Corrected C1-C2 versus station.

   [image]Deep Corrected C1-C2 versus station (Pressure >= 2000dbar).

   [image]Corrected C_Bottle - C1 versus pressure.

   [image]Corrected C_Bottle - C2 versus pressure.

   [image]Corrected C1-C2 versus pressure.

A functioning SBE4C sensor typically exhibit a predictable modeled
response. Offsets for each C sensor were determined using C_Bottle -
C_CTD differences in a deeper pressure range (500 or more dbars).
After conductivity offsets were applied to all casts, response to
pressure, temperature and conductivity were examined for each
conductivity sensor. The response model is second-order with respect
to pressure, second-order with respect to temperature, and second-
order with respect to conductivity:

   C_{cor} = C + cp_2 P^2 + cp_1 P + ct_2 T^2 + ct_1 T + cc_2 C^2 +
   cc_1 C + \text{Offset}

Fit coefficients are shown in the following tables.


Primary conductivity (C1) coefficients.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Station      | cp_2         | cp_1         | ct_2         | ct_1         | cc_2         | cc_1         | c_0          |
|==============|==============|==============|==============|==============|==============|==============|==============|
| 901-29       | 2.2312e-10   | -1.7838e-6   | 0.0          | -3.7387e-4   | 0.0          | 0.0          | 1.4153e-3    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 30-73        | 2.9375e-10   | -2.7234e-6   | 0.0          | -5.1639e-4   | 0.0          | 0.0          | 3.1780e-3    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 74-90        | 3.0952e-11   | -7.2679e-7   | 0.0          | -2.3689e-4   | 0.0          | 0.0          | -1.1248e-3   |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+


Secondary conductivity (C2) coefficients.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Station      | cp_2         | cp_1         | ct_2         | ct_1         | cc_2         | cc_1         | c_0          |
|==============|==============|==============|==============|==============|==============|==============|==============|
| 901-29       | 1.6912e-10   | -1.3829e-6   | 0.0          | 0.0          | 0.0          | -3.2935e-4   | 1.3273e-2    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 30-73        | 1.7407e-10   | -1.6959e-6   | 0.0          | 0.0          | 0.0          | -5.1483e-4   | 2.0042e-2    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 74-90        | 5.4163e-11   | -9.0604e-7   | 0.0          | 0.0          | 0.0          | -2.0301e-4   | 8.8063e-3    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+

Salinity residuals after applying shipboard P/T/C corrections are
summarized in the following figures. Only CTD and bottle salinity data
with “acceptable” quality codes are included in the differences.
Quality codes and comments are published in the APPENDIX of this
report.

   [image]Salinity residuals versus station.

   [image]Deep Salinity residuals versus station (Pressure >=
   2000dbar).

   [image]Salinity residuals versus pressure.

The 95% confidence limits for the mean low-gradient (values -0.002 ºC
\leq T1-T2 \leq 0.002 ºC) differences are ±0.00512 mPSU for salinity-
C1SAL. The 95% confidence limits for the deep salinity residuals
(where pressure \geq 2000dbar) are ±0.00158 mPSU for salinity-C1SAL.

Minimal issues affected conductivity and calculated CTD salinities
during this cruise.
   * Bottle stops in halocline may have had insufficient stop time
     during some casts, leading to low-biased measurements.

The resulting affected sections of data have been coded and documented
in the quality code APPENDIX.


CTD Dissolved Oxygen (SBE43)
----------------------------

Laboratory calibrations of the dissolved oxygen sensors were performed
prior to the cruise at the SBE calibration facility. Dates of
laboratory calibration are recorded on the underway sampling package
table and calibration documents are provided in the APPENDIX.

The pre-cruise laboratory calibration coefficients were used to
convert SBE43 frequencies to µmol/kg oxygen values for acquisition
only. Additional shipboard fitting were performed to correct for the
sensors non-linear response. Corrections for pressure, temperature,
and conductivity sensors were finalized before analyzing dissolved
oxygen data. Corrections for hysteresis are applied following Sea-Bird
Application Note 64-3. The SBE43 sensor data were compared to
dissolved O_2 check samples taken at bottle stops by matching the
downcast CTD data to the upcast trip locations along isopycnal
surfaces. CTD dissolved O_2 was then calculated using Clark Cell MPOD
O_2 sensor response model for Beckman/SensorMedics and SBE43 dissolved
O_2 sensors. The residual differences of bottle check value versus CTD
dissolved O_2 values are minimized by optimizing the PMEL DO sensor
response model coefficients using the BFGS non-linear least-squares
fitting procedure.

The general form of the PMEL DO sensor response model equation for
Clark cells follows Brown and Morrison [Mill82] and Owens [Owen85].
Dissolved O_2 concentration is then calculated:

   O_2 = S_{oc} \cdot (V + V_{\textrm{off}} + \tau_{20} \cdot e^{(D_1
   \cdot p + D_2 \cdot (T - 20))} \cdot dV/dt) \cdot O_{sat} \cdot
   e^{T_{cor} \cdot T} \cdot e^{[(E \cdot p) / (273.15 + T)]}

Where:

* V is oxygen voltage (V)

* D_1 and D_2 are (fixed) SBE calibration coefficients

* T is corrected CTD temperature (°C)

* p is corrected CTD pressure (dbar)

* dV/dt is the time-derivative of voltage (V/s)

* O_sat is oxygen saturation

* S_oc, V_off, \tau_20, T_cor, and E are fit coefficients

All stations were fit together to get an initial coefficient estimate.
Stations were then fit individually to refine the coefficients as the
membrane does not deform the same way with each cast. If the fit of
the individual cast had worse resdiuals than the group, they were
reverted to the original group fit coefficients.


SBE43 group fit coefficients. Coefficients were further refined station-by-station.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+---------+--------------+---------------+-------------------------+---------------+--------------+
| Station | S_oc         | V_off         | \tau_20                 | T_cor         | E            |
|=========|==============|===============|=========================|===============|==============|
| 901-90  | 4.7574e-1    | -5.0079e-1    | 1.56                    | -3.1680e-4    | 3.754e-2     |
+---------+--------------+---------------+-------------------------+---------------+--------------+

CTD dissolved O_2 residuals are shown in the following figures O2
residuals versus station. through Deep O2 residuals versus station
(Pressure >= 2000dbar)..

   [image]O_2 residuals versus station.

   [image]Deep O_2 residuals versus station (Pressure >= 2000dbar).

   [image]O_2 residuals versus pressure.

The 95% confidence limits of 1.71 (µmol/kg) for all acceptable (flag
2) dissolved oxygen bottle data values and 1.52 (µmol/kg) for deep
dissolved oxygen values are only presented as general indicators of
the goodness of fit. CLIVAR GO-SHIP standards for CTD dissolved oxygen
data are < 1% accuracy against on board Winkler titrated dissolved O_2
lab measurements.

Minimal issues arose with the acquisition and processing of CTD
dissolved oxygen data.
   * Fitting routines were not behaving well for certain stations.
     SBE43 data are not reported but will be further investigated on
     land.


CTD Dissolved Oxygen (RINKO)
----------------------------

A two-point calibration was performed prior and after deployment on
the rosette. These calibrations produced sets of calibration
coefficients (G and H) to adjust factory calibration of dissolved
oxygen raw voltage. The calibrations also provided an assessment of
foil degradation over the course of the 90 stations. As per
manufacturer (JFE Advantech Co., Ltd.) recommendation, 100% saturation
points were obtained via bubbling ambient air in a stirred beaker of
tap water about 30 minutes, removing air stone, then submersing the
powered Rinko. Zero point calibrations also followed general
manufacturer recommendations, using a sodium sulfite solution (25g in
500mL deionized water). Dissolved oxygen raw voltage (DOout),
atmospheric pressure, and solution temperature were recorded for
calculation of new oxygen sensor coefficients (G and H).

Rinko temperature (factory coefficients) was used for pre-cruise
calibration. Generally, the Rinko III sensor appears to have performed
as expected with no major problems or sharp drift throughout the
deployment. An SBE 43 dissolved oxygen sensor was deployed
simultaneously. Both oxygen sensor data sets were analyzed and quality
controlled with Winkler bottle oxygen data. RinkoIII data used as
primary oxygen for all stations (1-90).

RINKO data was acquired, converted from volts to oxygen saturation,
and then multipled by the oxygen solubility to find values in µmol/kg.
The resulting data were then fitted using the equations developed by
[Uchida08]:

   [O_2] = (V_0 / V_c - 1) / K_{sv}

   K_{sv} = c_0 + c_1 T + c_2 T^2, \hspace{6pt} V_0 = 1 + d_0 T,
   \hspace{6pt} V_c = d_1 + d_2 V_r

where:

* T is temperature (ºC)

* V_r is raw voltage (V)

* V_0 is voltage at zero O_2 (V)

* c_0, c_1, c_2, d_0, d_1, d_2 are calibration coefficients

Oxygen is further corrected for pressure effects:

   [O_2]_c = [O_2] (1 + c_p P / 1000) ^ {1/3}

where:

* P is pressure (dbar)

* c_p is pressure compensation coefficient

Lastly, salinity corrections are applied [GarciaGordon1992]:

   [O_2]_{sc} = [O_2]_c \exp[{S (B_0 + B_1 T_S + B_2 T_S^2 + B_3
   T_S^3) + C_0 S^2}]

where:

* T_S is scaled temperature (T_S = ln[(298.15 – T)/(273.15 + T)])

* B_0, B_1, B_2, B_3, C_0 are solubility coefficients

All stations were fit together to get an initial coefficient estimate.
Stations were then fit in groups of similar profiles to get a further
refined estimate. Individual casts were then fit to remove the
noticeable time drift in coefficients If the fit of the individual
cast had worse resdiuals than the group, they were reverted to the
original group fit coefficients.


Rinko group fit coefficients. Coefficients were further refined station-by-station.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| Station      | c_0          | c_1          | c_2          | d_0          | d_1          | d_2          | c_p          |
|==============|==============|==============|==============|==============|==============|==============|==============|
| 901-29       | 1.8834       | 2.7106e-2    | 7.5022e-4    | 5.1571e-4    | -1.9373e-1   | 3.0792e-1    | 8.7822e-2    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 30-72        | 1.8612       | 2.9074e-2    | 9.2059e-4    | 2.4233e-3    | -1.9987e-1   | 3.1466e-1    | 9.7739e-2    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 73-90        | 1.8783       | 4.8992e-2    | 2.2758e-4    | 2.9361e-3    | -1.8483e-1   | 2.9822e-1    | 6.7778e-2    |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+

CTD dissolved O_2 residuals are shown in the following figures.

   [image]O_2 residuals versus station.

   [image]Deep O_2 residuals versus station (Pressure >= 2000dbar).

   [image]O_2 residuals versus pressure.

The 95% confidence limits of 1.27 (µmol/kg) for all acceptable (flag
2) dissolved oxygen bottle data values and 0.58 (µmol/kg) for deep
dissolved oxygen values are only presented as general indicators of
the goodness of fit. CLIVAR GO-SHIP standards for CTD dissolved oxygen
data are < 1% accuracy against on board Winkler titrated dissolved O_2
lab measurements.

No issues arose with the acquisition and processing of CTD dissolved
oxygen data.

[Mill82] Millard, R. C., Jr., “CTD calibration and data processing
         techniques at WHOI using the practical salinity scale,” Proc.
         Int. STD Conference and Workshop, p. 19, Mar. Tech. Soc., La
         Jolla, Ca. (1982).

[Owen85] Owens, W. B. and Millard, R. C., Jr., “A new algorithm for
         CTD oxygen calibration,” Journ. of Am. Meteorological Soc.,
         15, p. 621 (1985).

[Uchida08] Uchida, H., Kawano, T., Kaneko, I., Fukasawa, M. “In Situ
           Calibration of Optode-Based Oxygen Sensors,” J. Atmos.
           Oceanic Technol., 2271-2281, (2008)

[GarciaGordon1992] García, H. E., and L. I. Gordon, 1992: Oxygen
                   solubility in sea- water: Better fitting equations.
                   Limnol. Oceanogr., 37, 1307– 1312.


Salinity
========

PIs
   * Susan Becker (SIO)

   * James Swift (SIO)

Technicians
   * John Calderwood (SIO)

   * Caitlyn Webster (SIO)


Equipment and Techniques
------------------------

Two Guildline Autosals were on board and operational, SIO-owned 8400B
S/N 69-180, and UW-owned 8400B S/N 94-894. S/N 69-180 was used for all
salinity measurements during this cruise. The salinity analysis was
run in the ship’s Climate Controlled Chamber, a refrigerator port and
amidships between the Computer Lab and Bioanalytical Lab. The chamber
temperature varied between about 21 and 25 degrees Celcius around 3
times each hour, with an average (based on measuring temperatures of
items in the chamber) of about 23C.

Both instruments were serviced prior to the cruise by their respective
institutions and shipped to WHOI with other equipment in March. IAPSO
Standard Seawater Batch P-164 was used for all calibrations: K15
=0.99985, salinity 34.994, expiration 2023-03-23. A LabView program
developed by Carl Mattson was used for monitoring temperatures,
logging data and prompting the operator. Salinity analyses were
performed after samples had equilibrated to laboratory temperature of
23°C, usually 8 hours or more after collection. The salinometer was
standardized for each group of samples analyzed (normally 1 or 2
casts, up to 72 samples) using two bottles of standard seawater: one
at the beginning and one at the end of each set of measurements.

Between runs the water from the last standard was left in the cell.
For each calibration standard and sample reading, the salinometer cell
was initially flushed at least 2 times before a set of conductivity
ratio readings was recorded.


Sampling and Data Processing
----------------------------

The salinity samples were collected in 200 ml Kimax high-alumina
borosilicate bottles that had been rinsed at least three times with
sample water prior to filling. The bottles were sealed with plastic
insert thimbles and Nalgene screw caps. This assembly provides very
low container dissolution and sample evaporation. Prior to sample
collection, inserts were inspected for proper fit and loose inserts
replaced to insure an airtight seal. Laboratory temperature was also
monitored electronically throughout the cruise. PSS-78 salinity
[UNESCO1981] was calculated for each sample from the measured
conductivity ratios. The offset between the initial standard seawater
value and its reference value was applied to each sample. Then the
difference (if any) between the initial and final vials of standard
seawater was applied to each sample as a function of elapsed run time.
The corrected salinity data was then incorporated into the cruise
database.


Narrative
---------

No major problems were encountered during this cruise.

2975 total salinity samples were taken from a test cast (5 samples)
and 90 CTD casts (2970). Three sample bottles were broken during
sampling.

[UNESCO1981] UNESCO 1981. Background papers and supporting data on the
             Practical Salinity Scale, 1978. UNESCO Technical Papers
             in Marine Science, No. 37 144.


Nutrients
=========

Technicians
   * Susan Becker (SIO)

   * Alexandra Fine (AOML/CIMAS)


Summary of Analysis
-------------------

* 2977 samples from 90 CTD stations

* The cruise started with new pump tubes and they were changed once,
  before station 033.

* 2 sets of Primary/Secondary standards were made up over the course
  of the cruise.

* The cadmium column efficiency was checked periodically and ranged
  between 85%-100%.


Equipment and Techniques
------------------------

Nutrient analyses (phosphate, silicate, nitrate+nitrite, and nitrite)
were performed on a Seal Analytical continuous-flow AutoAnalyzer 3
(AA3). The methods used are described by Gordon et al [Gordon1992]
Hager et al. [Hager1972], and Atlas et al. [Atlas1971]. Details of
modification of analytical methods used in this cruise are also
compatible with the methods described in the nutrient section of the
updated GO-SHIP repeat hydrography manual (Becker et al., 2019,
[Becker 2019]_.


Nitrate/Nitrite Analysis
------------------------

A modification of the Armstrong et al. (1967) [Armstrong1967]
procedure was used for the analysis of nitrate and nitrite. For
nitrate analysis, a seawater sample was passed through a cadmium
column where the nitrate was reduced to nitrite. This nitrite was then
diazotized with sulfanilamide and coupled with
N-(1-naphthyl)-ethylenediamine to form a red dye. The sample was then
passed through a 10mm flowcell and absorbance measured at 520nm. The
procedure was the same for the nitrite analysis but without the
cadmium column.

**REAGENTS**

Sulfanilamide
   Dissolve 10g sulfamilamide in 1.2N HCl and bring to 1 liter volume.
   Add 2 drops of 40% surfynol 465/485 surfactant. Store at room
   temperature in a dark poly bottle.

   Note: 40% Surfynol 465/485 is 20% 465 plus 20% 485 in DIW.

N-(1-Naphthyl)-ethylenediamine dihydrochloride (N-1-N)
   Dissolve 1g N-1-N in DIW, bring to 1 liter volume. Add 2 drops 40%
   surfynol 465/485 surfactant. Store at room temperature in a dark
   poly bottle. Discard if the solution turns dark reddish brown.

Imidazole Buffer
   Dissolve 13.6g imidazole in ~3.8 liters DIW. Stir for at least 30
   minutes to completely dissolve. Add 60 ml of CuSO4 + NH4Cl mix (see
   below). Add 4 drops 40% Surfynol 465/485 surfactant. Let sit
   overnight before proceeding. Using a calibrated pH meter, adjust to
   pH of 7.83-7.85 with 10% (1.2N) HCl (about 10 ml of acid, depending
   on exact strength). Bring final solution to 4L with DIW. Store at
   room temperature.

NH4Cl + CuSO4 mix
   Dissolve 2g cupric sulfate in DIW, bring to 100 m1 volume (2%).
   Dissolve 250g ammonium chloride in DIW, bring to 1l liter volume.
   Add 5ml of 2% CuSO4 solution to this NH4Cl stock. This should last
   many months.


Phosphate Analysis
------------------

Ortho-Phosphate was analyzed using a modification of the Bernhardt and
Wilhelms (1967) [Bernhardt1967] method. Acidified ammonium molybdate
was added to a seawater sample to produce phosphomolybdic acid, which
was then reduced to phosphomolybdous acid (a blue compound) following
the addition of dihydrazine sulfate. The sample was passed through a
10mm flowcell and absorbance measured at 820nm.

**REAGENTS**

Ammonium Molybdate H2SO4 sol’n
   Pour 420 ml of DIW into a 2 liter Ehrlenmeyer flask or beaker,
   place this flask or beaker into an ice bath. SLOWLY add 330 ml of
   conc H2SO4. This solution gets VERY HOT!! Cool in the ice bath.
   Make up as much as necessary in the above proportions.

   Dissolve 27g ammonium molybdate in 250ml of DIW. Bring to 1 liter
   volume with the cooled sulfuric acid sol’n. Add 3 drops of 15% DDS
   surfactant. Store in a dark poly bottle.

Dihydrazine Sulfate
   Dissolve 6.4g dihydazine sulfate in DIW, bring to 1 liter volume
   and refrigerate.


Silicate Analysis
-----------------

Silicate was analyzed using the basic method of Armstrong et al.
(1967). Acidified ammonium molybdate was added to a seawater sample to
produce silicomolybdic acid which was then reduced to silicomolybdous
acid (a blue compound) following the addition of stannous chloride.
The sample was passed through a 10mm flowcell and measured at 660nm.

**REAGENTS**

Tartaric Acid
   Dissolve 200g tartaric acid in DW and bring to 1 liter volume.
   Store at room temperature in a poly bottle.

Ammonium Molybdate
   Dissolve 10.8g Ammonium Molybdate Tetrahydrate in 1000ml dilute
   H2SO4. (Dilute H2SO4 = 2.8ml conc H2SO4  or 6.4ml of H2SO4 diluted
   for PO4 moly per liter DW) (dissolve powder, then add H2SO4) Add
   3-5 drops 15% SDS surfactant per liter of solution.

Stannous Chloride
   stock: (as needed)

   Dissolve 40g of stannous chloride in 100 ml 5N HCl. Refrigerate in
   a poly bottle.

   NOTE: Minimize oxygen introduction by swirling rather than shaking
   the solution. Discard if a white solution (oxychloride) forms.

   working: (every 24 hours) Bring 5 ml of stannous chloride stock to
   200 ml final volume with 1.2N HCl. Make up daily - refrigerate when
   not in use in a dark poly bottle.


Sampling
--------

Nutrient samples were drawn into 30 ml polypropylene screw-capped
centrifuge tubes. The tubes and caps were cleaned with 10% HCl and
rinsed 2-3 times with sample before filling. Samples were analyzed
within 4 hours after sample collection, allowing sufficient time for
all samples to reach room temperature. The centrifuge tubes fit
directly onto the sampler.


Data Collection and Processing
------------------------------

Data collection and processing was done with the software provided
with the instrument from Seal Analytical (AACE). After each run, the
charts were reviewed for any problems during the run, any blank was
subtracted, and final concentrations (micro moles/liter) were
calculated, based on a linear curve fit. Once the run was reviewed and
concentrations calculated a text file was created. That text file was
reviewed for possible problems and then converted to another text file
with only sample identifiers and nutrient concentrations that was
merged with other bottle data.


Standards and Glassware Calibration
-----------------------------------

Primary standards for silicate (Na2SiF6), nitrate (KNO3), nitrite
(NaNO2), and phosphate (KH2PO4) were obtained from Johnson Matthey
Chemical Co. and/or Fisher Scientific. The supplier reports purities
of >98%, 99.999%, 97%, and 99.999 respectively.

All glass volumetric flasks and pipettes were gravimetrically
calibrated prior to the cruise. The primary standards were dried and
weighed out to 0.1mg prior to the cruise. The exact weight was noted
for future reference. When primary standards were made, the flask
volume at 20C, the weight of the powder, and the temperature of the
solution were used to buoyancy-correct the weight, calculate the exact
concentration of the solution, and determine how much of the primary
was needed for the desired concentrations of secondary standard. The
new standards were compared to the old before use.

All the reagent solutions, primary and secondary standards were made
with fresh distilled deionized water (DIW).

Standardizations were performed at the beginning of each group of
analyses with working standards prepared every 12-16 hours from a
secondary. Working standards were made up in low nutrient seawater
(LNSW). Two batches of LNSW were used on the cruise. The first batch
of LNSW was treated in the lab. The water was re-circulated for ~8
hours through a 0.2 micron filter, passed a UV lamp and through a
second 0.2 micron filter. The actual concentration of nutrients in
this water was empirically determined during the standardization
calculations.

The concentrations in micro-moles per liter of the working standards
used were:

+-----+-------+-------+-------+-------+
| -   | N+N   | PO_4  | SIL   | NO_2  |
|     | (uM)  | (uM)  | (uM)  | (uM)  |
|=====|=======|=======|=======|=======|
| 0   | 0.0   | 0.0   | 0.0   | 0.0   |
+-----+-------+-------+-------+-------+
| 3   | 15.50 | 1.2   | 60    | 0.50  |
+-----+-------+-------+-------+-------+
| 5   | 31.00 | 2.4   | 120   | 1.00  |
+-----+-------+-------+-------+-------+
| 7   | 46.50 | 3.6   | 180   | 1.50  |
+-----+-------+-------+-------+-------+


Quality Control
---------------

All final data was reported in micro-moles/kg. NO_3, PO_4, and NO_2
were reported to two decimals places and SIL to one. Accuracy is based
on the quality of the standards the levels are:

+-------+-----------------------------+
| NO_3  | 0.05 µM (micro moles/Liter) |
+-------+-----------------------------+
| PO_4  | 0.004 µM                    |
+-------+-----------------------------+
| SIL   | 2-4 µM                      |
+-------+-----------------------------+
| NO_2  | 0.05 µM                     |
+-------+-----------------------------+

The deep check sample that is normally run was discontinued due to
issues with cadmium column efficiency on A20.  It is thought the
mercuric chloride may have been contributing to the loss of column
efficiency.

Reference materials for nutrients in seawater (RMNS) were used as a
check sample run with every station. The RMNS preparation,
verification, and suggested protocol for use of the material are
described by [Aoyama2006] [Aoyama2007], [Aoyama2008], Sato [Sato2010]
and Becker et al. [Becker 2019]. RMNS batch C0 was used on this
cruise, with each bottle being used for all runs in one day before
being discarded and a new one opened. Data are tabulated below.

+-----------+---------------+---------+---------------+
| Parameter | Concentration | stddev  | assigned conc |
|===========|===============|=========|===============|
| -         | (µmol/kg)     | -       | (µmol/kg)     |
+-----------+---------------+---------+---------------+
| NO_3      | 15.86         | 0.02    | 15.86         |
+-----------+---------------+---------+---------------+
| PO_4      | 1.17          | 0.005   | 1.177         |
+-----------+---------------+---------+---------------+
| Sil       | 34.7          | 0.12    | 34.72         |
+-----------+---------------+---------+---------------+
| NO_2      | 0.04          | 0.005   | 0.04          |
+-----------+---------------+---------+---------------+


Analytical Problems
-------------------

There were issues with the cadmium column efficiency on A20. The exact
issue was never clearly identified but it appears to have been a
combination of buffer that was not stable which affected the
efficiency and life span of the cadmium reduction columns. The values
of the reference material and the were used to in addition to the
periodic column efficiency checks to monitor data quality. Adjustments
based on the values obtained for the references material were made as
necessary. The adjusted data for affected stations was compared to
adjacent stations and historical data during the final QC checks.

[Armstrong1967] Armstrong, F.A.J., Stearns, C.A., and Strickland,
                J.D.H., “The measurement of upwelling and subsequent
                biological processes by means of the Technicon
                Autoanalyzer and associated equipment,” Deep-Sea
                Research, 14, pp.381-389 (1967).

[Atlas1971] Atlas, E.L., Hager, S.W., Gordon, L.I., and Park, P.K., “A
            Practical Manual for Use of the Technicon AutoAnalyzer in
            Seawater Nutrient Analyses Revised,” Technical Report 215,
            Reference 71-22, p.49, Oregon State University,
            Department of Oceanography (1971).

[Aoyama2006] Aoyama, M., 2006: 2003 Intercomparison Exercise for
             Reference Material for Nutrients in Seawater in a
             Seawater Matrix, Technical Reports of the Meteorological
             Research Institute No.50, 91pp, Tsukuba, Japan.

[Aoyama2007] Aoyama, M., Susan B., Minhan, D., Hideshi, D., Louis, I.
             G., Kasai, H., Roger, K., Nurit, K., Doug, M., Murata,
             A., Nagai, N., Ogawa, H., Ota, H., Saito, H., Saito, K.,
             Shimizu, T., Takano, H., Tsuda, A., Yokouchi, K., and
             Agnes, Y. 2007. Recent Comparability of Oceanographic
             Nutrients Data: Results of a 2003 Intercomparison
             Exercise Using Reference Materials. Analytical Sciences,
             23: 1151-1154.

[Aoyama2008] Aoyama M., J. Barwell-Clarke, S. Becker, M. Blum, Braga
             E. S., S. C. Coverly,E. Czobik, I. Dahllof, M. H. Dai, G.
             O. Donnell, C. Engelke, G. C. Gong, Gi-Hoon Hong, D. J.
             Hydes, M. M. Jin, H. Kasai, R. Kerouel, Y. Kiyomono, M.
             Knockaert, N. Kress, K. A. Krogslund, M. Kumagai, S.
             Leterme, Yarong Li, S. Masuda, T. Miyao, T. Moutin, A.
             Murata, N. Nagai, G.Nausch, M. K. Ngirchechol, A. Nybakk,
             H. Ogawa, J. van Ooijen, H. Ota, J. M. Pan, C. Payne, O.
             Pierre-Duplessix, M. Pujo-Pay, T. Raabe, K. Saito, K.
             Sato, C. Schmidt, M. Schuett, T. M. Shammon, J. Sun, T.
             Tanhua, L. White, E.M.S. Woodward, P. Worsfold, P. Yeats,
             T. Yoshimura, A.Youenou, J. Z. Zhang, 2008: 2006
             Intercomparison Exercise for Reference Material for
             Nutrients in Seawater in a Seawater Matrix, Technical
             Reports of the Meteorological Research Institute No. 58,
             104pp.

[Bernhardt1967] Bernhardt, H., and  Wilhelms, A., “The continuous
                determination of low level iron, soluble phosphate and
                total phosphate with the AutoAnalyzer,” Technicon
                Symposia, I,pp.385-389 (1967).

[Gordon1992] Gordon, L.I., Jennings, J.C., Ross, A.A., Krest, J.M., “A
             suggested Protocol for Continuous Flow Automated Analysis
             of Seawater Nutrients in the WOCE Hydrographic Program
             and the Joint Global Ocean Fluxes Study,” Grp. Tech Rpt
             92-1, OSU College of Oceanography Descr. Chem Oc. (1992).

[Hager1972] Hager, S.W.,  Atlas, E.L., Gordon L.I., Mantyla, A.W., and
            Park, P.K., ” A comparison at sea of manual and
            autoanalyzer analyses of phosphate, nitrate, and silicate
            ,” Limnology and Oceanography, 17,pp.931-937 (1972).

[Kerouel1997] Kerouel, R., Aminot, A., “Fluorometric determination of
              ammonia in sea and estuarine waters by direct segmented
              flow analysis.” Marine Chemistry, vol 57, no. 3-4, pp.
              265-275, July 1997.

[Sato2010] Sato, K., Aoyama, M., Becker, S., 2010. RMNS as Calibration
           Standard Solution to Keep Comparability for Several Cruises
           in the World Ocean in 2000s. In: Aoyama, M., Dickson, A.G.,
           Hydes, D.J., Murata, A., Oh, J.R., Roose, P., Woodward,
           E.M.S., (Eds.), Comparability of nutrients in the world’s
           ocean. Tsukuba, JAPAN: MOTHER TANK, pp 43-56.


Oxygen Analysis
===============

PIs
   * Susan Becker (SIO)

   * James Swift (SIO)

Technicians
   * Andrew Barna (SIO)

   * Robert “Ben” Freiberger (SIO)


Equipment and Techniques
------------------------

Dissolved oxygen analyses were performed with an SIO/ODF-designed
automated oxygen titrator using photometric end-point detection based
on the absorption of 365nm wavelength ultra-violet light. The
titration of the samples and the data logging were controlled by PC
LabView software. Thiosulfate was dispensed by a Dosimat 665 buret
driver fitted with a 1.0 ml burette.

ODF used a whole-bottle modified-Winkler titration following the
technique of Carpenter [Carpenter1965] with modifications by
[Culberson1991] but with higher concentrations of potassium iodate
standard (~0.012 N), and thiosulfate solution (~55 g/L).

Pre-made liquid potassium iodate standards and reagent/distilled water
blanks were run every day (approximately every 3-4 stations), with
samples analysed within 24 hours of the last standard.


Sampling and Data Processing
----------------------------

A total of 2969 oxygen measurements were made, all of which were
niskin samples. There are no underway samples. Niskin samples were
collected soon after the rosette was secured on deck, either from
fresh niskins or immediately following CFC sampling.

Nominal 125 mL volume-calibrated biological oxygen demand (BOD) flasks
were rinsed 3 times with minimal agitation using a silicone draw tube,
then filled and allowed to overflow for at least 3 flask volumes,
ensuring no bubbles remained. Pickling reagents MnCl2 and NaI/NaOH (1
mL of each) were added via bottle-top dispensers to fix samples before
stoppering. Flasks were shaken twice (10-12 inversions) to assure
thorough dispersion of the precipitate - once immediately after
drawing and then again after 30-60 minutes.

Sample draw temperatures, measured with an electronic resistance
temperature detector (RTD) embedded in the draw tube, were used to
calculate umol/kg concentrations, and as a diagnostic check of bottle
integrity.

Niskin samples were analysed within 2-12 hours of collection, and the
data incorporated into the cruise database. Underway samples were
analysed within 96 hours of collection.

Thiosulfate normalities were calculated for each standardisation and
corrected to 20°C. The 20°C thiosulfate normalities and blanks were
plotted versus time and were reviewed for possible problems, and were
subsequently determined to be stable enough that no smoothing was
required.


Volumetric Calibration
----------------------

Oxygen flask volumes were determined gravimetrically with degassed
deionised water to determine flask volumes at ODF’s chemistry
laboratory. This is done once before using flasks for the first time
and periodically thereafter when a suspect volume is detected. The 10
mL Dosimat buret used to dispense standard iodate solution was
calibrated using the same method.


Standards
---------

Liquid potassium iodate standards were prepared in 6 L batches and
bottled in sterile glass bottles at ODF’s chemistry laboratory prior
to the expedition. The normality of the liquid standard was determined
by calculation from weight. The standard was supplied by Alfa Aesar
and has a reported purity of 99.4-100.4%. All other reagents were
“reagent grade” and were tested for levels of oxidising and reducing
impurities prior to use.


Narrative
---------

The analytical rig remained set up from the just completed 2021
occupation of A20. This included all the reagents, though more NaI/OH
and MnCl2 were made while in port.

The thiosulfate stability was considered in 4 batches and showed
remarkable stability throughout the entire cruise. No trends were
observed or corrected for.

There was a freezing concern regarding the liquid reagents shipped to
WHOI prior to the start of A20. To verify that our standards were
good, some OSIL KIO3 standard was shipped to the US Virgin Islands to
load during the port call. These standards were all run during the
transit around Puerto Rico (between stations 29 and 30). All the ODF
standards agreed with each other, the OSIL standards were
inconclusive. Though perhaps the lesson learned was that the lead
analyst lacked sufficient skill with hand pipettes to use them.

No data updates are expected.

   [image]Bottle oxygen data gridded on isopycnals.

[Carpenter1965] Carpenter, J. H., “The Chesapeake Bay Institute
                technique for the Winkler dissolved oxygen method,”
                Limnology and Oceanography, 10, pp. 141-143 (1965).

[Culberson1991] Culberson, C. H., Knapp, G., Stalcup, M., Williams, R.
                T., and Zemlyak, F., “A comparison of methods for the
                deter mination of dissolved oxygen in seawater,” Repor
                t WHPO 91-2, WOCE Hydrographic Programme Office (Aug
                1991).


Total Alkalinity
================

PIs
   * Andrew G. Dickson (SIO)

   * Frank J. Millero (RSMAS)

Technicians
   * Carmen Rodriguez (RSMAS)

   * Daniela Nestory (SIO)


Total Alkalinity
----------------

The total alkalinity of sea water is defined as the number of moles of
hydrogen ion equivalent to the excess of proton acceptors (bases
formed from weak acids with a dissociation constant K < 10E-4.5 at
25°C and zero ionic strength) over proton donors (acids with K >
10E-4.5) in 1 kilogram of sample.


Total Alkalinity Measurement System
-----------------------------------

*Sample Delivery System:*

Samples are dispensed using a Sample Delivery System (SDS) which has
been calibrated for volume in the lab prior to the cruise. Its volume
is confirmed immediately before use at sea to ensure a consistent
volume will be delivered for each sample. The SDS consists of a
volumetric pipette, various relay valves, an air pump, and is
controlled by a program in LabVIEW 2012.

Before attaching a sample bottle to the SDS, the volumetric pipette is
cleared of any residual solution. The pipette is then rinsed and
filled with the sample. The sample overflows and time is allowed for
the sample temperature to equilibrate.

The sample bottle temperature is measured using a DirecTemp thermistor
probe inserted into the sample bottle and the volumetric pipette
temperature is measured using a DirecTemp surface probe placed
directly on the pipette. These temperature measurements, along with
the bottle salinity, are used to convert the sample volume to mass for
analysis.

Samples are delivered into a 250-mL water-jacketed open cell for
titration analysis. While one sample is undergoing titration, a second
sample is prepared with the SDS and equilibrated to 20°C for analysis.

*Open-Cell Titration:*

The total alkalinity is measured through an open-cell titration with a
dilute hydrochloric acid titrant of known concentration. A Metrohm 876
Dosimat Plus is used for all standardized hydrochloric acid additions.

An initial aliquot of approximately 2.3-2.4 mL of standardized
hydrochloric acid (~0.1M HCl in ~0.6M NaCl solution) is first
delivered and the sample is stirred for 5 minutes while air is bubbled
into at a rate of 200 scc/m to remove any liberated carbon dioxide
gas.

After equilibration, ~19 aliquots of 0.035 ml are added. Between the
pH range of 3.5 to 3.0, the progress of the titration is monitored
using a pH glass electrode/reference electrode cell, and the total
alkalinity is computed from the titrant volume and e.m.f. measurements
using a non-linear least-squares approach (Dickson, 2007).

A Thermo Scientific Isotemp water bath is connected to the water-
jacketed open cell to maintain a cell temperature of approximately
20oC. An Agilent 34970A Data Acquisition/Switch Unit with a 34901A
multiplexer is used to read the voltage measurements from the
electrode and monitor the temperatures from the sample, acid, and
room.

The calculations for this procedure are performed automatically using
LabVIEW 2012.


Sample Collection
-----------------

Alkalinity samples are drawn using silicone tubing connected to the
Niskin bottles and collected into 250 mL Pyrex bottles. The sample
bottles and Teflon-sleeved glass stoppers were rinsed at least twice
before the final filling. A headspace of approximately 3 mL was
removed and 0.05 mL of saturated mercuric chloride solution was added
to each sample for preservation. The samples were equilibrated prior
to analysis at approximately 20°C using a Thermo Scientific Isotemp
water bath.

Samples for total alkalinity were taken at all stations during A22
(1-90). Except for a few instances, alkalinity samples were collected
from each niskin where DIC and pH were collected, to over-characterize
the CO2 system. The typical sample scheme of full collection on even-
numbered stations (36 niskin bottles) and partial collection (~8-20
bottles) on odd-numbered stations was followed.

In order to evaluate the reproducibility of the alkalinity system,
duplicate samples (two separate alkalinity bottles) were collected at
a minimum of 10% of total samples. For instance, when all 36 niskins
were sampled, 3 duplicate samples were collected for alkalinity. When
alkalinity sampled a partial cast, one or two duplicate samples were
collected.


Problems and Troubleshooting
----------------------------

There were a few issues encountered at the start of the cruise which
delayed sample processing but did not impede sample intake. It was
determined that the SDS_A system, which had been used on Leg 1 (A20),
was leaking and further use would be problematic for this leg. The
spare system (SDS_B) was swapped in and extra time was needed to
confirm the accuracy and stability of the replacement SDS. Surplus
alkalinity bottles were available to stockpile samples so productivity
was not impeded. Also at the start of the cruise, an error in the
Labview program’s file creation resulted in configuration equations
being omitted which had to be reinput by hand initially. A typo in the
input equations was soon discovered and corrected.

The SDS system occasionally freezes at different points in the
procedure. However the technicians were alert to this issue and were
able to save most samples when this occurred.

Although the temperature in the lab was very stable for the majority
of the cruise, just before entering the Gulf Stream (starting at
station 71), the room temperature dropped by approximately 2oC. The
acid temperature dropped as well, causing errors in the calculations.
The engineers of the R/V TG Thompson worked to increase and stabilize
the room temperature. The cool climate continued for a couple of days,
so time was spent to combat temperature instability. Samples were not
run when the appropriate range in temperature could not be achieved.


Quality Control
---------------

Certified Reference Material (CRMs) and duplicate samples (two bottles
collected from one niskin) were used to quality check the functioning
of the total alkalinity system throughout the cruise.

Dickson laboratory Certified Reference Material (CRM) Batches 178 and
192 were used to determine the accuracy of the total alkalinity
analyses. The total alkalinity certified value for these batches are:

* Batch 178: 2216.53 ± 0.61 µmol/kg (132; 75)

* Batch 192 2213.70 ± 0.53 µmol/kg (132; 67)

The cited uncertainties represent the standard deviation.

Figures in parentheses are the number of analyses made (total number
of analyses; number of separate bottles analyzed).

A CRM sample was analyzed at a minimum frequency of once per every 20
runs, but more often once per every 15 runs. Because total alkalinity
is not affected by gas-exchange, brand new CRM bottles were reserved
for pH and DIC analysis. These pre-opened bottles were subsequently
used for alkalinity analysis. 264 reference material samples were
analyzed on A22.

The average measured total alkalinity value for each batch is:

* Batch 178: 2217.97 ± 1.99 µmol kg-1 (n = 132)

* Batch 192: 2214.40 ± 1.80 µmol kg-1 (n = 132)

Duplicate samples were also used to check the reproducibility of the
system. The absolute value of the mean offset between duplicate
samples and the standard deviation are given below. Mean duplicate
sample offset: 1.35 ± 1.03 µmol kg-1 (n = 161)

1884 total alkalinity values were submitted for A22.

Further dilution corrections need to be applied to this data back
onshore, therefore, this data is to be considered preliminary.


Dissolved Inorganic Carbon (DIC)
================================

PI’s
   * Rik Wanninkhof (NOAA/AOML)

   * Richard A. Feely (NOAA/PMEL)

Technicians
   * Charles Featherstone (NOAA/AOML)

   * Andrew Collins (NOAA/PMEL)


Sample Collection
-----------------

Samples for DIC measurements were drawn (according to procedures
outlined in the PICES Publication, *Guide to Best Practices for Ocean
CO2 Measurements* [Dickson2007]) from Niskin bottles into 294 ml
borosilicate glass bottles using silicone tubing. The flasks were
rinsed once and filled from the bottom with care not to entrain any
bubbles, overflowing by at least one-half volume. The sample tube was
pinched off and withdrawn, creating a 6 ml headspace, followed by 0.12
ml of saturated HgCl_2 solution which was added as a preservative. The
sample bottles were then sealed with glass stoppers lightly covered
with Apiezon-L grease and were stored at room temperature for a
maximum of 12 hours.


Equipment
---------

The analysis was done by coulometry with two analytical systems (AOML
3 and AOML 4) used simultaneously on the cruise. Each system consisted
of a coulometer (CM5017 UIC Inc) coupled with a Dissolved Inorganic
Carbon Extractor (DICE). The DICE system was developed by Esa Peltola
and Denis Pierrot of NOAA/AOML and Dana Greeley of NOAA/PMEL to
modernize a carbon extractor called SOMMA ([Johnson1985],
[Johnson1987], [Johnson1993], [Johnson1992], [Johnson1999]).

The two DICE systems (AOML 3 and AOML 4) were set up in a seagoing
container modified for use as a shipboard laboratory on the aft main
working deck of the R/V Thomas G Thompson.


DIC Analysis
------------

In coulometric analysis of DIC, all carbonate species are converted to
CO_2 (gas) by addition of excess hydrogen ion (acid) to the seawater
sample, and the evolved CO_2 gas is swept into the titration cell of
the coulometer with pure air or compressed nitrogen, where it reacts
quantitatively with a proprietary reagent based on ethanolamine to
generate hydrogen ions. In this process, the solution changes from
blue to colorless, triggering a current through the cell and causing
coulometrical generation of OH^- ions at the anode. The OH^- ions
react with the H^+ and the solution turns blue again. A beam of light
is shone through the solution, and a photometric detector at the
opposite side of the cell senses the change in transmission. Once the
percent transmission reaches its original value, the coulometric
titration is stopped, and the amount of CO_2 that enters the cell is
determined by integrating the total change during the titration.


DIC Calculation
---------------

Calculation of the amount of CO2 injected was according to the CO2
handbook [DOE1994]. The concentration of CO2 ([CO2]) in the samples
was determined according to:

   [\text{CO}_2] = \text{Cal. Factor} * \frac{(\text{Counts} -
   \text{Blank} * \text{Run Time}) * K
   \mu\text{mol}/\text{count}}{\text{pipette volume} * \text{density
   of sample}}

where Cal. Factor is the calibration factor, Counts is the instrument
reading at the end of the analysis, Blank is the counts/minute
determined from blank runs performed at least once for each cell
solution, Run Time is the length of coulometric titration (in
minutes), and K is the conversion factor from counts to micromoles.

The instrument has a salinity sensor, but all DIC values were
recalculated to a molar weight (µmol/kg) using density obtained from
the CTD’s salinity. The DIC values were corrected for dilution due to
the addition of 0.12 ml of saturated HgCl_2 used for sample
preservation. The total water volume of the sample bottles was 294 ml
(calibrated by Esa Peltola, AOML). The correction factor used for
dilution was 1.00041. A correction was also applied for the offset
from the CRM. This additive correction was applied for each cell using
the CRM value obtained at the beginning of the cell. The average
correction was 1.51 µmol/kg for AOML 3 and 1.06 µmol/kg for AOML 4.

The coulometer cell solution was replaced after 24-28 mg of carbon was
titrated, typically after 9-12 hours of continuous use. The blanks
ranged from 12-55.


Calibration, Accuracy, and Precision
------------------------------------

The stability of each coulometer cell solution was confirmed three
different ways.

1. Gas loops were run at the beginning of each cell

2. CRM’s supplied by Dr. A. Dickson of SIO, were analyzed at the
   beginning of the cell before sample analysis.

3. Duplicate samples from the same niskin, were measured near the
   beginning; middle and end of each cell.

Each coulometer was calibrated by injecting aliquots of pure CO_2
(99.999%) by means of an 8-port valve [Wilke1993] outfitted with two
calibrated sample loops of different sizes (~1ml and ~2ml). The
instruments were each separately calibrated at the beginning of each
cell with a minimum of two sets of these gas loop injections.

The accuracy of the DICE measurement is determined with the use of
standards (Certified Reference Materials (CRMs), consisting of
filtered and UV irradiated seawater) supplied by Dr. A. Dickson of
Scripps Institution of Oceanography (SIO). The CRM accuracy is
determined manometrically on land in San Diego and the DIC data
reported to the data base have been corrected to this batch 178 CRM
value. The CRM certified value for this batch is 1952.65 µmol/kg.

The precision of the two DICE systems can be demonstrated via the
replicate samples. Approximately 10% of the niskins sampled were
duplicates taken as a check of our precision. These replicate samples
were interspersed throughout the station analysis for quality
assurance and integrity of the coulometer cell solutions. The average
absolute difference of these replicates was 1.34 (AOML 3) and 1.49
(AOML 4) µmol/kg - No major systematic differences between the
replicates were observed.

The pipette volume was determined by taking aliquots of distilled
water from volumes at known temperatures. The weights with the
appropriate densities were used to determine the volume of the
pipettes.

Calibration data during this cruise:

+---------+---------------------+------------+-----------------+-----------+----------------------+
| UNIT    | Ave Gas Cal Factor  | Pipette    | Ave CRM         | Std Dev   | Ave Difference Dupes |
|=========|=====================|============|=================|===========|======================|
| AOML3   | 1.00390             | 27.990 ml  | 1953.24, N = 43 | 1.14      | 1.34                 |
+---------+---------------------+------------+-----------------+-----------+----------------------+
| AOML4   | 1.00313             | 29.387 ml  | 1952.20, N = 41 | 1.25      | 1.49                 |
+---------+---------------------+------------+-----------------+-----------+----------------------+


Instrument Repairs
------------------

AOML 3 had a relay switch failure before Station 41. The relay switch
and micro acid pump were replaced and the instrument functioned well
for the rest of the cruise. The pipette was not filling properly
before Station 54. Valve 13 was found to be defective and replaced
which corrected the filling of the pipette.  AOML 3 functioned well
for the remainder of the cruise.


Summary
-------

The overall performance of the analytical equipment was good during
the cruise. Including the duplicates, a total of 2208 samples were
analyzed from 90 CTD casts for dissolved inorganic carbon (DIC), which
equates to a DIC value for 68% of the niskins tripped. The DIC data
reported to the database directly from the ship are to be considered
preliminary until a more thorough quality assurance can be completed
shore side.

[DOE1994] DOE (U.S. Department of Energy). (1994). *Handbook of
          Methods for the Analysis of the Various Parameters of the
          Carbon Dioxide System in Seawater*. Version 2.0.
          ORNL/CDIAC-74. Ed. A. G. Dickson and C. Goyet. Carbon
          Dioxide Information Analysis Center, Oak Ridge National
          Laboratory, Oak Ridge, Tenn.

[Dickson2007] Dickson, A.G., Sabine, C.L. and Christian, J.R. (Eds.),
              (2007): *Guide to Best Practices for Ocean CO2
              Measurements*. PICES Special Publication 3, 191 pp.

[Feely1998] Feely, R.A., R. Wanninkhof, H.B. Milburn, C.E. Cosca, M.
            Stapp, and P.P. Murphy (1998): *“A new automated underway
            system for making high precision pCO2 measurements aboard
            research ships.”* Anal. Chim. Acta, 377, 185-191.

[Johnson1985] Johnson, K.M., A.E. King, and J. McN. Sieburth (1985):
              *“Coulometric DIC analyses for marine studies: An
              introduction.”* Mar. Chem., 16, 61-82.

[Johnson1987] Johnson, K.M., P.J. Williams, L. Brandstrom, and J. McN.
              Sieburth (1987): *“Coulometric total carbon analysis for
              marine studies: Automation and calibration.”* Mar.
              Chem., 21, 117-133.

[Johnson1992] Johnson, K.M. (1992): Operator’s manual: *“Single
              operator multiparameter metabolic analyzer (SOMMA) for
              total carbon dioxide (CT) with coulometric detection.”*
              Brookhaven National Laboratory, Brookhaven, N.Y., 70 pp.

[Johnson1993] Johnson, K.M., K.D. Wills, D.B. Butler, W.K. Johnson,
              and C.S. Wong (1993): *“Coulometric total carbon dioxide
              analysis for marine studies: Maximizing the performance
              of an automated continuous gas extraction system and
              coulometric detector.”* Mar. Chem., 44, 167-189.

[Johnson1999] Johnson, K.M., Körtzinger, A.; Mintrop, L.; Duinker,
              J.C.; and Wallace, D.W.R. (1999). *Coulometric total
              carbon dioxide analysis for marine studies: Measurement
              and interna consistency of underway surface TCO2
              concentrations.* Marine Chemistry 67:123–44.

[Lewis1998] Lewis, E. and D. W. R. Wallace (1998) Program developed
            for CO2 system calculations. Oak Ridge, Oak Ridge National
            Laboratory. http://cdiac.ornl.gov/oceans/co2rprt.html

[Wilke1993] Wilke, R.J., D.W.R. Wallace, and K.M. Johnson (1993):
            “Water-based gravimetric method for the determination of
            gas loop volume.” Anal. Chem. 65, 2403-2406


Discrete pH Analyses (Total Scale)
==================================

PI
   * Dr. Andrew Dickson (SIO)

   * Dr. Frank Millero (RSMAS)

Technicians
   * Sidney Wayne (HPU)

   * Albert Ortiz (RSMAS)


Sampling
--------

Samples were collected in 250 mL Pyrex glass bottles and sealed using
grey butyl rubber stoppers held in place by aluminum-crimped caps.
Each bottle was rinsed two times and allowed to overflow by one half
additional bottle volume. Prior to sealing, each sample was given a 1%
headspace and poisoned with 0.02% of the sample volume of saturated
mercuric chloride (HgCl_2). Samples were collected only from Niskin
bottles that were also being sampled for both total alkalinity and
dissolved inorganic carbon in order to completely characterize the
carbon system. Additionally, duplicate samples were collected from all
stations for quality control purposes.


Analysis
--------

pH was measured spectrophotometrically on the total hydrogen scale
using an Agilent 8453 spectrophotometer and in accordance with the
methods outlined by Carter et al, 2013. [Carter2013]. A Kloehn V6
syringe pump was used to autonomously fill, mix, and dispense sample
through the custom 10cm flow-through jacketed cell. A Thermo Fisher
Isotemp recirculating water bath was used to maintain the cell
temperature at 25.0°C during analyses, and a YSI 4600 precision
thermometer and probe were used to monitor and record the temperature
of each sample during the spectrophotometric measurements. Purified
meta-cresol purple (mCP) was the indicator used to measure the
absorbance of light measured at two different wavelengths (434 nm, 578
nm) corresponding to the maximum absorbance peaks for the acidic and
basic forms of the indicator dye. A baseline absorbance was also
measured and subtracted from these wavelengths. The baseline
absorbance was determined by averaging the absorbances from 725-735nm.
The ratio of the absorbances was then used to calculate pH on the
total scale using the equations outlined in Liu et al., 2011
[Liu2011]. The salinity data used was obtained from the salinity
analysis conducted on board.


Reagents
--------

The mCP indicator dye was made up to a concentration of approximately
2.0mM and a total ionic strength of 0.7 M. A total of two batches were
used during A22. The pHs of these batches were adjusted with 0.1 mol
kg^-1 solutions of HCl and NaOH (in 0.6 mol kg^-1 NaCl background) to
approximately 7.80, measured with a pH meter calibrated with NBS
buffers. The indicator was obtained from Dr. Robert Byrne at the
University of Southern Florida and was purified using the flash
chromatography technique described by Patsavas et al., 2013.
[Patsavas2013].


Data Processing
---------------

An indicator dye is itself an acid-base system that can change the pH
of the seawater to which it is added. Therefore it is important to
estimate and correct for this perturbation to the seawater’s pH for
each batch of dye used during the cruise. To determine this
correction, multiple bottles from each station were measured twice,
once with a single addition of indicator dye and once with a double
addition of indicator dye. The measured absorbance ratio (R) and an
isosbestic absorbance (A_{\text{iso}}) were determined for each
measurement, where:

   R = \frac{A_{578} - A_{\text{base}}}{A_{434} - A_{\text{base}}}

and

   A_{\text{iso}} = A_{488} - A_{\text{base}}

The change in R for a given change in A_{\text{iso}}, \Delta R/\Delta
A_{\text{iso}}, was then plotted against the measured R-value for the
normal amount of dye and fitted with a linear regression. From this
fit the slope and y-intercept (b and a respectively) are determined
by:

   \Delta R/\Delta A_{\text{iso}} = bR + a

From this the corrected ratio (R') corresponding to the measured
absorbance ratio if no indicator dye were present can be determined
by:

   R' = R - A_{\text{iso}} (bR + a)


Problems and Troubleshooting
----------------------------

During the beginning of the cruise, the sample cell was broken due to
stress on the sample inlet glass tubes, but the lead tech was able to
rig the cell to remain operable.


Standardization/Results
-----------------------

The precision of the data was assessed from measurements of duplicate
analyses, replicate analyses (two successive measurements on one
bottle), and certified reference material (CRM) Batch 192 (provided by
Dr. Andrew Dickson, UCSD). two or three duplicates and one or two
replicate measurements were performed on every station when at least
twenty-four Niskins were sampled. If less than twenty-four Niskins
were sampled, only one or two duplicates and one replicate measurement
were performed. CRMs were measured at the beginning and ending of each
day.

The precision statistics for A22 are:

+----------------------------+--------------------------+
| Duplicate precision        | ± 0.0009 (n=190)         |
+----------------------------+--------------------------+
| Replicate precision        | ± 0.0010 (n=104)         |
+----------------------------+--------------------------+
| B192                       | 7.7493 ± 0.0016 (n=47)   |
+----------------------------+--------------------------+
| B192 within-bottle SD      | ± 0.0010 (n=47)          |
+----------------------------+--------------------------+

2001 pH values were submitted for A22. Additional corrections will
need to be performed and these data should be considered preliminary
until a more thorough analysis of the data can take place on shore.

[Carter2013] Carter, B.R., Radich, J.A., Doyle, H.L., and Dickson,
             A.G., “An Automated Spectrometric System for Discrete and
             Underway Seawater pH Measurements,” Limnology and
             Oceanography: Methods, 2013.

[Liu2011] Liu, X., Patsavas, M.C., Byrne R.H., “Purification and
          Characterization of meta Cresol Purple for
          Spectrophotometric Seawater pH Measurements,” Environmental
          Science and Technology, 2011.

[Patsavas2013] Patsavas, M.C., Byrne, R.H.,  and Liu X. “Purification
               of meta-cresol purple and cresol red by flash
               chromatography: Procedures for ensuring accurate
               spectrophotometric seawater pH measurements,” Marine
               Chemistry, 2013.


CFC, SF_6, and N_2O
===================

PIs
   * Mark J. Warner (UW)

Analysts
   * Mark J. Warner (UW)

   * Bonnie X. Chang (UW)

   * Lillian Henderson (RSMAS)

Warning:

  Note that N_2O measurements are a Level 3 measurement. The
  concentrations were measured on the same water samples collected for
  the Level 1 CFC/SF_6 measurements. The N_2O analysis is still under
  development. Please contact the PI for any use of these data.

Samples for the analysis of dissolved CFC-11, CFC-12, SF_6, and N_2O
were collected from approximately 1417 of the Niskin water samples
during the expedition. When taken, water samples for tracer analysis
were the first samples drawn from the 10-liter bottles. Care was taken
to co-ordinate the sampling of the tracers with other samples to
minimize the time between the initial opening of each bottle and the
completion of sample drawing. In most cases, dissolved oxygen, partial
pressure of CO2, dissolved inorganic carbon, and pH samples were
collected within several minutes of the initial opening of each
bottle. To minimize contact with air, the tracer samples were
collected from the Niskin bottle petcock into 250-cc ground glass
syringes through plastic 3-way stopcocks. The syringes were stored in
the dark in a large ice chest in the laboratory at 3.5º - 6º C until
30-45 minutes before analysis to reduce the degassing and bubble
formation in the sample. At that time, they were transferred to a
water bath at approximately 35º C to warm the samples prior to
analysis in order to increase the stripping efficiency.

Concentrations of CFC-11, CFC-12, SF_6, and N_2O in air samples,
seawater and gas standards were measured by shipboard electron capture
gas chromatography (EC-GC). This system from the University of
Washington was located in a portable laboratory on the fantail.
Samples were introduced into the EC-GC via a purge and trap system.
Approximately 200-ml water samples were purged with nitrogen and the
compounds of interest were trapped on a Porapak Q/Carboxen
1000/Molecular Sieve 5A trap cooled by an immersion bath to >-55ºC.
During the purging of the sample (6 minutes at 170 ml min-1 flow), the
gas stream was stripped of any water vapor via a Nafion trap in line
with an ascarite/magnesium perchlorate dessicant tube prior to
transfer to the trap. The trap was then isolated and heated by direct
resistance to 175ºC. The desorbed contents of the trap were back-
flushed and transferred onto the analytical pre-columns. The first
precolumn was a 40-cm length of 1/8-in tubing packed with 80/100 mesh
Porasil B. This precolumn was used to separate the CFC-11 from the
other gases. The second pre-column was 13 cm of 1/8-in tubing packed
with 80/100 mesh molecular sieve 5A. This pre-column separated the
N_2O from CFC-12 and SF_6. Three analytical columns in three gas
chromatographs with electron capture detectors were used in the
analysis. CFC-11 was separated from other compounds (e.g. CFC-113 and
CCl4) by a column consisting of 36 cm of Porasil B and 150 cm of
Carbograph 1AC maintained at 80ºC. CFC-12 and SF_6 were analyzed using
a column consisting of 2.33 m of molecular sieve 5A and 1.5 m of
Carbograph 1AC maintained at 80ºC. The analytical column for N_2O was
30 cm of molecular sieve 5A in a 120ºC oven. The carrier gas for this
column was instrumental grade P-5 gas (95% Ar / 5% CH4) that was
directed onto the second precolumn and into the third column for the
N_2O analyses. The detectors for the CFC-11, and for CFC-12 and SF_6
analyses were operated at 300ºC. The detector for N_2O was maintained
at 320 ºC.

The analytical system was calibrated frequently using a standard gas
of known gas composition. Gas sample loops of known volume were
thoroughly flushed with standard gas and injected into the system. The
temperature and pressure were recorded so that the amount of gas
injected could be calculated. CFC concentrations in air and seawater
samples were determined by fitting their chromatographic peak areas to
multi-point calibration curves, generated by injecting multiple sample
loops of gas from a working standard (UW WRS 32399) into the
analytical instrument. A full range of calibration points were run at
the beginning and end of the cruise, as well as during long
transits/weather delays when possible. The procedures used to transfer
the standard gas to the trap, precolumns, main chromatographic columns
and EC detectors were similar to those used for analyzing water
samples. Single injections of a fixed volume of standard gas at one
atmosphere were run much more frequently (at intervals of 2 hours) to
monitor short-term changes in detector sensitivity. Air samples and
system blanks (injections of loops of CFC-free gas) were injected and
analyzed in a similar manner. The typical analysis time for samples
was 740 sec.

For atmospheric sampling, an ~100 meter length of 3/8-in OD Dekaron
tubing was run from the portable laboratory to the bow of the ship. A
flow of air was drawn through this line to the main laboratory using
an Air Cadet pump. The air was compressed in the pump, with the
downstream pressure held at ~1.5 atm. using a back-pressure regulator.
A tee allowed a flow (100 ml min-1) of the compressed air to be
directed to the gas sample valves of the CFC/SF_6/N_2O analytical
system, while the bulk flow of the air (>7 l min-1) was vented through
the back-pressure regulator. Air samples were generally analyzed when
the relative wind direction was within 50 degrees of the bow of the
ship to reduce the possibility of shipboard contamination. The pump
was run for approximately 30 minutes prior to analysis to insure that
the air inlet lines and pump were thoroughly flushed. The average
atmospheric concentrations determined during the cruise (from sets of
3 or 4 measurements analyzed when possible) were 221.9 +/- 1.8 parts
per trillion (ppt) for CFC-11 (n=27), 496.6+/- 1.8 ppt for CFC-12
(N=40), 10.8 +/- 0.2 ppt for SF_6 (N=15), and 332.9 +/- 2.0 parts per
billion for N_2O (N=19).

Concentrations of the CFCs in air, seawater samples and gas standards
are reported relative to the SIO98 calibration scale [Prinn00].
Concentrations in air and standard gas are reported in units of mole
fraction in dry gas, and are typically in the parts per trillion (ppt)
range for CFCs and SF_6 and parts per billion (ppb) for N_2O.
Dissolved CFC concentrations are given in units of picomoles per
kilogram seawater (pmol/kg), SF_6 in femtomoles per kilogram seawater
(fmol/kg), and N_2O in nanomoles per kilogram seawater (nmol/kg).
Estimated limit of detection is 1 fmol/kg for CFC-11, 1 fmol/kg for
CFC-12 and 0.01 fmol/kg for SF_6.

The efficiency of the purging process was evaluated by re-stripping
water samples and comparing the residual concentrations to initial
values. These re-strip values were less than 1% for CFC-11 and
essentially zero for CFC-12 and SF_6. Based on the re-strips of
numerous samples where the stripper blank was low and relatively
constant, the mean values for N_2O were approximately 5-10% during the
cruise.

On this expedition, based on the analysis of 40 duplicate samples
(i.e. two syringe samples collected from the same Niskin), we estimate
precisions (1 standard deviation) of 0.65% or 0.0012 pmol/kg
(whichever is greater) for dissolved CFC-11, 0.36% or 0.00058 pmol/kg
for CFC-12 measurements, 0.017 fmol/kg or 1.98% for SF_6, and 0.67% or
0.096 nmol/kg for N_2O.


Analytical Difficulties/Acknowledgements
----------------------------------------

During A20, two immersion coolers failed – the first lost coolant
through a leak during transport to the start of A20; the second had
its low-stage compressor fail during the transit after the completion
of the measurement program of A20. Without an immersion cooler for the
trapping process, we would have only been able to measure CFC-12 for
A22. Thanks to the efforts of Dana Greeley, Eric Wisegarver, the
shipping department at NOAA-PMEL and the tracer measurement lab at
NOAA-PMEL, a spare working immersion cooler was located, tested, and
shipped to St. Thomas in advance of the departure for A22. We were
only able to make high-precision measurements during this cruise due
to the efforts, above and beyond, of the people listed above. These
individuals deserve the credit for the quality of the reported data.

[Prinn00] Prinn, R. G., Weiss, R.F., Fraser, P.J., Simmonds, P.G.,
          Cunnold, D.M., Alyea, F.N., O’Doherty, S., Salameh, P.,
          Miller, B.R., Huang, J., Wang, R.H.J., Hartley, D.E., Harth,
          C., Steele, L.P., Sturrock, G., Midgley,  P.M., McCulloch,
          A., 2000. A history of chemically and radiatively important
          gases in air deduced from ALE/GAGE/AGAGE.  Journal of
          Geophysical  Research, 105, 17,751-17,792


Dissolved Organic Carbon and Total Dissolved Nitrogen
=====================================================

PI
   * 3. Carlson (UCSB)

Technician
   * Chance English (UCSB)

Analysts
   * Keri Opalk

   * Elisa Halewood

Support
   NSF


Project Goals
-------------

The goal of the DOM project is to evaluate dissolved organic carbon
(DOC) and total dissolved nitrogen (TDN) concentrations along the A22
meridional transect occupied between April and May 2021.


Sampling
--------

DOC profiles were taken at every other station from every depth
sampled by the CTD (45 stations) DOC samples were passed through an
inline filter holding a combusted GF/F filter attached directly to the
Niskin for samples in the top 500 m of each cast. This was done to
eliminate particles larger than 0.6 µm from the sample. Samples from
deeper depths were not filtered. Previous work has demonstrated that
there is no resolvable difference between filtered and unfiltered
samples in waters below the upper 500 m at the µmol kg-1 resolution.
All samples were rinsed 3 times with about 5 mL of seawater and
collected into combusted 40 mL glass EPA vials. Samples were fixed
with 75 uL of 4N Hydrochloric acid and stored at room temperature on
board. Samples were shipped back to UCSB for analysis via high
temperature combustion on Shimadzu TOC-V or TOC L analyzers.

Sample Vials were prepared for this cruise by soaking in 10%
Hydrochloric acid, followed by a 3 times rinse with DI water. The
vials were then combusted at 450ºC for 4 hours to remove any organic
matter. Vial caps were cleaned by soaking in DI water overnight,
followed by a 3 times rinse with DI water and left out to dry.

Sampling goals for this cruise were to continue high resolution, long
term monitoring of DOC distribution throughout the water column, in
order to help better understand biogeochemical cycling in global
oceans.


Standard Operating Procedure for DOC analyses – Carlson Lab UCSB
----------------------------------------------------------------

DOC samples will be analyzed via high temperature combustion using a
Shimadzu TOC-V or Shimadzu TOC-L at an in shore based laboratory at
the University of California, Santa Barbara. The operating conditions
of the Shimadzu TOC-V have been slightly modified from the
manufacturer’s model system. The condensation coil has been removed
and the headspace of an internal water trap was reduced to minimize
the system’s dead space. The combustion tube contains 0.5 cm Pt
pillows placed on top of Pt alumina beads to improve peak shape and to
reduce alteration of combustion matrix throughout the run. CO_2 free
carrier gas is produced with a Whatman® gas generator [Carlson2010].
Samples are drawn into a 5 ml injection syringe and acidified with 2M
HCL (1.5%) and sparged for 1.5 minutes with CO_2 free gas. Three to
five replicate 100 µl of sample are injected into a combustion tube
heated to 680º. The resulting gas stream is passed though several
water and halide traps, including an added magnesium perchlorate trap.
The CO_2 in the carrier gas is analyzed with a non-dispersive infrared
detector and the resulting peak area is integrated with Shimadzu
chromatographic software. Injections continue until the at least three
injections meet the specified range of a SD of 0.1 area counts, CV
:math:>>`<<leq`2% or best 3 of 5 injections.

Extensive conditioning of the combustion tube with repeated injections
of low carbon water (LCW) and deep seawater is essential to minimize
the machine blanks. After conditioning, the system blank is assessed
with UV oxidized low carbon water. The system response is standardized
daily with a four-point calibration curve of potassium hydrogen
phthalate solution in LCW. All samples are systematically referenced
against low carbon water and deep Sargasso Sea (2600 m) or Santa
Barbara Channel (400 m) reference waters and surface Sargasso Sea or
Santa Barbara Channel sea water every 6 – 8 analyses [Hansell1998].
The standard deviation of the deep and surface references analyzed
throughout a run generally have a coefficient of variation ranging
between 1-3% over the 3-7 independent analyses (number of references
depends on size of the run). Daily reference waters were calibrated
with DOC CRM provided by D. Hansell (University of Miami;
[Hansell2005]).


DOC Calculation
~~~~~~~~~~~~~~~

   \mu\text{MC} = \frac{\text{average sample area} - \text{average
   machine blank area}}{\text{slope of std curve}}


Standard Operating Procedure for TDN analyses – Carlson Lab UCSB
----------------------------------------------------------------

TDN samples were analyzed via high temperature combustion using a
Shimadzu TOC-V with attached Shimadzu TNM1 unit at an in-shore based
laboratory at the University of California, Santa Barbara. The
operating conditions of the Shimadzu TOC-V were slightly modified from
the manufacturer’s model system. The condensation coil was removed and
the headspace of an internal water trap was reduced to minimize the
system’s dead space. The combustion tube contained 0.5 cm Pt pillows
placed on top of Pt alumina beads to improve peak shape and to reduce
alteration of combustion matrix throughout the run. Carrier gas was
produced with a Whatman® gas generator [Carlson2010] and ozone was
generated by the TNM1 unit at 0.5L/min flow rate. Three to five
replicate 100 µl of sample were injected at 130mL/min flow rate into
the combustion tube heated to 680ºC, where the TN in the sample was
converted to nitric oxide (NO). The resulting gas stream was passed
through an electronic dehumidifier. The dried NO gas then reacted with
ozone producing an excited chemiluminescence NO_2 species [Walsh1989]
and the fluorescence signal was detected with a Shimadzu TNMI
chemiluminescence detector. The resulting peak area was integrated
with Shimadzu chromatographic software. Injections continue until at
least three injections meet the specified range of a SD of 0.1 area
counts, CV :math:>>`<<leq`2% or best 3 of 5 injections.

Extensive conditioning of the combustion tube with repeated injections
of low nitrogen water and deep seawater was essential to minimize the
machine blanks. After conditioning, the system blank was assessed with
UV oxidized low nitrogen water. The system response was standardized
daily with a four-point calibration curve of potassium nitrate
solution in blank water. All samples were systematically referenced
against low nitrogen water and deep Sargasso Sea reference waters
(2600 m) and surface Sargasso Sea water every 6 – 8 analyses
[Hansell1998]. Daily reference waters were calibrated with deep CRM
provided by D. Hansell (University of Miami; [Hansell2005]).

Dissolved organic nitrogen (DON) concentrations are calculated as the
difference between TDN and DIN. Samples with less than 10 µmol/kg DIN
are most reliable estimates of DON.


TDN calculation
~~~~~~~~~~~~~~~

   \mu\text{MN} = \frac{\text{average sample area} - \text{average
   machine blank area}}{\text{slope of std curve}}

[Carlson2010] Carlson, C. A., D. A. Hansell, N. B. Nelson, D. A.
              Siegel, W. M. Smethie, S. Khatiwala, M. M. Meyers and E.
              Halewood 2010. Dissolved organic carbon export and
              subsequent remineralization in the mesopelagic and
              bathypelagic realms of the North Atlantic basin. Deep
              Sea Research II, 57: 1433-1445.

[Hansell1998] Hansell, D.A. and C.A. Carlson 1998. Deep ocean
              gradients in the concentration of dissolved organic
              carbon. Nature, 395: 263-266.

[Hansell2005] Hansell, D.A. 2005  Dissolved Organic Carbon Reference
              Material Program.  EOS, 35:318-319.

[Walsh1989] Walsh, T.W., 1989.  Total dissolved nitrogen in seawater:
            a new high-temperature combustion method and a comparison
            with photo-oxidation. Mar. Chem., 26:295-311.


Carbon Isotopes in Seawater (14/13C)
====================================

PI
   * Roberta Hansman (WHOI)

   * Rolf Sonnerup (UW)

Technician
   * Chance English (UCSB)

A total of 16-32 samples were collected from 13 stations along the A22
meridional transect. Samples were taken from 16 or 32 bottles from
stations deemed “shallow” or “deep”, respectively. Shallow stations
were sampled to approximately 1500m and deep stations were sampled
through the full depth of the station. Duplicates were made at 8
separate stations from one of the 16 or 32 niskin bottles sampled
during a cast. Samples were collected in 500 mL airtight glass
bottles. Using silicone tubing, the flasks were rinsed 2 times with
seawater from the surface niskin. While keeping the tubing at the
bottom of the flask, the flask was filled and flushed by allowing it
to overflow 1.5 times its volume. Once the sample was taken, about 10
mL of water was removed to create a headspace and 120 L of 50%
saturated mercuric chloride solution was added to the sample. To avoid
contamination, gloves were used when handling all sampling equipment
and plastic bags were used to cover any surface where sampling or
processing occurred.

After each sample was taken, the glass stoppers and ground glass joint
were dried and Apiezon-M grease was applied to ensure an airtight
seal. Stoppers were secured with a large rubber band wrapped around
the entire bottle. Samples were stored in AMS crates in the ship’s dry
laboratory. Samples were delivered to WHOI for analysis.

The radiocarbon/DIC content of the seawater (DI14C) is measured by
extracting the inorganic carbon as CO_2 gas, converting the gas to
graphite and then counting the number of 14C atoms in the sample
directly using an accelerated mass spectrometer (AMS).

Radiocarbon values will be reported as 14C using established
procedures modified for AMS applications. The 13C/12C of the CO_2
extracted from seawater is measured relative to the 13C/12C of a CO_2
gas standard calibrated to the PDB standard using and isotope radio
mass spectrometer (IRMS) at NOSAMS.


Stations sampled
^^^^^^^^^^^^^^^^

+-----------------------------------+-----------------------------------+-----------------------------------+
| 6 (shallow)                       | 12 (shallow)                      | 16 (duplicate only)               |
+-----------------------------------+-----------------------------------+-----------------------------------+
| 18 (deep)                         | 36 (deep)                         | 40 (deep)                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| 46 (shallow)                      | 50 (deep)                         | 54 (shallow)                      |
+-----------------------------------+-----------------------------------+-----------------------------------+
| 60 (deep)                         | 66 (shallow)                      | 72 (deep)                         |
+-----------------------------------+-----------------------------------+-----------------------------------+
| 76 (shallow)                      | 82 (deep)                         |                                   |
+-----------------------------------+-----------------------------------+-----------------------------------+


LADCP
=====

PI
   * Dr. Andreas Thurnherr (LDEO)

Cruise Participant
   * Ali Siddiqui (JHU)


Data Acquisition and QC
-----------------------

In order to collect full-depth profiles of horizontal and vertical
ocean velocity, two Acoustic Doppler Current Profilers (ADCPs), one
facing upward (uplooker) and the other downward (downlooker), as well
as a Deep Sea Power And Light rechargeable 48V battery and cables were
installed on the CTD rosette. This lowered ADCP (LADCP) system was
provided by the Lamont-Doherty Earth Observatory. The LADCP system is
self contained, requiring on-deck cable connections to charge the
battery and for communicating with the ADCPs. The battery charger was
affixed to an elevated cable run in the CTD bay and connected to a
long power cord extension terminating on a bench in the wet lab next
to the bulkhead door leading to the CTD bay. On the bench, the LADCP
data acquisition computer, a Mac Mini, as well as two bench-top power
supplies for the ADCPs were installed.

Between casts the LADCP system in the CTD bay was left connected to
the (unpowered) battery charger, as well as to the two deck cables
leading to the data acquisition computer and to the bench-top power
supplies. The male plug of the (disconnected) adapter cable between
the battery and the LADCP star cable was dummied up. While the deck
cables in the wet lab were permanently connected to the acquisition
computer with RS232-to-USB adapters, the corresponding power
connectors were left disconnected from the bench-top power supplies.
With this setup there is no voltage on any of the LADCP cables on the
rosette.

A few minutes before the CTD was moved out of the bay for deployment
the battery was disconnected from the charger and connected to the
ADCPs via an adapter cable and the star cable, both permanently
installed on the rosette. The male connector of the battery charger
cable was dummied up. In order to start data acquisition, the
instruments were woken up by the acquisition computer, the data from
the previous cast deleted from their built-in memory cards, and the
instruments were programmed to start pinging. Finally the two deck
cables were disconnected from the pig-tails that were also permanently
installed on the rosette in order to protect the expensive star cable
from unnecessary wear. The deck cables and pig tail connectors were
dummied up and the latter were secured to the rosette with a velcro
strap to avoid whipping during the casts. Once everything was set up,
the CTD operator and/or the marine tech were notified that the LADCP
system was ready for deployment. Deployment information was logged on
LADCP log sheets either when the data acquisition was started or once
the CTD system had entered the water.

After the CTD had been secured in the bay after each cast the velcro
securing the dummied up pig-tail ends to the rosette was removed, the
dummied up pig-tail ends were rinsed with fresh water, the dummy plugs
were removed, and the pig tails were connected to the deck cables.
Using the acquisition computer, LADCP data acquisition was stopped
after which the data download was initiated. Afterwards the two bench
top power supplies were connected to the deck cables in the lab, the
battery was disconnected from the adapter cable on the rosette, the
male end of the battery adapter cable on the rosette with two exposed
pins now carrying 48V (from the bench-top power supplies) was dummied
up, and the battery cable was attached to the (still unpowered)
charger cable. Afterwards power was applied to the battery charger in
the wet lab and the time noted on the LADCP log sheet.

After the data from the cast had finished downloading (after about 20
minutes on deep casts), the bench top power supplies were disconnected
from the deck cables in the lab. Then the data files were checked by
integrating the measured vertical velocities in time, which yields
estimates for the maximum depth (zmax) and the end depth (zend) of the
profile, both of which were recorded on the log sheet. After the
battery was fully charged (usually about an hour after charging was
initiated, as indicated by LEDs on the charger) the charger was
disconnected from power in the wet lab and the time was noted on the
log sheet. At this stage, the LADCP system was ready for the next
cast.

Communication between the acquisition computer and the ADCPs was
handled by a new acquisition software (acquire2), implemented as a set
of UNIX shell commands designed to minimize the possibility of
operator errors. Three different commands are used:

*Lstart*: This command wakes the instruments, lists their memory
contents, clears the memory (after operator confirmation) and programs
the instruments to start pinging by uploading command files. CTD
station and cast numbers must be provided by the operator since the
LADCP files use an independent numbering scheme. (CTD station and cast
information, as well as the LADCP profile number were noted on the
LADCP log sheet.)

*Ldownload*: This command interrupts the running data acquisition,
downloads the data and backs up the data files to a network drive.

*Lcheck*: This command integrates the measured vertical velocities
from both ADCPs to estimate zmax and zend, which are displayed
together with other useful profile statistics before the data files
are backed up (again) on the network drive.

While these three commands are all that is needed for LADCP data
acquisition, a fourth command (Lreset) is available for resetting the
ADCPs after swapping instruments and in case of communications
problems, of which there were none during this cruise.

Once or twice a day the LADCP and CTD time-series data were
transmitted with rsync to Thurnherr’s lab, where the data were
processed for horizontal velocity using the LDEO_IX processing
software and for vertical velocity using the LADCP_w processing
software. Important diagnostic plots were inspected in the lab, and
summary plots for every profile together with a short written
assessment was emailed back to the vessel and filed in a ring binder.
In addition to these processing diagnostics, LADCP data quality was
continuously monitored by creating section plots, some of which can be
found in the narrative section of this cruise report. A comprehensive
post-cruise LADCP QC will be carried out by Thurnherr in his lab
before submission of the new data to the archives.


Instrumentation
---------------

A single 300kHz TRDI Workhose Monitor ADCP (WH300, s/n 12734), fitted
with a custom self-recording accelerometer/magnetometer package, was
installed as the uplooker during all casts. This was the same as used
in the first leg (A20). The data from the accelerometer/magnetometer
package will be downloaded after the instruments return to the lab and
used for QC and final processing if needed.

A second 300kHz TRDI Workhose Monitor ADCP (WH300 s/n 24477) was used
as the downlooker during the entire A22 cruise. The same instrument
was used for profiles 53-90 in the first leg as well.

While both the ADCPs performed well, there was an error in data
acquisition at station 9 and 10. The downlooker ADCP was recording
data in two separate files, which indicated a power supply issue
during downcast. The issue first appeared at station 9 and persisted
in station 10, at which point the non-spillable lead acid battery
mounted on the rosette (SN01283) was replaced with a separate fully
charged battery. A voltage of 51.3 V was measured using a multimeter
before installation. Along with the battery, the star cable along with
the deck cable pig tails were also replaced with new ones. It was
found that the error was resolved after this operation and both the
ADCPs were collecting data in a single file. However, while
reconnecting the star cable to the ADCPs, the uplooker and downlooker
connections were interchanged which led to the ADCP files of profiles
11-16 being mislabeled (DL instead of UL and vice versa). This issue
was subsequently resolved by simply switching the connections of the
two serial adapter connectors for the two ADCPs. There were no issues
up till station 51, when the uplooker ADCP started storing data in 2
files again. Since there was no data deterioration, it was decided to
not change the cables once again, instead a new deck cable along with
a battery star cable adapter were kept on stand by in case of any
potential issues. The data files for the rest of the cruise were
collected for the uplooker ADCP in 2 files. The processing software
however, had no issues dealing with it.


Figures
-------

The section plots shown in Figs. 1 & 2 show the zonal and meridional
LADCP velocities obtained from the 90 stations occupied.

   [image]Zonal velocity section for A22 using the LADCP data.

   [image]Meridional velocity section for A22 using the LADCP data.


Discrete pCO_2
==============

PIs
   * Rik Wanninkhof (NOAA/AOML)

Analysts
   * 14. Patrick Mears (CIMAS/RSMAS)


Sampling
--------

Samples were drawn from 11-L Niskin bottles into 500 ml glass bottles
using nylon tubing with a Silicone adapter that fit over the drain
cock. Bottles were first rinsed three times with ~25 ml of water. They
were then filled from the bottom, overflowing a bottle volume while
taking care not to entrain any bubbles. About 5 ml of water was
withdrawn to allow for expansion of the water as it warms and to
provide space for the stopper and tubing of the analytical system.
Saturated mercuric chloride solution (0.24 ml) was added as a
preservative. The sample bottles were sealed with glass stoppers
lightly covered with grease and were stored at room temperature for a
maximum of fourteen hours prior to being run.

The analyses for pCO_2 were done with the discrete samples at 20ºC. A
primary water bath was kept within 0.03ºC of the analytical
temperature; a secondary bath was kept within 0.3ºC the analytical
temperature. The majority of the samples were analyzed in batches of
twelve bottles, which took approximately 3.5 hours including the six
standard gases. When twelve bottles were moved into the primary water
bath for analyses, the next twelve bottles were moved into the
secondary water bath. No sample bottle spent less than two hours in
the secondary water bath prior to being moved to the analytical water
bath. Duplicate samples from the same Niskin were drawn to check the
precision of the sampling and analysis.

1302 samples were drawn from 50 CTD casts. Fifty sets of duplicate
bottles were drawn at numerous depths. The average relative standard
error was 0.11%, while the median relative error was 0.09%.

No serious errors occurred.


Analyzer Description
--------------------

The principles of the discrete pCO_2 system are described in
[Wanninkhof1993] and [Chipman1993]. The major difference in the
current system is the method of equilibrating the sample water with
the constantly circulating gas phase. This system uses miniature
membrane contactors (Micromodules from Memrana, Inc.), which contain
bundles of hydrophobic micro-porous tubes in polycarbonate shells (2.5
x 2.5 x 0.5 cm). The sample water is pumped over the outside of the
tubing bundles in two contactors in series at approximately 25 ml/min
and to a drain. The gas is recirculated in a vented loop, which
includes the tubing bundles and a non-dispersive infrared analyzer
(LI-COR™  model 840) at approximately 32 ml/min.

The flow rates of the water and gas are chosen with consideration of
competing concerns. Faster water and gas flows yield faster
equilibration. A slower water flow would allow collection of smaller
sample volume; plus a slower gas flow would minimize the pressure
increase in the contactor. Additionally, the flow rates are chosen so
that the two fluids generate equal pressures at the micro-pores in the
tubes to avoid leakage into or out of the tubes. A significant
advantage of this instrumental design is the complete immersion of the
miniature contactors in the constant temperature bath. Also in the
water bath are coils of stainless steel tubing before the contactors
that ensure the water and gas enter the contactors at the known
equilibration temperature.

The instrumental system employs a large insulated cooler (Igloo Inc.)
that accommodates twelve sample bottles, the miniature contactors, a
water circulation pump, a copper coil connected to a refrigerated
circulating water bath, an immersion heater, a 12-position sample
distribution valve, two thermistors, and two miniature pumps. The
immersion heater works in opposition to the cooler water passing
through the copper coil. One thermistor is immersed in the water bath,
while the second thermistor is in a sample flow cell after the second
contactor. The difference between the two thermistor readings was
consistently less than 0.02ºC during sample analyses. In a separate
enclosure are the 8-port gas distribution valve, the infrared
analyzer, a barometer, and other electronic components. The gas
distribution valve is connected to the gas pump and to six standard
gas cylinders.

To ensure analytical accuracy, a set of six gas standards (ranging
from 288 to 1534 ppm) was run through the analyzer before and after
every sample batch. The standards were obtained from Scott-Marin and
referenced against primary standards purchased from C.D. Keeling in
1991, which are on the WMO-78 scale.

A custom program developed using LabView™ controls the system and
graphically displays the CO_2 concentration as well as the
temperatures, pressures and gas flow during the 15-minute
equilibration. The analytical system was running well enough that the
equilibration period was shortened to 12 minutes for the second half
of the cruise. The CO_2 in the gas phase changes greatly within the
first minute of a new sample and then goes through nearly two more
oscillations. The oscillations dampen quickly as the concentration
asymptotically approaches equilibrium. The flows are stopped, and the
program records an average of ten readings from the infrared analyzer
along with other sensor readings. The data files from the discrete
pCO_2 program are reformatted so that a Matlab program designed for
processing data from the continuous pCO_2 systems can be used to
calculate the fugacity of the discrete samples at 20ºC. The details of
the data reduction are described in [Pierrot2009].

   [image]CO_2 oscillations during start of first sample in set of
   twelve

The instrumental system was originally designed and built by Tim
Newberger and was supported by C. Sweeney and T. Takahashi. Their
skill and generosity has been essential to the successful use and
modification of this instrumental system. Victoria Schoenwald assisted
in collecting samples.


Standard Gas Cylinders
^^^^^^^^^^^^^^^^^^^^^^

+------------+--------------------------+
| Cylinder # | ppm CO_2                 |
|============|==========================|
| JB03282    | 288.46                   |
+------------+--------------------------+
| JB03268    | 384.14                   |
+------------+--------------------------+
| CB11243    | 591.61                   |
+------------+--------------------------+
| CA05980    | 792.51                   |
+------------+--------------------------+
| CA05984    | 1036.95                  |
+------------+--------------------------+
| CA05940    | 1533.7                   |
+------------+--------------------------+

[Chipman1993] Chipman, D.W., J. Marra, and T. Takahashi, 1993: Primary
              production at 47ºN and 20ºW in the North Atlantic Ocean:
              A comparison between the 14C incubation method and mixed
              layer carbon budget observations. Deep-Sea Res., II, v.
              40, pp. 151-169.

[Wanninkhof1993] Wanninkhof, R., and K. Thoning, 1993: Measurement of
                 fugacity of CO2 in surface water using continuous and
                 discrete sampling methods. Mar. Chem., v. 44, no.
                 2-4, pp. 189-205.

[Pierrot2009] Pierrot, D., C. Neill, K. Sullivan, R. Castle,
              R.Wanninkhof, H. Luger, T. Johannessen, A. Olsen, R.A.
              Feely, C.E. Cosca, 2009: Recommendations for autonomous
              underway pCO2 measuring systems and data-reduction
              routines . Deep-Sea Res., II, v. 56, pp. 512-522.


Underway pCO_2
==============

PIs
   * Simone Alin (NOAA/PMEL)

Analysts
   * Andrew Collins (NOAA/PMEL)

The partial pressure of CO_2 (pCO_2) in the surface ocean was measured
throughout the duration of this expedition with a General Oceanics
8050 underway system. Uncontaminated seawater was continuously passed
(~2.8 l/min) through a chamber where the seawater concentration of
dissolved CO_2 was equilibrated with an overlying headspace gas. The
CO_2 mole fraction of this headspace gas (xCO2) was measured
approximately every three minutes via a non-dispersive infrared
analyzer (Licor 7000). Roughly every three hours, the system measured
four gas standards with known CO_2 concentrations certified by the
NOAA Earth Science Research Laboratory in Boulder, CO ranging from
~300 – 900 ppm CO_2. Additionally, a tank of 99.9995% ultra-high
purity nitrogen gas was measured as a baseline 0% CO_2 standard.
Following measurements of standard gases, six measurements of
atmospheric xCO2 were made of air supplied through tubing fastened to
the ships starboard jackstaff. Twice a day, the infrared analyzer was
calibrated via a zero and span routine using the nitrogen gas and the
highest concentration (872.6 ppm) CO_2 standard. In addition to
measurements of seawater xCO2, atmospheric xCO2, and standard gases,
several variables were monitored to evaluate system performance (e.g.
gas and water flow rates, pump speeds, equilibrator pressures, etc).
For more detail on the general design of this underway pCO_2 system,
see [Pierrot2009].

A Seabird (SBE) 38 temperature sensor located at the ship’s seawater
intake provided measurements of in situ seawater temperature, while a
SBE 45 thermosalinograph monitored temperature and salinity in the bow
of the ship before the seawater reached the pCO_2 system. An Aanderaa
4330 optode plumbed in line with the pCO_2 system water supply
measured dissolved oxygen (DO) continuously. Additionally, a modified
SeaFET system was also plumbed in line which measured pH throughout
the duration of the cruise.

A preliminary round of processing was performed on this dataset using
Matlab routines developed by Denis Pierrot of the Atlantic Oceanic and
Meteorological Lab in Miami, FL. In one brief (10 minute) instance,
the underway system was shut down for minor maintenance to be
performed. Two brief instances of data loss occurred when the ships
data transmission dropped, resulting in the loss of position,
temperature, salinity, etc data for 217 pCO_2 measurements. These
measurements will be merged with the pCO_2 dataset during the next
round of processing. Of 12,897 measurements, only 13 were assigned a
WOCE quality flag of 4 (bad measurement), all of which were due to
contamination of atmospheric measurements by exhaust from the ship. At
this time, no measurements were assigned a quality flag of 3
(questionable measurement). Measurements of gas standards were within
1% of their certified value throughout the duration of the expedition,
save for one brief initial period where the Licor demonstrated some
drift (Figure 1).

Preliminary review of collected data suggest that the main control on
the surface seawater carbonate system was temperature (Figure 2).
Excursions from thermodynamic controls on pCO_2, pH and DO were
measured in the northern section of the cruise on line W, where mild
undersaturation (~320 ppm) relative to atmospheric values of pCO_2
were measured. Concomitant changes were observed in discrete
measurements of pH, DO, DIC, and other variables. Fluorescence and
chlorophyll data suggest the presence of a prolonged phytoplankton
bloom, which likely explains these observations. However, further
evaluation of these data and the supplementary suite of discrete
surface CTD measurements that were collected is needed before the
controls on pCO_2, pH and DO can be fully elucidated.

This dataset should be considered preliminary; additional quality
control and quality assurance is needed before these data can be
considered final.

   [image]Difference between measurements made by the non-dispersive
   infrared analyzer (Licor 7000) of gas standards and the known
   certified value of those standards (in ppm CO_2).

   [image]Spatial distribution of relevant parameters (sea surface
   temperature [SST, ºC], sea surface salinity [PSU], fCO2 [ppm], air-
   sea fCO2 disequilibrium [ppm] and dissolved oxygen [µM]) measured
   by the underway pCO_2 system during the 2021 GO-SHIP A22 research
   expedition.

[Pierrot2009] Pierrot, D., Neill, C., Sullivan, K., Castle, R.,
              Wanninkof, R.W., Lüger, H., Johannessen, T., Olsen, A.,
              Feely, R.A., Cosca, C.E.; 2009. Recommendations for
              autonomous underway pCO2 measuring systems and data-
              reduction routines. Deep-Sea Research II 56 (2009)
              512–522


Float Deployments
=================

A total of 14 profiling floats from 3 different programs were deployed
during the 2021 A22 research cruise. 10 are part of the Core Argo
program (https://argo.ucsd.edu/) (8 WHOI, 2 Argo Canada - RBR pilot
program). The remaining 4 are part of the new Global Ocean
Biogeochemical Argo array (https://www.go-bgc.org/). Additionally, two
RAFOS floats were deployed as tests for Viviane Menezes upcoming Deep
Madagascar Basin (DMB) Experiment. Both Core and Go-GBC floats measure
temperature, salinity, and pressure. Go-BGC floats additionally
measure O_2, NO_3, pH, and bio-optics. Details for each float type
follow.


WHOI Core Argo Floats
---------------------

PIs
   * Susan Wijffels (WHOI)

   * Steven Jayne (WHOI)

   * Pelle Robbins (WHOI)

Shipboard personnel:
   * Jesse Anderson (WHOI)

   * Elizabeth Ricci (UW SSSG)

   * Stephen Jalickee (UW SSSG)

A total of 8 WHOI Core Argo floats were deployed during the A22
cruise. All floats were MRV Systems Solo II (S2-A) floats equipped
with Seabird SBE41-CP CTDs and Iridium antennas. Parameters measured
are temperature, salinity, and pressure. These floats were readied for
deployment by the skilled members of the WHOI float lab. Jessica Kozik
(WHOI) handled dockside logistics for getting the floats to the R/V
Thompson prior to the first leg of the A20/A22 cruise. Shock watches
indicated that the floats were handled properly during transport from
the WHOI float lab to the R/V Thompson main lab. Deployment training
was provided via videoconference prior to ship departure. All floats
were armed and ready for deployment prior to joining the ship. Pelle
Robbins (WHOI) determined float deployment locations, prioritizing
regions with coverage gaps for the target Argo spatial coverage. At
sea, R/V Thompson SSGs Elizabeth Ricci and Stephen Jalickee, and co-
chief scientist Jesse Anderson were in charge of deployments.
Additional assistance was provided by ABs and student CTD watch
standers. Float deployment boxes were packaged in plastic bags and
wrap to protect the cardboard boxes and cornstarch release harness.
Just before deployment, the plastic layers were removed. Then, a slip-
line and the 4 deployment bridle loops were passed through a
carabiner. After lifting the box over the stern, the boxes were
lowered to water level using the slip-line. All cornstarch water
releases worked as designed and the float boxes were released without
issues. Deployments occurred from the port stern while the ship slowly
steamed away from station.

All floats will complete standard Argo missions. The floats will drift
at 1,000 m then dive to 2,000 m before collecting data on the way back
up to the surface every 10 days. All floats are working well. Data is
publicly available via the Argo program GDACs.


Summary of the deployment details of the Core Argo floats
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| #              | S/N            | WMO ID         | Lat            | Lon            | Date/Time      | CTD Station    |
|                |                |                |                |                | (UTC)          |                |
|================|================|================|================|================|================|================|
| 1              | 7627           | 4903344        | 15.2679        | -69.0612       | 04/21/2021     | In transit     |
|                |                |                |                |                | 11:47          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 2              | 7670           | 4903349        | 14.1457        | -69.6996       | 04/24/2021     | 11             |
|                |                |                |                |                | 07:59          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 3              | 7673           | 4903351        | 15.19          | -69.51         | 04/24/2021     | 13             |
|                |                |                |                |                | 20:10          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 4              | 7671           | 4903350        | 17.0716        | -66.4696       | 04/26/2021     | 20             |
|                |                |                |                |                | 16:06          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 5              | 7668           | 4903347        | 19.691         | -65.998        | 04/30/2021     | 39             |
|                |                |                |                |                | 19:01          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 6              | 7653           | 4903345        | 21.8282        | -65.9188       | 05/02/2021     | 44             |
|                |                |                |                |                | 08:06          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 7              | 7669           | 4903348        | 25.3497        | -65.6969       | 05/04/2021     | 51             |
|                |                |                |                |                | 10:01          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 8              | 7657           | 4903346        | 26.8181        | -65.5993       | 05/05/2021     | 54             |
|                |                |                |                |                | 06:54          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+


Argo Canada
-----------

PIs
   * Clark Richards (BIO)

   * Blair Greenan (Argo Canada)

Shipboard personnel
   * Jesse Anderson (WHOI)

   * Elizabeth Ricci (UW SSSG)

   * Stephen Jalickee (UW SSSG)

2 profiling floats were deployed for Argo Canada. Both floats were NKE
Instrumentation ARVOR-I floats equipped with RBR CTDs and Iridium
antennas. These floats are part of the RBR Argo pilot program being
tested for the Core Argo float array. Data collected from these two
floats will be used to characterize RBR sensor dynamic response and
pressure corrections. Parameters measured are temperature, salinity,
and pressure. To aid in evaluating sensor performance, both floats
were deployed at roughly the same location following A22 CTD cast 18.
A companion float which is equipped with the CTD (SBE41-CP) used by
most Core Argo floats was also deployed at this location. The
deployment location in the Carribbean was chosen by Clark Richards to
take advantage of deep water stability and thermohaline staircases
when evaluating sensor responses.

After shipment from BIO to WHOI, Jessica Kozik (WHOI) readied the
floats for deployment. Jessica also handled dockside logistics in
Woods Hole prior to the preceding A20 cruise departure. Float
initialization and deployment training were provided by Clark Richards
via videoconference. At sea, Jesse Anderson started the float misson
by removing the magnets attached with Velcro approximately 45 minutes
before deployment. The expected slow 5 Ev and 5 pump activations were
heard. Following a full auto-test, the buzzers started indicating that
the floats were ready for deployment. The floats were deployed just
after a GO-BGC float  (UW float #19443, WMO # 5906437) while the ship
was slowly steaming away from station. Floats were lowered into the
water by a slip-line strung through the deployment collar hole. R/V
Thompson SSG Stephen Jalickee was the deployer with help from ABs on
watch.

The floats will complete Argo-type profile missions. Currently, the
floats are set to profile from 2,000 m to the surface every 2 days,
with a drift at 1,000 m between profiles. Data is collected during the
upward profile and data is transmitted via Iridium at the surface.
Both floats are performing well. Data is being processed by the MEDS
DAC and are available to the public via the Argo program GDAC.


Summary of the deployment details of the Argo Canada floats.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| #              | ID             | WMO ID         | Lat            | Lon            | Date/Time      | CTD Station    |
|                |                |                |                |                | (UTC)          |                |
|================|================|================|================|================|================|================|
| 1              | A13500-20CA001 | 4902533        | 16.5421        | -67.3423       | 04/26/2021     | 18             |
|                |                |                |                |                | 03:19          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+
| 2              | A13500-20CA002 | 4902534        | 16.5429        | -67.3409       | 04/26/2021     | 18             |
|                |                |                |                |                | 03:21          |                |
+----------------+----------------+----------------+----------------+----------------+----------------+----------------+


GO-BGC Argo Floats
------------------

PIs:
   * Kenneth Johnson (MBARI)

   * Steven Riser (UW)

   * Jorge Sarmiento (Princeton)

   * Lynne Talley (UCSD/SIO)

   * Susan Wijffels (WHOI)

Shipboard personnel:
   * Jesse Anderson (WHOI)

   * Elizabeth Ricci (UW SSSG)

   * Stephen Jalickee (UW SSSG)

4 biogeochemical (BGC) Argo floats were deployed on A22 as part of the
Global Ocean Biogeochemistry (GO-BGC) program (https://go-bgc.org),
which is funded by NSF Award 1946578. BGC Argo floats deployed during
A22 are among the first dozen floats deployed for this new program,
which is slated to grow to 500 floats globally over the next 5 years.
GO-BGC contributes to international and US BGC-Argo, and all floats
conform to Argo mission requirements. BGC-Argo floats will help to
resolve seasonal cycles of many key properties relevant to global
biogeochemical processes. The GO-BGC Atlantic sector is led by the
WHOI Argo group (Susan Wijffels, Roo Nicholson; planning Pelle
Robbins), who determined float deployment locations for A22 as well as
the preceding A20 cruise.

All floats deployed were UW-modified Teledyne Webb Apex floats
equipped with SBE41-CP CTDs, O_2, NO_3, pH, and FLBB bio-optical
sensors. The floats for the A20/A22 cruises were readied at the UW
float lab (S. Riser Argo lab) and shipped to WHOI. At WHOI, Argo
engineer Greg Brusseau (UW) tested each float and armed them for
deployment prior to being loaded on the R/V Thompson. WHOI provided
excellent high-bay lab space with an adjacent outdoor parking which
satisfied COVID-19 requirements for Greg to complete this work.
Workspace and dockside logistics were coordinated by Jessica Kozik
(WHOI). Deployment training was provided via videoconference.

At sea, R/V Thompson SSGs Elizabeth Ricci and Stephen Jalickee, and
co-chief scientist Jesse Anderson were in charge of deployments.
Before each deployment, Jesse Anderson carefully cleaned the NO_3 and
FLBB bio-optical sensors. Each sensor was rinsed with DI water,
wiped/dabbed with lens wipes, rinsed with DI water again, then
wiped/dabbed with lens paper. The floats were set to self-activate, so
sensor cleaning was the only pre-deployment preparation required.
Floats were deployed from the port stern as the ship steamed slowly
away from the CTD station. Floats were lifted over the stern, then
carefully lowered into the water with a slip-line strung through the
deployment collar of the float. Deployments were completed by SSGs
Elizabeth Ricci (deployment #2 and 3) and Stephen Jalickee (deployment
#1 and 4) with assistance from ABs on watch. Ben Freiberger (SIO)
helped with the last deployment. All deployments were clean with no
tangling or hangups of the slip-line.

All floats operate on a standard Argo profiling 10-day cycle. After an
initial test dive, the floats descend to a parking depth of 1000 m,
and then drift for 10 days with the ocean currents. After 10-days, the
floats dive to 2000 m and then ascend to the surface, during which
data are measured and saved. The data are then sent to shore via
Iridium Satellite communication All of the floats began reporting data
immediately and the sensors are operating well. The only exception is
UW float #19443 (WMO #5906437) which has not reported data from the
FLBB, potentially due to an issue with the cable. All data is publicly
available via the GO-BGC data portals and the Argo GDAC.

All deployments occurred at “full” carbon stations so that all GO-SHIP
carbon parameters were analyzed for each depth sampled (34 depths from
surface to 10 m off bottom). Additionally, duplicate bottles were
tripped at the surface (~5 m) and at the depth of the chlorophyll
maximum to allow for the addition of POC and HPLC sampling at these
stations. POC and HPLC samples were collected and filtered by the
SIO/ODF team (Susan Becker and Alexandra Fine) and will be sent frozen
for analysis at NASA for HPLC and SIO/UCSD for POC. Unfortunately, the
transmissometer had spikey data on CTD cast 58 (UW float #19531, WMO
#5906439) due to the tape covering the clamps coming loose.

All floats were adopted by different schools and organizations in the
US as part of the Adopt-a-float program (https://www.go-
bgc.org/outreach/adopt-a-float). Names and images provided by the
adoptees were skillfully drawn onto the floats by ODF team member
Caitlyn Webster (SIO). Each class received the details their
deployment from Jesse Anderson via email and photographs via posts to
the GO-BGC expeditions webpage by onshore personnel George Matsumoto
(MBARI). Together with their teachers, the students will follow the
float data, which can be easily downloaded and plotted from the
website.


Summary of the deployment details of the GO-BGC Argo floats
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| #            | UW ID        | WMO ID       | Lat          | Lon          | Date/Time    | CTD Station  | Adopt-a-Flo  |
|              |              |              |              |              | (UTC)        |              | at Name      |
|==============|==============|==============|==============|==============|==============|==============|==============|
| 1            | 19443        | 5906437      | 16.5421      | -67.3423     | 04/26/2021   | 18           | Comets       |
|              |              |              |              |              | 03:16        |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 2            | 19605        | 5906436      | 23.8226      | -65.792      | 05/03/2021   | 48           | The Dogie    |
|              |              |              |              |              | 13:08        |              | Diver        |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 3            | 19531        | 5906439      | 28.8169      | -65.4643     | 05/06/2021   | 58           | AHEA         |
|              |              |              |              |              | 10:17        |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+
| 4            | 19129        | 5906438      | 34.7433      | -66.5846     | 05/09/2021   | 70           | Integrity    |
|              |              |              |              |              | 21:34        |              |              |
+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+


RAFOS Float
-----------

PIs

   * Viviane Menezes (WHOI)

   * Heather Furey (WHOI)

Two acoustically-tracked RAFOS floats ballasted for 4000 m depth were
deployed in this cruise on station #56 (27.82N; 65.53W). These floats
are part of the Deep Madagascar Basin (DMB) Experiment funded by NSF
and lead by Viviane Menezes. The floats were released as an at-sea
test before the deployment of 73 floats scheduled for 2022 in the
South Indian Ocean. The float configuration at USVI port was conducted
by the chief-scientist Viviane Menezes and co-chief scientist Jesse
Anderson, and deployment by the marine technician Stephen Jalickee,
CTD watchstander Ali Siddiqui and chief-scientist Viviane Menezes.
Drop-weight serial number confirmation was done by Viviane Menezes and
checked by Ali Siddiqui. Configuration followed the instructions
prepared by Heather Furey, a research specialist at WHOI and co-PI in
the DMB.


Sofar Spotter Drifter Deployments
=================================

A total of 19 Sofar Ocean Technologies Spotter drifters were deployed
on the A22 cruise (https://www.sofarocean.com/products/spotter). Co-
chief scientist Jesse Anderson and R/V Thompson SSGs Elizabeth Ricci
and Stephen Jalickee were in charge of the deployments. Additional
assistance was provided by multiple science party members. The
drifters were deployed by dropping them over the port stern while the
vessel steamed away from station or during transits between stations.
Parameters measured are complete wave spectrum and winds (speed and
direction, derived from wave spectra). All spotters deployed are
working well. Data will be publicly available as per Level 3 data
requirements of the GO-SHIP program.

SOFAR technologies provided the following description: Sofar Ocean
Technologies is deploying a global free-floating metocean sensor array
which develops new assimilation strategies to im- prove global ocean
weather forecast models. The network of Sofar buoys make observations
of real-time ocean conditions including surface winds, waves and
currents, and transmit the data back to shore through an integrated
satellite connection. Sofar is working to expand its coverage in the
Atlantic, Indian, and Southern Oceans by utilizing Ship of Opportunity
partner groups, with all data from the global network publicly
available in real time through the Sofar Weather Dashboard. Data
exports are also available to partner groups as part of our research
grants program, either directly to deployment partners, or through our
Climate Initiative. Sofar’s work is funded in part by the US Office of
Naval Research, which has sponsored several research projects
including an upcoming effort to directly observe hurricane activity in
the Atlantic in order to improve hurricane forecasting and operational
tracking systems.


Summary of the deployment details of the Sofar. Stations marked with * had deployment information reconstructed from ship records and CTD console logs.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

+------------------+------------------+------------------+------------------+------------------+------------------+
| Deployment       | ID               | Lat              | Lon              | Date and Time    | CTD Station      |
|                  |                  |                  |                  | (UTC)            |                  |
|==================|==================|==================|==================|==================|==================|
| 1                | 1171             | 23.82            | -65.79           | 05/03/2021 13:08 | 48               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 2                | 1177             | 24.33            | -65.76           | 05/03/2021 20:06 | 49               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 3                | 1186             | 24.82            | -65.73           | 05/04/2021 03:10 | 50               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 4                | 1035             | 25.35            | -65.70           | 05/04/2021 10:02 | 51               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 5                | 1169             | 25.81            | -65.66           | 05/04/2021 16:40 | 52               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 6                | 1180             | 26.82            | -65.60           | 05/05/2021 06:54 | 54               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 7                | 1185             | 27.82            | -65.53           | 05/05/2021 20:48 | 56               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 8                | 1175             | 34.74            | -66.58           | 05/09/2021 21:34 | 70               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 9                | 1187             | 35.72            | -67.17           | 05/10/2021 11:18 | 72               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 10               | 1189             | 37.14            | -68.06           | 05/12/2021 04:44 | 75               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 11               | 1062             | 37.39            | -68.22           | 05/12/2021 11:42 | 76               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 12*              | 1168             | 37.52            | -68.30           | 05/12/2021 12:40 | between 76/77    |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 13*              | 1182             | 37.63            | -68.33           | 05/12/2021 18:10 | 77               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 14*              | 1094             | 37.74            | -68.44           | 05/12/2021 19:20 | between 77/78    |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 15*              | 1183             | 37.85            | -68.43           | 05/13/2021 00:40 | 78               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 16*              | 0986             | 37.99            | -68.58           | 05/13/2021 02:15 | between 78/79    |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 17*              | 1178             | 38.11            | -68.56           | 05/13/2021 07:51 | 79               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 18*              | 1176             | 38.33            | -68.86           | 05/13/2021 13:10 | 80               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 19*              | 1194             | 38.56            | -68.03           | 05/13/2021 18:40 | 81               |
+------------------+------------------+------------------+------------------+------------------+------------------+


Chipods
=======

PI
   * Jonathan Nash (OSU)


Overview
--------

Chipods are instrument packages that measure turbulence and mixing in
the ocean. Specifically, they are used to compute turbulent
diffusivity of heat (K) which is inferred from measuring dissipation
rate of temperature variance (\chi) from a shipboard CTD. Chipods are
self-contained, robust and record temperature and derivative signals
from FP07 thermistors at 100 Hz; they also record sensor motion at the
same sampling rate. Details of the measurement and our methods for
processing \chi can be found in [Moum_and_Nash2009]. In an effort to
expand our global coverage of deep ocean turbulence measurements, the
ocean mixing group at Oregon State University has supported chipod
measurements on all of the major global repeat hydrography cruises
since December 2013.


System Configuration and Sampling
---------------------------------

Three chipods were mounted on the rosette to measure temperature (T),
its time derivative (dT/dt), and x and z (horizontal and vertical)
accelerations at a sampling rate of 100 Hz. Two chipods were oriented
such that their sensors pointed upward. The third one was pointed
downward.

The up-looking sensors were positioned higher than the Niskin bottles
on the rosette in order to avoid measuring turbulence generated by
flow around the rosette and/or its wake while its profiling speed
oscillates as a result of swell-induced ship-heave. The down-looking
sensors were positioned as far from the frame as possible and as close
to the leading edge of the rosette during descent as possible to avoid
measuring turbulence generated by the rosette frame and lowered ADCP.

The chipods were turned on by connecting the sensors to the pressure
case at the beginning of the cruise. They continuously recorded data
until the end of the leg. The sensors had no issues of note this
cruise. Two end caps were lost and replacements were printed using
TGT’s 3D printer. The printed caps broke on multiple occasions, with
additionals being printed as needed.

   [image]Upward-looking chipod sensors attached to the rosette.

   [image]Downward-looking chipod sensor attached to the rosette.

   [image]Highly sensitive temperature probe, which is sampled at
   100Hz.

+------------------+--------------------+-----------------+------------------------+
| Logger Board SN  | Pressure Case SN   | Up/Down Looker  | Cast Used              |
|==================|====================|=================|========================|
| 2027             | Ti 44-3            | Up              | 901-90                 |
+------------------+--------------------+-----------------+------------------------+
| 2030             | Ti 44-11           | Up              | 901-90                 |
+------------------+--------------------+-----------------+------------------------+
| 2008             | Ti 44-5            | Down            | 901-90                 |
+------------------+--------------------+-----------------+------------------------+

[Moum_and_Nash2009] Moum, J., and J. Nash, Mixing Measurements on an
                    Equatorial Ocean Mooring, Journal of Atmospheric
                    and Oceanic Technology, 26(2), 317–336, 2009


Underwater Vision Profiler 5 HD (UVP)
=====================================

PI
   * Andrew McDonnell (University of Alaska, Fairbanks)

Cruise Participant
   * Stephanie O’Daly (Lead; University of Alaska, Fairbanks)

   * Ali Siddiqui (Secondary; Johns Hopkins University)


System Configuration and Sampling
---------------------------------

The Underwater Vision Profiler 5 (UVP5) HD serial number 207 was
programmed, mounted on the rosette, and charged. The UVP5 is outfitted
with a High Definition 4 Mp camera with an acquisition frequency of up
to 20 Hz. This optical imaging device obtains in situ concentrations
and images of marine particles and plankton throughout the water
column, capturing objects sized ~100 µm to several cm in diameter. The
camera of the UVP5 HD is different from the previous non-HD version,
but the operations are identical for both. The instrument and data
processing are described in [Picheral2010]. Depth trigger mode was
used throughout the entirety of the cruise, programmed to turn on at
15 m with a maximum depth of 6000 m. A 20 m soak for one minute was
used throughout the cruise. The UVP turned on and off as expected for
all cruise stations using this configuration.


General Particle Patterns
-------------------------

Near South America, we see low particle abundance overall with a
strong surface and often present subsurface particle abundance maximum
(Fig. 1). A deep nephloid layer generally was not present.
Additionally, we observed a moderate mean particle size at all depths.
Moving further north, but still south of the Gulf Stream, we see even
lower particle abundance with a smaller mean particle size (Fig. 2).
In the Gulf Stream, we see elevated particle abundance at the surface
with a very strong deep nephloid layer signal at depth with a smaller
mean particle size at all depths (Fig. 3). Stations north of the Gulf
Stream were consistent with very high particle abundance at the
surface with a slightly elevated particle abundance at depth
indicating a slight deep nephloid layer signal at depth (Fig. 4). We
saw a higher mean particle size at all depths in this region.


Future Data Analysis
--------------------

Total image count gathered during the cruise was 628,260 images. A
combination of machine learning and manual validation will be used to
sort images using the Ecotaxa database. Images will be sorted into
various zooplankton taxa and detrital categories. Zooplankton
categories will include crustacea (including copepods and krill),
gelatinous (larvacean, jellyfish, salps), and rhizaria. Examples of
these images are shown in Fig. 5.


Problems
--------

At the test station, the UVP turned on during the initial 20 m soak
and sampled during the downcast. When the rosette was at 300m the cast
was aborted to remove tubing from the pump. The UVP turned off during
the up cast, as expected. The CTD was redeployed, but the UVP did not
turn on during the 20 m soak and did not sample during the downcast. I
believe the UVP needed to be on deck longer to allow the camera to
fully turn off after the initial cast. We didn’t have to abort any
other casts on this cruise, so I was not able to test this hypothesis.
To be safe, in the future it would probably be best to unplug and re-
plug the power shunt between casts after aborted casts.


Figures
-------

   [image]Examples of preliminary profiles at station 8. Plots show
   total large particulate matter (LPM) abundance, mean grey level
   (brightness) of LPM, and equivalent spherical diameter (ESD)
   (right) and particle concentration in size bins (left) both plotted
   against depth (meters). Near South America, we see low particle
   abundance overall with a surface and subsurface particle abundance
   maximum. A deep nephloid layer is not present and with there is a
   medium mean particle size at all depths.

   [image]Examples of preliminary profiles at station 46. Plots show
   total large particulate matter (LPM) abundance, mean grey level
   (brightness) of LPM, and equivalent spherical diameter (ESD)
   (right) and particle concentration in size bins (left) both plotted
   against depth (meters). South of the Gulf Stream, we see low
   particle abundance with a smaller mean particle size.

   [image]Examples of preliminary profiles at station 73. Plots show
   total large particulate matter (LPM) abundance, mean grey level
   (brightness) of LPM, and equivalent spherical diameter (ESD)
   (right) and particle concentration in size bins (left) both plotted
   against depth (meters). In the Gulf Stream, we see elevated
   particle abundance at the surface with a very strong deep nephloid
   layer signal at depth and a smaller mean particle size.

   [image]:  Examples of preliminary profiles at station 86. Plots
   show total large particulate matter (LPM) abundance, mean grey
   level (brightness) of LPM, and equivalent spherical diameter (ESD)
   (right) and particle concentration in size bins (left) both plotted
   against depth (meters). North of the Gulf Stream, we see very high
   particle abundance at the surface with a slight deep nephloid layer
   signal at depth and a higher mean particle size.

   [image]Examples of particle and plankton images captured by the
   UVP5HD and processed by custom software. The scale bar indicates 2
   millimeters. Station number, image number for that cast, and depth
   at which the image was captured are also given in the image.

[Picheral2010] Picheral, M., Guidi, L., Stemmann, L., Karl, D.M.,
               Iddaoud, G., Gorsky, G., 2010. The Underwater Vision
               Profiler 5: An advanced instrument for high spatial
               resolution studies of particle size spectra and
               zooplankton. Limnol. Ocean. Methods 8, 462–473.


Sargassum
=========

PI
   * Dennis McGillicuddy


Overview
--------

Occupation of GO-SHIP lines A22 by R/V Thomas G. Thompson offered an
exceptional opportunity to sample the Great Atlantic Sargassum Belt
[Wang2019]. Satellite imagery indicates another significant bloom
began just before the cruise, with the abundance of Sargassum in
February of 2021 near the top of that observed in Februaries of the
last five years, second only to February 2018. Given the seasonality
of the phenomenon, Sargassum abundance was expected to increase during
the course of the cruise.

Recent evidence suggests a long-term shift in the elemental
stoichiometry of the seaweed (particularly N:P), which may reflect
changes in nutrient supply fueling these blooms [Lapointe_submitted].
Sargassum tissue samples in the high-abundance region of the tropical
and southern subtropical Atlantic are very few in number, with
opportunistic sampling by the R/V Thomas G. Thompson in August 2019
providing most of the measurements of which we are aware.

Clearly more observations are needed to test the hypothesis of a long-
term shift in N:P and its implications for nutrient supply and
Sargassum bloom dynamics. A22 extended into the high-abundance region,
and the core hydrographic and inorganic nutrient measurements will be
extremely valuable for interpreting satellite-based Sargassum
abundance. The critical need for opportunistic sampling is Sargassum
tissue.


Procedure
---------

Seaweed sampling was conducted by dipnet affixed to a standard
recovery pole. A standard sample is 30-40g, an amount that fits easily
into a quart-sized Ziploc bag. When sufficient biomass was available,
12 samples per station were collected, 6 dried and 6 frozen, each
comprised of triplicates for the two species S. fluitans and S. natans
which are easily distinguishable by their pods and leaves. In the
event that sufficient biomass was not available, dried samples were
prioritized.

Samples to be dried were rinsed with DI water, shaken dry, and placed
in drying oven on parchment paper with name of designated species and
station. Drying oven temperature were set between 55 and 65 C and
checked periodically with a thermometer inserted into top dryer vent.
Once sample was “bone dry” or crispy (typically 24-48 hours), sample
were placed in Ziploc bag and labeled with species, station location
collected, and date of collection.

Samples to be frozen were separated by species and placed in Ziploc
bags, labeled with a code referencing date, location, type. Excess
water was removed (with paper towel) prior to sealing bags and bags
were stored in a freezer and covered with a black blanket to keep
samples dark. Additional sample details were recorded on log sheets,
including date, time, location, GPS, etc.

[Lapointe_submitted] Lapointe, B. E., R. A. Brewton, L. W. Herren, M.
                     Wang, C. Hu, D. J. McGillicuddy, S. Lindell, F.
                     J. Hernandez, and P. L. Morton, submitted:
                     Nutrient content and stoichiometry of pelagic
                     Sargassum reflects increasing nitrogen
                     availability in the Atlantic Basin. Nature
                     Communications.

[Wang2019] Wang, M., C. Hu, B. B. Barnes, G. Mitchum, B. Lapointe, and
           J. P. Montoya, 2019: The great Atlantic Sargassum belt.
           Science, 365, 83-87.


Nitrate Isotopes \delta^15N AND \delta^18O
==========================================

PI:
   * Daniel Sigman (Princeton University)

Samplers:
   * Holly Olivarez

   * Maya Prabhakar

   * Victoria Schoenwald

   * Ali Siddiqui

Nitrate (NO_3^-) is the primary form of fixed nitrogen (N) in the sea
and an essential macronutrient, the supply of which can limit primary
production and carbon export from the surface ocean. The dual isotopes
of NO_3^- (\delta^15N and \delta^18O) record biogeochemical and
physical processes on different time scales. In general, nitrate
consuming processes tend to raise the \delta^15N and \delta^18O of
nitrate equally while nitrate producing processes tend to decouple the
dual isotopes. Since different processes leave different imprints on
the isotopic composition of nitrate, the dual isotopes can be used to
separate and quantify the impact of multiple N fluxes acting on the
nitrate pool.

Seawater samples for nitrate isotope analyses were collected from all
depths at about every two degrees of latitude. Two 30mL samples were
collected from each niskin bottle fired at depths shallower than 300
m. One 30mL sample was taken from all other depths. All bottles were
rinsed once with half their full volume before being filled with
seawater. The samples were stored onboard at -20°C in order to
preserve them for land based analysis.


Analysis
--------

The denitrifier method [Casciotti2002] [Sigman2001] will be used to
analyze NO_3^-, \delta^15N, and \delta^18O. Briefly, this method
converts all NO_3 to nitrous oxide (N_2O) via denitrifying bacteria
before the sample is analyzed by an IRMS. Samples were collected at
stations 1, 11, 15, 22, 31, 41, 43, 46, 50, 55, 61, 67, 73, 77, 83,
and 90.


INT (Microbial Respiration)
===========================

PI
   * Craig Carlson (UCSB)

Technician
   * Chance English

Analysts
   * Chance English

Support
   NSF


Motivation
----------

Heterotrophic Respiration is the fundamental process by which
organisms obtain energy from organic matter and at the ecosystem level
represents the largest sink for organic matter in the ocean
[DelGiorgio2005]. Understanding the magnitude and variability of
microbial respiration is critical for the understanding the metabolic
balance of the ocean and the efficiency at which carbon is stored in
the ocean. Measurements for respiration are rarely performed due to
constraints in methodology and feasibility and thus respiration
remains one of the least constrained parameters in contemporary
oceanography [Robinson2019]. However, recent advances in methodology
via the Iodo-nitro-tetrazolium (INT) reduction assay have improved the
ability to measure microbial respiration in aquatic environments
[García-Martín2019]. During this cruise, community and size-
fractionated respiration rates were determined using the INT reduction
method described below.


Sampling
--------

*In-Vivo Iodo-Nitro-Tetrazolium (INT) Reduction Assay*

This method is based on the reduction of INT, a water soluble,
membrane permeable salt which passively penetrates into the cell, by
dehydrogenase enzymes in the electron transport system forming
insoluble formazan crystals (INT-f) [Martínez-García2009]. The in-vivo
method is based on a variation of the in-vitro method described by
[Packard1996]. Whole seawater was collected from 5m using the ship’s
underway seawater system at 30 stations across the transect. Five 250
ml polycarbonate bottles were rinsed with sample water and filled, two
of which were immediately killed with 0.2 filtered formalin (2% v/v
final concentration) and used as a control. The remaining 3 bottles
were inoculated with 8mM INT solution to a final concentration of 0.2
mM. Samples were incubated within 1 degree of in situ temperature for
2-2.5 hours and subsequently fixed with formalin. Because the INT-f is
formed internally, cells can be size-fractionated post-incubation and
the INT-reduction rate determined for different size classes,
specifically bacterial (0.2-0.8µm) and non-bacterial (>0.8µm). During
A22 samples were filtered sequentially through a 0.8 and 0.2 µm
polycarbonate filter which were then stored in 2ml sterile cryovials
at -20ºC until further analysis. Samples from A22 were stored on board
until being shipped back to an in-shore laboratory at the University
of California, Santa Barbara. The method uses the spectrophotometric
absorption of the INT-f at 485 nm to determine the rate at which the
insoluble crystals are formed inside the cell membranes. Absorbance of
each sample will be determined by incubating the filters in 1 mL of
1-propanol, followed by sonication and centrifugation. The
concentration of the INT-f in solution is calculated from its
absorbance by applying a standard curve previously determined using
twelve different concentrations of stock INT-f dissolved in pure
1-propanol.


Stations sampled
^^^^^^^^^^^^^^^^

+------------------+------------------+------------------+------------------+------------------+------------------+
| 2                | 10               | 14               | 18               | 20               | 22               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 32               | 34               | 38               | 41               | 42               | 44               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 48               | 50               | 52               | 54               | 58               | 62               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 64               | 68               | 70               | 72               | 73               | 74               |
+------------------+------------------+------------------+------------------+------------------+------------------+
| 76               | 78               | 80               | 84               | 86               | 88               |
+------------------+------------------+------------------+------------------+------------------+------------------+

[DelGiorgio2005] Del Giorgio, P. A., & Williams, P. J. leB (Eds.).
                 (2005). Respiration in aquatic ecosystems. Oxford
                 University Press.

[García-Martín2019] García-Martín, E. E., Aranguren-Gassis, M., Karl,
                    D. M., Martínez-García, S., Robinson, C., Serret,
                    P., & Teira, E. (2019). Validation of the in vivo
                    Iodo-Nitro-Tetrazolium (INT) Salt Reduction Method
                    as a Proxy for Plankton Respiration. Frontiers in
                    Marine Science, 6, 220.
                    https://doi.org/10.3389/fmars.2019.00220

[Martínez-García2009] Martínez-García, S., Fernández, E., Aranguren-
                      Gassis, M., & Teira, E. (2009). In vivo electron
                      transport system activity: A method to estimate
                      respiration in natural marine microbial
                      planktonic communities: Estimating in vivo ETS
                      activity rates. Limnology and Oceanography:
                      Methods, 7(6), 459–469.
                      https://doi.org/10.4319/lom.2009.7.459

[Packard1996] Packard, T. T., Berdalet, E., Blasco, D., Roy, S. O.,
              St-Amand, L., Lagacé, B., Lee, K., & Gagnó, J.-P.
              (1996). Oxygen consumption in the marine bacterium
              Pseudomonas nautica predicted from ETS activity and
              bisubstrate enzyme kinetics. Journal of Plankton
              Research, 18(10), 1819–1835.
              https://doi.org/10.1093/plankt/18.10.1819

[Robinson2019] Robinson, C. (2019). Microbial Respiration, the Engine
               of Ocean Deoxygenation. Frontiers in Marine Science, 5,
               533. https://doi.org/10.3389/fmars.2018.00533


Oxygen Stable Isotope Record (\delta^18O)
=========================================

PI
   * Kaustubh Thirumalai

Cruise Participant
   * Maya Prabhakar


Intent
------

The creation of a seawater \delta^18O record for studying recent and
modern planktic foraminiferal \delta^18O in the N. Atlantic to
reconstruct past climate and create modern calibrations.


Sampling
--------

At least two 5mL samples of water were collected at every station.
Every station was sampled at 5m (surface, mixed layer) and at the
chlorophyll maximum, which varies at each station. Opportunistic third
and fourth samples were taken when Stephanie O’Daly’s underwater
vision profiler photographs showed foraminifera at those depths at
nearby stations. Samples were taken at the end of sampling by running
vials under a weak stream from the bottle spigot until air bubbles
were absent. The sample was then capped and inverted to check for air
bubbles. Some samples were lost early in the cruise due to
inexperience sampling from the bottles, resulting in air bubbles,
causing the additional step of an inversion to be added. Samples were
then parafilmed to prevent atmosphere and sample interaction. If, upon
inspection, samples were deemed improperly parafilmed, additional
parafilm was used to ensure a seal. Samples were labeled and stored in
a temperature-controlled room. Depth, longitude, latitude, bottle
number, date, sampler, and notes were recorded during sampling.


Processing
----------

Samples will be processed on a Picarro isotopic water analyzer at the
St. Petersburg Coastal and Marine Science Center. Methods and data
will be published within the next three years.


Acknowledgements
----------------

I would like to acknowledge the help of another student, Holly
Olivarez, in sampling when I was unable.


Student Statements
==================

U.S. GO-SHIP thanks all of the students who participated on the cruise
for their important contribution to collection of this essential
global ocean data set, used as the benchmark for accuracy of all other
deep ocean observing systems. The training opportunity for students
and leadership is an important part of US GO-SHIP’s mission. We are
committed to do so in a fair, cooperative and professional
environment, ensuring an inclusive, safe and productive climate at
sea. We thank the students for their honest reflections on their
experiences that are included in this section. We have reached out to
those who expressed concerns and are taking issues raised seriously,
by working to address and prevent these issues from occurring in the
future. We also thank them for their feedback in the anonymous post-
cruise survey, which we are using to continue to improve our program.
This will include ongoing education for all members of our community
to create a more inclusive environment.


Lillian Henderson
-----------------

As primarily a marine organic geochemist, the research I do on a daily
basis involves intensive lab work and wet chemistry in order to
isolate individual compounds for stable carbon and nitrogen isotope
analysis. Because of the time required to prepare each sample, I
typically work with relatively small datasets/sample sizes. In
contrast, the CFC work I was able to do on the GO-SHIP A22
hydrographic cruise involves very little sample preparation, allowing
for much larger collections of data. These larger datasets provide
better understanding of the global ocean circulation patterns. Being a
part of this cruise provided me an opportunity to learn a new sampling
method and analytical technique that I would not have been exposed to
otherwise. I learned about the analytical system used to measure
CFC/SF6/N2O concentrations and how these data are used. I had a great
time getting to know everyone, and I hope to work on another GO-SHIP
cruise in the future!


Holly Olivarez
--------------

*Environmental Studies Program and the Institute of Arctic and Alpine
Research (INSTAAR)*

As a graduate student who statistically models the variability of air-
sea CO_2 flux using in situ surface ocean p|CO2| observations, I am
very grateful for the experience and perspective I gained from being
part of the A22 hydrographic research cruise. From the science to the
people on the ship, being here has helped me grow as a human and as a
scientist. Even though I have worked in an observational environment
before, it was not related to oceanography. The ocean knows no borders
and sharing passion and curiosity for this critical system on Earth
with fellow scientists and ship crewmates was priceless. I learned of
the many ways one small, overlooked detail (either due to inexperience
or fatigue) can disrupt or invalidate a rosette full of freshly
collected seawater, or how moving a cast time to accommodate dinner
for samplers impacts the ship crew, too. I learned about folks who
care so deeply about “good” data that they devote their career to the
science of taking accurate and precise measurements.

I also learned that those who have been at sea for much of their
career, either as a scientist or as a ship crewmate, can teach me more
than I’ve learned in any classroom or textbook. I suppose the real
challenge then becomes finding the intersection between those who
teach in a classroom, who lay the groundwork for future real-world
application, and those who teach us in the moment as we are doing the
actual science.

My PhD research is based on the simulated Earth system but grounded in
real world observations. Without observations, scientists’ simulations
of the Earth system would be purely theoretical. This experience has
given me the perspective and recognition of real-world observations as
the foundation of what I do. This is something I will not forget as I
forge ahead in my career. Thank you to all involved in the GO-SHIP
project and thank you for the opportunity to be a part of it.


Maya Prabhakar
--------------

As a paleoclimate student with a background in geology, moving my
fieldwork from land to sea has been a sizable shift. The Thompson, and
GO-SHIP, is a great introduction to ocean research. I attended as a
CTD watch-stander to better understand how CTD data is collected since
I use it often in my research. I have thoroughly met my goal. We, the
attending students, have prepped casts for deployment and for
sampling, giving us a good understanding of the mechanical workings of
the rosette. Monitoring casts has allowed us to see the change in
station oceanography in real time and provided good conversations. The
limitations of the subsequent data and uncertainties are better
categorized in my head when thinking about the datasets I use from GO-
SHIP and similar projects. Our graduate curriculum is light in
physical oceanography, so being able to ask questions consistently for
a month provided a useful learning experience. I am primarily
interested in noting the data from the Gulf Stream because I focus on
the Arctic and the Fram Strait, which are heavily influenced by the
Gulf Stream. This cruise has brought about several questions related
to my field of study which I plan to explore when I am.

I have been consistently fortunate to work for, and with, numerous
women and racial minorities during school. This is a strong contrast
to the ship. I am still fortunate to be working under two amazing
women acting as chief scientists during this leg and I have loved
being able to ask questions and discuss science with them and the
other women on board, but I have run into multiple occasions during
this leg where I have been patronized consistently by a handful of
people, often on topics I have training and experience in. It has
reminded me to be grateful as a racial minority and a woman to work in
the labs I do and collaborate with the people I currently work with.
It is an unfortunate epidemic in the whole of science, but I note it
as a distinct failure of the GO-SHIP cruise.

Being able to actively learn and bring a background of geology to the
cruise has been a lot of fun and a welcome change from the zoom
learning of a covid-19 world. I have gained numerous skills and
insights that will help me navigate future fieldwork and create new
discussions in my lab. I look forward to publishing the geochemical
data from this cruise.


Victoria Schoenwald
-------------------

The A22 leg of this year’s GO-SHIP cruise was my first glance into
what observational oceanography is all about. I participated as a CTD
Watch Stander on the night shift for 30 days which involved long hours
of watching the CTD rise and fall into the water while monitoring
screens taking real time data from temperature to voltage spikes from
the UVP. Being a part of a modelling lab as a graduate student at the
UM RSMAS, I would not have had the opportunity to go to sea if not for
programs like GO-SHIP. I am grateful that all of the scientists on
board were happy to allow new students to become part of their
research. When I first decided to pursue a career in oceanography, I
was excited about discovering the way the ocean, atmosphere, and land
interreact with one another. I later realized that my interests
aligned well with global climate modelling and field work would not be
part of my Ph.D. experience. From the start I knew that I would want
to get back into field work some way or another so when I discovered
there were openings to come on the A22 leg I was very excited.

Back in Miami I was researching sea level rise and coastal flooding
using global data sets and climate models. Being on the CTD team
therefore allowed me to see where some of my data is coming from and
how the ocean off of the East Coast of the U.S. has been changing over
the years. Besides the knowledge I learned from the science team one
of the most rewarding parts of the cruise was getting to know the
crew. I enjoyed hearing their stories about travelling, life at sea
and gained perspective on careers that I previously knew nothing
about. Getting to know more people who love the ocean as much as I do
has made this month an unforgettable one. This experience has reminded
me why I chose to research the ocean in the first place, and I hope to
have the chance to participate in more research cruises in the future.


Ali Siddiqui
------------

To whoever reads this in 10 years

Hi there!

I was a CTD watchstander and the LADCP operator for the A22 2021 GO-
SHIP cruise.

If you’re a student reading this, wondering what a watchstander or an
LADCP operator experiences in a GO-SHIP cruise, I might not be able to
do justice in this short statement. If you’re a PI reading this, and
wondering if your students should take part in a GO-SHIP cruise, this
statement would only offer a fleeting peak into the experiences of
potential students. If you’re just someone browsing through student
statements, I hope this one offers you something of value about the
lives of GO-SHIP participants. I guess the only person who really
needs to read this is Mike Kovatch who’s wonderful job gives him the
pleasure to make cruise reports which contain the tired musings of
departing students. So, let me be terse.

As someone whose research involves modeling the ocean using computers,
it’s very easy for me to forget what the real ocean looks like. The
ocean exists in the virtual world with smooth data and exact floating
points accurate to the precision of the computer. What the CTD
watchstanding taught me was how the ocean really looks like. In
person. Or in water ? It taught me the importance of taking accurate,
reliable and long-term measurements of the ocean using the CTD. It is
very easy to sit in a lab and complain about missing data in the
ocean. What this cruise has taught me is the value of recording data
during each CTD cast and the amount of hard work and labor that goes
into procuring a single vertical profile in the deep ocean.
Undoubtedly, I’m going to be a better oceanographer after this cruise,
or atleast a more informed one.

As for the LADCP, even though I had read up about the theory of the
Acoustic Doppler and its functionality, it was an extremely
enlightening experience to operate the instrument on my own.
Admittedly, I was very nervous in the beginning but things got better
as we performed regular deployments. Processing and understanding the
ADCP data was another trick of the trade that I got to learn as we
made our way from the Caribbean to the familiar shores of Woods Hole.
Hopefully, I will have more opportunities in the future to operate the
LADCP.

There are a few of lessons that I will take away from my experience. I
hope when someone reads this, they would find them helpful too. The
first is about the importance of the ship crew. Without them, no
science would ever be done. On the R/V Thompson, the crew was the star
of the show in my eyes. They would help us with deployments, carry out
maintenance on the ship, feed us, navigate us, and most importantly
give us a glimpse into the lives of people who spend half their lives
on the sea. If any person in a position of leadership is reading this,
I want to acknowledge how important the crew of the R/V TGT was to us
and commend them on a brilliant job they did to help us do our
science. Another lesson was about the importance of staying patient on
the ship. Taking measurements in the sea can get monotonic after a
while, and people tend to slack off and become impatient with the
process. I realized how important it was to carefully go through each
and every step in our deployments, right from preparing and keeping
track of log sheets to preparing the rosette for each cast, all the
way up to firing bottles at the right depth and eventual recovery and
sampling. Even though we get trained in all these exercises, it is
interesting to see how much one can learn about an activity each time
you repeat it. This brings me to the final lesson worth typing in this
statement, which is that of mental well being at sea. The ship is a
small space to be in for a month with a bunch of people who you’ve
never met. It is very easy to get cranky around mid-way through the
cruise. However, it really helps if you have something to occupy
yourself with on your time off. Reading books, playing chess or catan
and even darts, personal writing, admiring the ocean and the stars on
the hammock at the bow, were some of the things that helped me keep
myself cheerful. Obviously, this was on top of making friends with
some really amazing people on the ship.

If that doesn’t give much glimpse into the mind of a watchstander,
then maybe the knowledge that most of us were even dreaming of the CTD
and muttering, “Roger that, we are ready to deploy”, should tell you
all about the experience.

With hope,

Ali Siddiqui
