                               CRUISE REPORT

                                HUDSON 93019

                                LABRADOR SEA

                              WOCE LINE AR7/W

                             JUNE 17 - 28, 1993

A. CRUISE NARRATIVE

1. Highlights

 Cruise Designation: 18HU93019/1
 Ship:               C.S.S. Hudson
 Agency:             Bedford Institute of Oceanography
                     Box 1006
                     Dartmouth N.S. B2Y 4A2, Canada
 Chief Scientist:    John R.N. Lazier
 Ports of call:      Sydney N.S. to Dartmouth N.S.
 Dates:              June 17 - 28, 1993

2. Cruise Summary

Cruise Track:

The CTD/rosette station positions are shown in Fig. 1. Heavy ice over the
Greenland continental shelf prevented completion of three proposed stations
at the eastern end of the line.

[Image]

Figure 1. Stations along WOCE line AR7/W occupied during June 1993.

Sampling Accomplished:

The Seabird CTD acquired temperature, salinity and oxygen profiles. Rosette
water samples were obtained for analyses of salinity, oxygen, nutrients,
CFC-12, CFC-12, CFC-113, total carbonate, alkalinity, halocarbons, tritium
and helium.

3. Principal Investigators

Name                  Responsibility                  Affiliation

John Lazier           CTD, salinity                   BIO
Bob Gershey           CFC, O2, alkalinity, CO2,       BDR
                      nutrients
Katarina Abrahamsson  Halocarbons                     U of G
Lina Kohandoust       Tritium, Helium                 LDEO (Peter Schlosser)

Institute Abbreviations and Addresses

BIO     Bedford Institute of Oceanography
        Box 1006
        Dartmouth, N.S. B2Y 4A2, Canada
BDR     BDR Research Ltd.
        Box 652, Sta. 'M'
        Halifax, N.S. B3J-2T3, Canada
U of G  University of Göteborg
        Göteborg, Sweden
LDEO    Lamont-Doherty Earth Observatory of Columbia University,
        Palisades, NY, 10964, USA

Electronic Addresses

J. Lazier       j_lazier@bionet.bio.dfo.ca
R. Gershey      rgershey@fox.nstn.ns.ca
K. Abrahamsson  katarina@amc.chalmers.se
L. Kohandoust   lina@lamont.ldeo.columbia.edu

4. Scientific Program

One of the primary aims of the annual occupation of the AR7/W line is to
monitor the properties of the Labrador Sea Water (LSW) which is renewed in
severe winters by deep convection. Our 1993 observations indicate that
convection was very active during the 1992-93 winter and that the LSW is now
colder and denser than ever previously recorded.

To illustrate, the distribution of sigma 1.5 across the section is given in
Fig. 2 and some curves of potential temperature vs sigma 1.5 for the central
Labrador Sea are compared in Fig. 3 with other years. In the section the LSW
is identified by the layer of very low vertical gradient in the central
region (stations 14 to 22) between s1.5= 34.68 and 34.70. Over the
continental slopes (stations 10-13 and 23-26) the gradient between these two
density surfaces is about five times greater than in the central region.
This results in a large along isopycnal gradient in potential vorticity
which restricts along isopycnal exchange. The result is that the central low
gradient region tends to be isolated from the water of similar density over
the continental slopes.

[Image]

Figure 2. Section of potential density anomaly referenced to 1500 dbar (1.5)
along the WOCE AR7/W line in June 1993.

[Image]

Figure 3. Potential temperature vs. sigma-theta at a selection of stations
in the central Labrador Sea during 4 cruises; Erika Dan, March 1962; Hudson,
June 1990, June 1992 and June 1993.

Also, recent current meter observations have shown the existence of a strong
(0.2 m s-1) barotropic current over the Labrador slope but almost no current
(<0.01 m s-1) in the central region. Vorticity strongly confines the
barotropic flow to stay over the slope which further tends to isolate the
central region.

It appears that these features which limit mixing and advection between the
central region and the boundary flows help to preserve the properties of the
LSW through periods of weak convection in winter.

Some of the variation in the LSW properties over the years is shown in the
sigma 1.5 vs potential temperature curves in Fig. 3. The LSW in 1993 is
distinguished by the minimum temperature of 2.7 °C at st = 27.775 kg m-3. In
1990 this temperature mininmum was at 2.8 °C at 27.760 kg m-3 and in 1992 it
was somewhere between these two. The variation over these years indicates a
continual cooling and increase in density of the convected water mass. In
the curves for 1992 (Erika Dan cruise) the minimum is not so clear as in the
more recent data because the data were collected by widely spaced bottles
rather than continuous recording CTDs. But a minimum is apparent at about
3.3 °C at st » 27.765 kg m-3. Thus it appears that the density has stayed
roughly constant while the temperature of the water has decreased by 0.6 °C.
This decrease is attributable to the lower salinity water that now inhabits
the Labrador Sea as a result of the large influx of fresh water from the
Arctic in the late 1960s. Maintaining the nearly constant density of the
fresher convected water has required a lower temperature. Similar
observations from other years show however that there are slight variations
in the density of the LSW and that the density in 1993 is the greatest yet
observed.

5. Underway Measurements

At all times during the sampling program the position of the ship as
determined by the Global Positioning System was recorded. The depth sounder
was kept running between all CTD stations when ice and wave conditions
permitted. A hull mounted Acoustic Doppler Current Profiler (ADCP) was also
operated during the sampling program.

6. Major Problems and Goals not Achieved

Heavy ice over the Greenland shelf prevented occupation of the 3 easternmost
stations over the Greenland continental slope and shelf.

Collision between the ship and the rosette resulted in damage to the rosette
and sampling bottles at the end of the first cast on Station 13. This event
also made the salinity and oxygen channels on the CTD noisier, however, this
was repaired by carefully retying the water circulation tubes and electronic
cables.

7. Other Incidents of Note

An Acoustic Doppler Current Profiler was deployed over the Labrador Shelf as
part of the Bedford Institute's program to study the movement and stresses
of the drifting pack ice. This study is under the direction of Dr. Simon
Prinsenberg. The following report is by M. Scotney and A. Hartling of BIO.

Mooring No. 1133: A RD Instruments Self-Contained Acoustic Doppler Current
Profiler housed with in a Trawl Resistant Package was moored on June 19,
1993 at position 53 50.697 N and

56 03.145 W. The data from this instrument will enable the ice movement
above to be monitored for the winter of 93/94 as part of the Labrador Ice
Flux Study.

The package was moored in 86 meters of water using the new deployment frame.
The system was free fallen to the bottom without difficulty. Hand tension
was kept on the lowering rope during decent. The package dropped at a rate
of approximately 35 meters per minute. Since the acoustic release on the
lowering frame was fitted with a 6 degree tilt switch, it was confirmed
acoustically that the package was not tilted more than 6 degrees prior to
release.

The ADCP is set to start recording at 0100 hours on Nov.1, 1993. This will
allow sufficient battery capacity for data to be recorded until recovery
next year.

8. Cruise Participants

 Name                   Responsibility             Affiliation
 Abrahamsson, Katarina  Halocarbons                U of G
 Bellefontaine, Larry   CTD watchkeeper            BIO
 Carson, Bruce          CTD tech/watchkeeper/salts BIO
 Clement, Pierre        Nutrients                  BIO
 Ekdahl, Anja           Halocarbons                U of G
 Gershey, Robert        CFC, Alk., Carb.           BDR
 Gohlin, Karin          Halocarbons                U of G
 Griffies, Stephen      CTD watchkeeper            GFDL
 Hartling, Bert         Mooring/ CTD watchkeeper   BIO
 Hingston, Michael      CFC, Alk., Carb.           BDR
 Hufford, Gwyneth       CTD watchkeeper            DEAPS
 Kohandoust, Lena       Tritium/Helium             LDEO
 Lazier, John           Chief Scientist            BIO
 Moffatt, John          Oxygens                    BIO
 O'Neill, John          Computers/software         BIO
 Rhines, Peter          Advisor/CTD watchkeeper    U of W
 Ross, Charlie          Co-chief scientist         BIO
 Scotney, Murray        Mooring/CTD watchkeeper    BIO
 Swim, David            CTD watchkeeper            BIO
 Zemlyak, Frank         CFC, Alk., Carb.           BIO

Institute Abbreviations and Addresses

BIO     Bedford Institute of Oceanography
        Box 1006, Dartmouth, N.S. B2Y 4A2, Canada
        BDR Research Ltd.
BDR     Box 652, Sta. 'M'
        Halifax, N.S. B3J 2T3, Canada
U of G  University of Göteborg, Göteborg, Sweden
        School of Oceanography, WB-10
U of W  University of Washington
        Seattle, WA, 98195, USA
        Lamont-Doherty Earth Observatory
LDEO    of Columbia University,
        Palisades, NY, 10964, USA
        Geophysical Fluid Dynamics Laboratory
GFDL    Princeton University
        Princeton, NJ, USA
DEAPS   Dept. of Earth, Atmos. and Planetary Sciences
        Massachusetts Institute of Technology, Cambridge USA

Electronic Addresses

J. Lazier       j_lazier@bionet.bio.dfo.ca
R. Gershey      rgershey@fox.nstn.ns.ca
K. Abrahamsson  katarina@amc.chalmers.se
L. Kohandoust   lina@lamont.ldeo.columbia.edu
P. Rhines       rhines@ocean.washington.edu
S. Griffies     smg@gfdl.gov
G. Hufford      gwyneth@pimms.mit.edu

B. DESCRIPTION OF MEASUREMENT TECHNIQUES AND CALIBRATIONS

1.	CTD Operation                                         
	B.D. Carson (BIO)

The Seabird CTD (OC #1) was used on this cruise and once again performed
well from a maintenance standpoint. It seems as though the data are a little
more noisy this time and we had a little trouble with the pump. After the
unit received a bump during recovery on station 13 a few of the 8 litre
sampler bottles were damaged and the tube which connects the top of the TC
duct to the pump, via the O2 sensor was jarred loose. The tube was replaced
and made a little more secure after station 14 and was fine for the rest of
the trip. The pump stopped working a little later and was replaced by a new
one and the O2 snesor was also replaced at this time although it has not
been determined if that was neccessary. The old pump is intermittent and
will be checked more closely in the lab at BIO.

2.	Bottle Salinity                                         
	C.K. Ross (BIO)

The Guildline AUTOSAL 8400 salinometer (Autosal #3) worked well and was very
stable once the lab temperature was stabilized. All salinity water samples
were analyzed within 1-2 days of sampling. Duplicate samples were drawn from
one or two rosette bottles on each station. Statistics of the absolute
difference between duplicates are below:

Number of Points = 38

Median = 0.0004

Mean = 0.0011

Minimum = 0

Maximim = 0.0063

Standard Deviation = 0.0014

Throughout the mission, IAPSO standard batch number P117 seawater was used
as the reference seawater.

An attempt at identifying suspecious bottle salinity values was made using
the statistics of the differences between CTD salinity and bottle salinity.
By identifying the 25 and 75 percentile differences (denoted by Q1 and Q3),
we identified all differences outside of the following limits:

difference < Q1 - 1.5*(Q3 - Q1)

difference > Q3 + 1.5*(Q3 - Q1)

All bottles associated with these samples were flagged as 'leaking'. All
associated salinity samples were flagged as 'questionable' or 'bad'. The
'bad' flag was subjectively assigned depending on the number of times a
particular bottle was identified in this manner.

3.	CTD Data Quality                  
	C.K. Ross and Anthony W. Isenor (BIO)

The Sea-Bird CTD model SBE 9plus (S/N 9P5676-0248) was paired with a 22
bottle rosette to allow calibration of the sensors as well as collection of
water samples for other chemical determinations. The data were logged using
SEASOFT software using the calibration data for the sensors when the
instrument was delivered in February, 1992. The sensors have been calibrated
since then but the figures presented are referenced to the original
calibrations.

The pressure sensor (S/N 48361) was not compared at depth. The data were
logged before the instrument entered the water to allow the determination of
the pressure offset at 0 dbars. These have not yet been examined.

The temperature sensor (S/N 031247) was compared to a suite of six
electronic digital reversing thermometers. Initially, thermometer
calibration data from February 1991 were used to correct the thermometer
readings. However, subsequent examination of the corrected temperatures
using post-cruise calibration data from March 1994 showed improved
differences (thermometer - CTD) statistics, namely a more peaked
distribution and smaller difference from CTD.

The thermometer data were corrected using the March 1994 thermometer
calibration data. The difference (thermometer - CTD) was then computed and
the values sorted and plotted. The resulting curve showed that thermometer
T352 gave consistently large differences as compared to the CTD. This
thermometer was removed from the analysis and the resulting difference curve
replotted. The curve showed a low slope region below the zero difference,
indicating a high CTD temperature compared to the thermometers. After
removing the outliers beyond the limit of median 1.5*IQR (interquartile
range), the median value of the resulting set of differences was determined
to be -0.002 C. The -0.002 value was used as the CTD temperature
calibration.

The salinity determined from the CTD conductivity sensor (S/N 040954) was
compared to the salinity of the water sample. For the 38 occurrences of
CTD-bottle greater than 0.01, 13 were due to bottle BO11, 7 due to bottle
OC7, 5 due to bottle OC6, 3 due to bottle OC1, 2 due to bottle OC3 and the
other bottles having 1 or fewer. For the 12 occurrences of CTD-bottle less
than -0.02, there were 2 each for bottles BO11, OC17, OC1 and BO17. It seems
apparent that some bottles (in particular bottle BO11) were misfiring or
leaking. More attention will have to be paid to this possibility.

The differences of CTD and bottle salinities were accepted if within the
range -.01 to .002. This reduced the number of comparisons from 363 to 297.
The variance of these data was .00000437. There appeared to be a possibility
of a temperature dependence. A linear regression was fit:

DS(se=.0020) = -0.00036(se=7.22E-5)*T-0.00425

r2=0.077

One could also fit the differences to salinity:

DSse=0.0021) = -0.00058(se=.000185)S+0.0148

r2=0.0318

If one removes the linear regression in temperature there is no apparent
dependence of the salinity difference on pressure or time.

These data indicate that the CTD is reading low by 0.004 compared to the
most recent laboratory calibration of 0.003 low. The standard deviation of
differences is slightly greater than 0.002.

The equations used to convert CTD signals to engineering units were as
follows:

Conductivity Sensor 040954 (all stations)

    Conductivity = (afm + bf2 + c + dt)/[10(19.57(108)p)]

    where f is the frequency

               t is the temperature

               p is the pressure in dbars

               a = 1.01513041E5

               b = 5.69078601E1

               c = 4.20143902

               d = 2.42081062E4

               m = 4.4

Temperature Sensor 031247 (All stations)

    Temperature = 1/{a + b[ln(fo/f)] + c[ln2[fo/f] + d[ln3(fo/f)]} 273.15

    where ln indicates a natural logrithim

                f is the frequency

                a = 3.68701496E3

                b = 6.01256466E4

                c = 1.53681774E5

                d = 2.54555248E6

                fo = 6590.790

Pressure Sensor 48361 (All stations)

    pressure = c (1  To2/T2) (1  d[1  To2/T2])

    where      T is the pressure period

               c = c1 + c2 U + c3 U2

               d = d1 + d2 U

               To = T1 + T2 U + T3 U2 + T4 U3 + T5 U4

               U is the temperature

               c1 = 2.651490E+4

               c2 = 1.537220E1

               c3 = 8.182160E3

               d1 = 3.319500E2

               d2 = 0.0

               T1 = 3.057779E+1

               T2 = 2.025480E4

               T3 = 4.254880E6

               T4 = 1.790020E9

               T5 = 0

Oxygen Sensor 130284 (Stations 1 to 19)

    oxygen = A B C

    where      A = {Soc [oc + Tau d(oc)/dt] + Boc}

               oc is the current from the oxygen sensor

               d(oc)/dt is the time derivative of oc

               Soc = 2.5328

               Tau = 2.0

               Boc = 0.0322

               B = OXYSAT(t,s)

               t is temperature

               s is salinity

               C = e{tcor [T + wt (ToT)] + pcor p}

               e is natural log base

               tcor = 3.3E2

               pcor = 1.5E4

               p is the pressure

               wt = 0.670

               To oxygen sensor internal temperature

               T is the water temperature, where T = kv + c

               k = 8.9625

               c = 6.9161

               v is the oxygen temperature sensor voltage signal

Oxygen Sensor 130287 (Stations 20 to 26)

    oxygen = A B C

    where      A = {Soc [oc + Tau d(oc)/dt] + Boc}

               oc is the current from the oxygen sensor

               d(oc)/dt is the time derivative of oc

               Soc = 1.9222

               Tau = 2.0

               Boc = 0.0106

               B = OXYSAT(t,s)

               t is temperature

               s is salinity

               C = e{tcor [T + wt (ToT)] + pcor p}

               e is natural log base

               tcor = 3.3E2

               pcor = 1.5E4

               p is the pressure

               wt = 0.670

               To oxygen sensor internal temperature

               T is the water temperature, where T = kv + c

               k = 8.9655

               c = 6.9100

               v is the oxygen temperature sensor voltage signal

The final CTD temperature calibration was:

  T = T  0.002

where T is the temperature.

The final CTD salinity calibration was:

  S = S + 0.0052

where S is the salinity.

The final CTD oxygen calibration is discussed in detail in Appendix A.

4.	Oxygens                            
	J. Moffatt (BIO) and C.K. Ross (BIO)

a. Description of Equipment and Technique

The automated procedure to follow is based on the method developed by the
Physical and Chemical Services Branch (PCS) of the Bedford Institute of
Oceanography (BIO) (Levy et al. 1977).

The PCS procedure is a modified Winkler titration from Carritt and Carpenter
(1966), using a whole bottle titration. In this method there is no starch
indicator and a wetting agent (Wetting Agent A, BDH) is introduced to reduce
bubble formation. The full description of the system and method can be found
in Jones, et al. (1992).

In summary the automated titration system consists of an IBM PC linked to a
Brinkmann PC800 colorimeter and a Metrohm 655 Multi-Dosimat Automatic
Titrator. The PC talks to the peripherals through a Data Translation, DT2806
and three Data Translation DTX350s.

b. Sampling Procedure and Data Processing Technique

The sampling bottles are 125ml Iodine flasks with custom ground stoppers
(Levy et al. 1977). The flasks volumes are determined gravimetrically. The
matched flasks and stoppers are etched with identification numbers and
entered into the oxygen program database.

For this cruise 8 litre Niskin bottles were used to obtain the original
sample. Then, the oxygen subsamples are drawn through the bottles spigot
with a latex or silicone tube attached so as to introduce the water to the
bottom of the flask. Once the flow is started the flask is inverted to
ensure that there is no air trapped in the tube, then the tube partially
pinched to reduce the flow rate and the flask reoriented and filled to
overflowing. The flow is allowed to continue until at least two to three
volumes have run through then the flask slowly retracted with continuous low
flow to ensure that no air gets trapped in the flask. The flask is then
brought to the reagent station and one ml of the Alkaline Iodide and
Manganous Chloride Reagents are added and the stoppers carefully inserted,
again ensuring that no air gets into the flasks. The flasks are shaken then
carried to the lab for analysis.

c. Replicate analysis

A total of 428 seawater samples were analyzed for dissolved. Included in
these samples were a total of 45 duplicate samples. Approximately 1-2
replicates were taken at each station to monitor precision which can be
affected by flaws in sampling or titration.

A duplicate oxygen sample is drawn from one of the rosette bottles on every
cast. Statistics related to the difference in duplicate values was
determined using the absolute value of the difference. In total, 45
duplicate samples were drawn. Of these samples five (sample numbers 126062,
126149 [triplicate], 126219 and 126303) did not have a duplicate because one
or both values were missing or bad.

Number of valid duplicates = 41

Median of [(absolute difference/sample mean concentration) * 100%] = 0.31 %

Statistic                      Value (ml/l)            Value (moles/kg)

Minimum                              0                         0

Maximum                            1.274                     55.4

Mean                               0.081                      3.5

Median                             0.022                      1.0

Standard Deviation                 0.221                      9.6

Cumulative Frequency      Oxygen Difference          Oxygen Difference
                                  (ml/l)                  (moles/kg)

          50 %                     0.022                      1.0

          68 %                     0.030                      1.3

          95 %                     0.504                      21.9

5.	Computer                                               
	J. O'Neill (BIO)

The PC-486 Seabird CTD computer and software ran with minor modifications.
All 25 stations were processed in about 48% of real time which included
conversion to archive ODF-ASCII format and (new to the PC system) generation
of IGOSS significant points summary file.

The shipboard-resident MicroVax II was used to log continuous NMEA_NAV
format from the Trimble GPS navigation receiver. These data were processed
in real-time to distribute current positional information throughout the
ship.

A considerable amount of available CPU on the MicroVax was used to generate
post-acquisition graphics products, including sections derived from the CTD
casts and bottle sampled data. In addition an evaluation of the oxygen
sensor data was carried out using graphics and statistical modules of the
OCEANS/PIPE system.

Backup of CTD and NMEA data were completed in triplicate to Exabyte streamer
tapes (044374-044376).

6.	Nutrients                          
	P. Clement (BIO) and C.K. Ross (BIO)

Samples were analyzed for silicate, phosphate, and total nitrate (nitrate
plus nitrite) using an AutoAnalyzer-II using a modified version of
Technicons original chemistries. Washwater was 33 ppt (w/v) NaCl and no salt
correction was made.

Samples were collected in duplicate from the rosette bottles into 30 ml acid
washed high density polyethylene screw-capped bottles. These were
refrigerated until analysis, typically within 12 hours of collection. The
water samples were transferred to 7 ml cups for analysis with the
AutoAnalyzer.

Five mixed standards were run at the beginning and end of each run, with
"check standards" interspersed every sixteen sample cups. Each batch of
mixed standards are tested against Sagami CSK standards for nitrate and
silicate before use.

Precision is a measure of the variability of individual measurements and in
the following analysis two categories of precision are determined; field and
analytical precision. Analytical precision is based on the pooled estimate
of the standard deviation of the check standards over the course of a
complete autoanalyzer run and is a measure of the greatest precision
possible for a particular analysis. Field precision is based on the analysis
of two or more water samples taken from a single Niskin sampling bottle and
has an added component of variance due to subsampling, storage and natural
sample variability.

Both categories of precision are determined by computing the variance, , of
each replicate set, where i is the index of the replicate set. In the case
of analytical (field) precision, a replicate set consists of all the check
standards (duplicate samples). Given p replicate sets and n samples within
any replicate set, the mean standard deviation, , is determined from

The precison expressed in percent is based on the mean concentration, M, of
the check standards (analytical precision) or water samples (field
precision) and is given by

The following table indicates the analytical and field precision obtained
for this cruise.

                                Silicate    Phosphate     NO2+NO3

Number of Samples                 762          762          760

Number of Duplicates              381          381          381

Mean concentration (              9.27         0.94        13.21
moles/kg)

Field Precision ( moles/kg)       0.08         0.02         0.10

Field Precision (%)              0.9 %        2.1 %        0.8 %

Analytical Precision (           0.298        0.018        0.171
moles/kg)

Analytical Precision (%)         0.88 %       1.38 %       1.02 %

Detection Limit ( moles/kg)      0.187        0.056        0.101

The laboratory temperature during all analyses was between 21 and 23 °C.

The conversion to mass units for the analytical precision and detection
limits used a standard density corresponding to 33 ppt and 15C.

Duplicate samples were drawn from each rosette bottle for the determination
of silicate, phosphate and nitrate concentrations. The cumulative
frequencies of differences (expressed as a percent of measured
concentration) for each of the nutrients is:

  cum freq      silicate        phosphate        nitrate

    50%:         0.76%            0.94%           0.52%

    67%:         1.13%            1.58%           0.76%

    95%:         3.26%            7.03%           1.98%

The nutrient detection limits noted in the above table were applied to the
dataset. All values at or below the detection limits were set to zero.

7.	Halocarbons      
	R.M. Gershey (BDR), F. Zemlyak (BIO) and M.P. Hingston (BDR)

Objective:

1) To gather halocarbon concentration profiles using a purge-and-trap gas
chromatographic method. Analytes included are CFC-11, CFC-12, CFC-113, CCl4
(carbon tetrachloride) and CH3Cl3 (methyl chloroform).

Instrumentation for these measurements has been developed at the marine
chemistry division of the Bedford Institute of Oceanography under a PERD
funded program managed by E.P. Jones. The main objective of this program is
to collect data to be used in modelling the rate of large scale convective
transport of carbon dioxide gas from the atmosphere to the deep ocean. The
flux of atmospheric CO2 to the ocean can be estimated using measurements of
alkalinity, total CO2 and various transient tracers.

To increase thoughput, two halocarbon analysis systems were put to use
during this cruise. As a result our sampling density increased by a factor
of two over previous years and allowed us to analyze samples from all but
four stations. In addition, our collegues from the University of Goteborg
led by K. Abrahamsson were performing parallel analyses using similar
instrumentation. This will allow us to both compare our results and fill in
gaps in our data set.

Halocarbon data have been collected during four visits to WOCE line AR7/W
and surrounding areas in the Labrador Sea during 1986, 1990, 1991 and 1992.
The three main water masses in this area (NADW North Atlantic Deep Water,
LSW Labrador Sea Water and DSOW Denmark Straight Overflow Water) have easily
distinguished halocarbon concentrations. A halocarbon minimum characterizes
NADW identifying it as being the least recently ventilated water mass in the
area.

CFC-113 profiles have been successfully determined during this and the
previous cruise. The results show that this short time scale tracer (< 10
years) is useful for identifying recently ventilated surface waters (LSW and
DSOW) due the rapidly increasing source function for this compound.

It has long been believed that LSW is regularly subject to deep convection
to depths of 1500 to 2400 meters. Tracer data collected last year (1992)
showed a dramatic increase over the previous year's data, being a strong
indication that deep convection occurred to about 2100-2400 m. Contrary to
the expectation that the halocarbon levels we would measure during this
cruise would be equivalent to or higher than those collected in 1992,
preliminary analysis of the present data shows an apparent reduction of
halocarbon concentrations to 1991 levels. Excluding analytical difficulties
as an explanation for the disappearance of the tracers, horizontal advection
of water having a low tracer content is suggested. This also implies that
the extent of the ventilation event seen in 1992 may not have extended very
far to the north or south of the line. Unfortunately, there are at the
present time virtually no data with which to confirm this suspicion.

The following are the values of blank samples. All values are in pico
moles/kg.

CFC 11   0.007 p moles/kg

CFC 12           - 0.006 p moles/kg

CFC 113           0.003 p moles/kg

carbon tetrachloride    0.013 p moles/kg

methyl chloroform       0.005 p moles/kg

The following precisions apply to these data:

Freon 12     3.9%

Freon 11           4.3%

Freon 113       2.9%

Carbon Tetrachloride   3.1%

methyl chloroform      1.2%

Analytical accuracy relative to custom made gravimetric gas phase standards
(Brookhaven National Labs, N.Y.) is of the same order as the precision of
the analysis.

The following are the duplicate measurements used to compute the mean values
given in the SEA file.

Summary: Halocarbon tracers (CFC-11, CFC-12, CFC113, CCl4), methyl
chloroform and total inorganic carbon were measured at 21 stations on WOCE
line AR7/W. Comparison of halocarbon data collected during the last three
years provides evidence for ventilation of the upper 2500 m of the Labrador
Sea.

8.	Total Inorganic Carbon    
	R.M. Gershey (BDR), F. Zemlyak (BIO) and M.P. Hingston (BDR)

Objective:

1) To perform high-precision analyses for the measurement of total inorganic
carbon using a couloumetric method.

Instrumentation for these measurements has been developed at the marine
chemistry division of the Bedford Institute of Oceanography under a PERD
funded program managed by E.P. Jones. The main objective of this program is
to collect data to be used in modelling the rate of large scale convective
transport of carbon dioxide gas from the atmosphere to the deep ocean. The
flux of atmospheric CO2 to the ocean can be estimated using measurements of
alkalinity, total CO2 and various transient tracers.

Determination of total inorganic carbon (CT) was accomplished using a SOMMA
analyzer (developed at the University of Rhode Island) with coulometric
detection. Samples were processed from 20 of the 26 stations sampled. Based
on duplicate samples and analysis of carbon dioxide gas samples, a precision
of 1-1.5 parts per thousand was consistently achieved. A seawater reference
material obtained from the Scripps Institution was used to verify the
accuracy of the method. The analyses were performed using the standard
operating procedures specified by Dickson and Goyet (1991).

Summary: Measurements of Total Inorganic Carbon were made to the
WOCE-suggested precision of plus or minus 1 part per thousand.

9.	Biogenic Halocarbons      
	K. Abrahamsson, A. Anja and K. Golin (U of G)

Analyses of biogenic halocarbons were performed at 22 stations. Due to the
relatively long analysis time, emphasis was put on determinations of
compounds in the surface waters. The water was collected in 100 ml glass
syringes, and stored in coolers on deck. The compounds were degassed and
concentrated with a purge and trap techinque, and thereafter analysed by gas
chromatography with electron capture detection. The purge and trap system
has been developed in co-operation with Dr. E.P. Jones, Marine Chemistry
Division of the Bedford Institute of Oceanography. The technique enables us
to determine 19 individual fluorinated, chlorinated, brominated and iodated
compounds. Blanks were run continuously throughout the cruise and standards
were run every other day. Liquid standards were used for all compounds
except for the CFC's (Freon-12, Freon-11 and Freon-113) and
carbontetrachloride (CCl4).

This has been the first sea-going test for our newly developed system. The
automated sample handling and the increased extraction efficiency have
improved both precision and limits of quantification. The technique also
gives us the possibility to study the volatile methylhalides, which could
not be done with our former analytical method. An intercalibration was
performed between our system and those of the BIO for the CFC's and CCl4. It
will be possible to compare results from approximately 150 water samples.
The instruments were calibrated with the same gas standard.

We had hoped to collect micro-organisms in the upper 10 m of the water
column with a plankton net at near-shore stations, in order to study the
formation of halocarbons. However, the combination of bad weather, ice
conditions, along with the work load, precluded us from using the net more
than once. The sample showed increased concentrations of iodated compounds,
due to micro-organism activity.

10.	Vessel Mounted Acoustic Doppler Current Profiler      
	M. Scotney (BIO)

The VMADCP was set to profile at the beginning of the WOCE CTD line on June
19,1993 and continued to log data until June 26,1993. Logging was halted
once we entered the Straits of Belle Isle on our return trip to B.I.O.

The instrument was configured to measure 4 metre depth cells to a water
depth of 400 meters. Recorded data was averaged over 3 minute intervals with
GPS navigation available for reference when bottom tracking was out of
range.

During the trip some problems were encountered when the Trimble GPS receiver
on the bridge failed to output the serial data feeding the ADCP.
Consequently some blocks of data recorded on June 23 and 24 will not contain
navigation data. Since we were in water depths greater than 400 meters,
bottom tracking was not possible and this data can not be reduced to actual
water velocities.

11.	Alkalinity                                            
	R. Gershey (BDR)

This cruise saw the first use of a newly developed alkalinity titration cell
based on the previous titration system. The titration cell differed in both
size and automated sample handling. It was hoped that the increase in cell
size and the automated sample handling technique would enhance both the
precision and ease of operation. New software was developed to accommodate
these changes. Preliminary results show that the expected enhanced precision
has not been realized. Thus, despite some problems with the new hardware and
software, samples from 22 of the 26 stations were taken. In all, just about
300 samples were analyzed for alkalinity.

12.	Thermometer Temperatures         
	C.K. Ross and Anthony W. Isenor (BIO)

Three electronic digital reversing thermometers (T345, T350 & T352) were
placed on bottle 1 and another three electronic digital reversing
thermometers (T347, T348 & T354) on bottle 3.

Initially, thermometer calibration data from February 1991 were used to
correct the thermometer readings. However, subsequent examination of the
corrected temperatures using post-cruise calibration data from March 1994
showed improved difference (thermometer - CTD) statistics, namely a more
peaked distribution and smaller difference from CTD.

The thermometer data were corrected using the March 1994 thermometer
calibration data. The difference (thermometer - CTD) was then computed and
the values sorted and plotted. The resulting curve showed that thermometer
T352 gave consistently large differences as compared to the CTD. This
thermometer was then removed from the analysis.

The values presented in the SEA file represent the mean thermometer
temperature, on the ITS 90 scale, computed from all thermometers excluding
T352.

The following statistics are on the differences between the readings of the
digital thermometers on the same rosette bottles:

    Thermometer Pairs            Mean Difference           Standard Deviation

        T345-T350                    -0.017                      0.007

        T345-T352                    -0.035                      0.002

        T350-T352                    -0.017                      0.006

        T347-T348                     0.003                      0.003

        T347-T354                    -0.003                      0.032

        T348-T354                    -0.006                      0.030

The following are the duplicate temperature measurements obtained from the
reversing thermometers for the indicated sample ID numbers. The temperature
values are in degrees celsius and are on the ITS90 scale. Thermometer T352
has been included in the list below although is not included in the
calculation for the CTD temperature calibration nor is it included in the
average value reported in the WOCE SEA file.

Appendix A:

93019 CTD Oxygen Calibrations

There were 26 stations occupied during cruise 93019. Based on cruise records
there were two oxygen sensors used corresponding to the following station
ranges: 1 to 19 and 20 to 26.

To create the data file to be used in the CTD oxygen calibration process,
two merges were performed. First, a temporary file was created by merging
the up trace CTD data, obtained from the CTD at the time of bottle closing,
with the down trace CTD data. The two data sets were merged using pressure.
Each record in the up CTD data file having a sample id number was combined
with the down cast 2 dbar CTD data that had the closest pressure. If no down
cast CTD data record was found, then no merged record was output for this
sample id number. The final Merged file was created by merging the temporary
file with the water sample oxygen file which contained the means of the
water sample oxygen duplicates for each sample id number.

Information from the Merged file was taken for each of the two station
ranges. Table 1 below lists the number of records for each station range
that will be used in the CTD oxygen calibration process.

Table 1.

   Station     Number of   Number of  Number of IDs not   Number of IDs having
    Range       Unique    IDs having  having a down CTD     both a mean water
               Sample ID   no water      oxygen value      sample oxygen value
                Numbers     oxygen     and/or not being   and a down CTD oxygen
                           value(s)     present in the       value that were
                                       Merged CTD file      contained in the
                                                             Merged CTD file

    1 - 19        257          4              1                    252

   20 - 26        132          2              0                    130

    TOTAL         389          6              1                    382

For reference, the mean of all the water sample oxygens collected during
this cruise was 7.016 ml/l. Using the WOCE accuracy guideline for CTD oxygen
measurements of 1-1? %, we compute a deviation of 0.07 - 0.11 ml/l. This can
be used in comparison with after calibration standard deviations.

Summary of Variables Used in Calibration Process

The following describes the notation used in the calibration.

j   : station

i   : observation taken on station j

nj : is the number of observations taken for station j

pij : pressure for the ith observation of station j

bij : water sample oxygen for the ith observation of station j

cij : down CTD oxygen for the ith observation of station j

dij = bij - cij : ith oxygen difference for station j

d.j =  : mean of the oxygen differences for station j

eij = dij - d.j : the ith oxygen difference expressed as a deviation
from the mean oxygen difference for station j

eij : predicted value of eij from the regression analysis

rij = eij - eij : ith residual for station j from the regression
analysis

kij :  calibrated CTD oxygen

since  rij = eij - eij = bij - kij

 dij - d.j - eij = bij - kij

 bij - cij - d.j - eij = bij - kij

therefore the calibration is:

Eqn 1.   kij = cij + d.j + eij

Calibration of Stations 1 to 19

Station 1 data will not be used in the calibration process because it was a
test station and all bottles were fired at the same shallow depth of 54
dbars. Using the data for stations 2 to 19 (233 data points), a plot of the
difference between the water sample oxygen and the down CTD oxygen (dij)
against pressure (pij) was produced (see Figure A-1). The data point
(outlier) having sample id number 126224 (indicated in Figure A-1) was
removed from the dataset leaving 232 points to be used in further analysis.

It was observed from Figure A-1 that a simple offset would be appropriate as
an initial calibration step. Also, the near-surface region is avoided by
omitting all data in the layer 0 to 250 dbars from the calibration process.
The 250 dbar limit was determined subjectively from Figure A-1. Omitting
data in this layer results in 150 data points to be used in the calibration.
Stations 2 to 7 had no data below the 250 dbar cut-off so they were omitted
at this point; how they were handled is discussed below.

For stations 8 to 19 the mean of the oxygen differences was calculated for
each station and this value, the station offset (d.j), was subtracted from
the individual down CTD oxygen values. The station offsets are listed in
Table 2. Figure A-2 is a plot of eij against pij. The standard deviation for
the eij's was 0.09 ml/l.

Figure A-3 is a plot of dij versus pressure for stations 2 to 7. The station
offsets were calculated for stations 2 to 7. The surface points, p <= 10
dbars, which had the large oxygen differences were removed prior to
calculating the station offsets. The station offsets and standard deviations
are given in Table 2. Figure A-4 shows eij against pressure for stations 2
to 7. The standard deviation for the eij's was 0.18 ml/l.

Calibration of Stations 20 to 26

The same steps were used for these stations as were used for stations 2 to
19, so only a brief explanation will be given. A plot of all dij against
pressure is shown in Figure A-5. All points having a pressure <= 200 dbars
were omitted leaving 103 data points for further analysis. The calculated
station offsets and standard deviations are given in Table 2. Removing the
station offsets results in Figure A-6, where eij is plotted against pij. A
linear regression analysis was performed on all the stations in the group,
using eij as the dependent variable and pij as the independent variable.
Before the regression analysis was carried out two outliers were removed,
sample id numbers 126284 and 126303; these are indicated in Figure A-6. The
regression curve is also shown in Figure A-6. There was 101 observations
used in the regression analysis.

The computed regression equation is:

Eqn. 1  eij =  0.1742 + 1.0513E04 ´ pij

A plot of the residuals (rij) versus pressure is shown in Figure A-7. The
residuals have a standard deviation 0.09 ml/l.

Station Offsets Removed in Calibration Process

The means of the oxygen differences, d.j, and standard deviations for all
stations analysed are given in Table 2 below.

Table 2. Station offsets (d.j).

Station   Mean of Oxygen Differences     Standard Deviation
                               (ml/l)

   2                        2.849                 0.59

   3                        2.212                 0.17

   4                        2.251                 0.14

   5                        2.294                 0.05

   6                        1.005                 0.19

   7                        1.123                 0.16

   8                        1.456                 0.26

   9                        1.204                 0.17

   10                       1.154                 0.04

   11                       1.140                 0.04

   12                       1.136                 0.06

   13                       1.074                 0.06

   14                       1.165                 0.12

   15                       1.145                 0.12

   16                       1.197                 0.07

   17                       1.168                 0.07

   18                       1.208                 0.08

   19                       1.187                 0.10

   20                      -1.741                 0.19

   21                      -1.655                 0.19

   22                      -1.703                 0.17

   23                      -1.667                 0.11

   24                      -1.663                 0.12

   25                      -1.647                 0.15

   26                      -1.624                 0.09

CTD Oxygen Calibration Procedure

We calibrated the CTD oxygen data for all stations according to the
following expression:

Eqn. 2  kij = cij + d.j + eij

where kij  is the calibrated CTD oxygen data

  cij is the raw CTD oxygen data,

  d.j is given in Table 2 for all stations, and

  eij  = 0 for stations 2 to 19 and eij is given by Eqn. 1 for
stations 20 to 26.

All CTD oxygen data for the listed stations, regardless of pressure, will be
calibrated using this expression.

Station 1 will be left uncalibrated since all of its bottle data was taken
at the same near surface depth.

[Image]

Figure A-1. Water sample oxygen minus CTD down cast oxygen, or dij, plotted
against pressure.

[Image]

Figure A-2. Plot of eij values against pressure for data below 250 dbars.

[Image]

Figure A-3. Water sample oxygen minus CTD down cast oxygen, or dij, plotted
against pressure.

[Image]

Figure A-4. Plot of eij values against pressure.

[Image]

Figure A-5. Plot of water sample oxygen minus CTD down cast oxygen, or dij,
against pressure.

[Image]

Figure A-6. Plot of eij values against pressure for data below 200 dbars.
The regression line is also shown.

[Image]

Figure A-7. Residuals (rij) remaining after the station and regression
offsets have been removed.
