WOCE LINE:AR18
EXPOCODE: 58JH0894_1

Cruise Report 
NORDIC WOCE 


1. 	HIGHLIGHTS

Chief Scientist:    Johan BlindheimInstitute of Marine Research, Bergen.
Co-chief Scientist: Erik BuchRoyal Danish Administration of Navigation
                    and Hydrography
Ship:               R/V JOHAN HJORT
Port of call:       Reykjavik
Cruise dates:       July 23, 1994 to August 16, 1994.


1.2. CRUISE SUMMARY.

The cruise track and station locations are shown in Fig. A.1

SAMPLING ACCOMPLISHED.

74 CTD/rosette stations were occupied using a 12 bottle rosette
equipped with 10 l Niskin bottles. Water sampling on the cruise
included measurements of CFC's (CFC-11, CFC-12, CFC-113 and carbon
tetracloride), salinity, dissolved oxygen, nitrate, nitrite, phosfate,
silicate, partial pressure of carbon dioxide, total dissolved inorganic
carbon. Additional samples were drawn and returned to shore
laboratories for analysis of tritium, helium, carbon-13 and carbon-14.

Depths were measured with a SIMRAD echosounder set with the sound
velocity set to  1500 m/sec.


1.3. LIST OF PRINCIPAL INVESTIGATORS.

Table 1.1. List of principal investigators, measurement responsibility
and institution.

Chief Scientist:    Johan Blindheim
Co-chief Scientist: Erich Buch

Principal      Measurement          Institute
Investigator   responsibility
-----------------------------------------------------
Erik Buch      CTD/Rosette          RDANH, Copenhagen
F. Rey         O2,NO3,NO2,PO4,SiO3  IMR, Bergen
E. Fogelqvist  CFCs                 Univ. Gothenburg
R. Bayer       Helium/Tritium       Univ. Heidelberg
J. Olafsson    CO2                  MRI, Reykjavik
R. Nydal       Carbon isotopes      RLD, Trondheim


1.4. PRELIMINARY RESULTS

R/V "JOHAN HJORT" departed Bergen July 23, 1994, and made 17
stations on the Norwegian Svinoy standard section on which
instruments, working and measuring procedures were tested and
optimized. On July 26 the work on the WOCE sections, shown in Fig.A.1., 
began. A change of crew took place at Reykjavik on 5 August  and the
last WOCE station was occupied on August 10. Before ending the cruise, 
four stations which are part of a Nordic Carbon Cycle Program, were
worked  north of Iceland.   

At each station CTD profiling was done with a Sea-Bird 911 Plus CTD
equipped with a 12-place SBE Carousel sampler. This CTD system
functioned satisfactorily during the whole cruise.


1.5. PROBLEMS.

On 2-3 stations single bottles did not trip.


1.6. 	LIST OF PARTICIPANTS.
     
Participant           Responcibility           Affiliation
-----------------------------------------------------------------
Johan Blindheim       Chief Scientist          IMR, Bergen
Erik Buch             Co-chief scientist, CTD  RDANH, Copenhagen
Volker Buerkel        Helium/tritium           Univ. Heidelberg
Britt-Marie Dahlberg  Salinity                 UNIV, Gothenburg
Magnus Danielsen      Carbon dioxide           MRI, Reykjavik
Elisabet Fogelqvist   CFCs                     Univ. Gothenburg
John Goddard          Carbon dioxide           LDEO, Palisades, NY
Merete Fonn           Nutrients/oxygen         IMR, Bergen
Magnar Mjanger        Instrument tech.         IMR, Bergen
Jon Mortensen         CTD                      Univ. Copenhagen
Kjell Arne Mork       CTD                      Univ. Bergen
Reidar Nydal          C-13, C-14               Univ. Trondheim
Jon Olafsson          Carbon dioxide           MRI, Reykjavik
Marek Ostrowski       Data processing          IMR, Bergen
Francisco Rey         Nutrients/oxygen         IMR, Bergen
Jane Stromstad        Nutrients/oxygen         IMR, Bergen
Toste Tanhua          CFCs                     Univ. Gothenburg
Hedinn Waldimarsson   Data processing          Mri, Reykjavik
Christoph Wagner      CTD                      RDANH, Copenhagen


2.   DESCRIPTION OF MEASUREMENT TECHNIQUES AND CALIBRATION.

2.1. CTD MEASUREMENTS.
     (Erik Buch)

The CTD measurements were carried out using a SeaBird 911 Plus CTD
equipped with dual temperature and conductivity sensors. The CTD was
mounted together with a  12-place SeaBird Carousel Sampler and 10 l
Niskin bottles.

The temperature and conductivity sensors were calibrated at the
SeaBird calibration facility before and after the cruise. In addition,
conductivity was calibrated at sea using data from the analyses of the
salinity samples.

The CTD pressure sensor is Paroscientific Digiquarts model 410K-015
having a resolution of  0.001% of full scale i.e. 0.07dbar and a accuracy
of 0.015% of full scale i.e. 1 dbar.

The temperature sensors used were SeaBird SBE 3 having a resolution
of 0.0002°C and an accuracy of 0.002°C. Pre- and post cruise
calibrations (23 Apr 94 and 01 Sep 94) at SeaBird calibration facility
showed a drift of  0.0022 °C/year for the primary thermometer and
0.0011°C/year for the secondary. Both thermometers  were accurate
within 0.0001°C in both calibrations.

The conductivity sensors used were Seabird SBE 4 having a resolution
of 0.00004 S/m and an accuracy of 0.0003 S/m. Pre- and post cruise
calibrations at the Seabird calibration facility (23 Apr 94 and 01 Sep
94) showed a drift of 0.00005 S/m/month for the primary  sensor and
0.000025 S/m/month for the secondary sensor, both at a conductivity
of 3.0 S/m.  

The CTD data were collected and processed using the Seasoft version
4.032 software provided by Seabird, installed on a TCI personal
computer (486, 66mHz).


2.2. SALINITY MEASUREMENTS.
     (Johan Blindheim)

Water samples for salinity analysis were collected from almost all 
sampling depths, normally 12 or 24 samples on every station. After
temperature stabilization, the samples were analysed on board using a
Guildline 8400 Autosal  salinometer  within a day or two after
collection. Salinometer readings were controlled against  IAPSO
Standard Sea Water, Batch  P124, after each  24th sample bottle.

The salinometer was placed in a temperature stabilized laboratory
where the temperature was kept  between 22°C and 24 °C throughout
the cruise. Each sample was determined at least 3 times and the
standard deviation between the multiple determinations throughout the
cruise was 0.00048 (double conductivity ratio). The standard deviation
between 45 multiple samples during the cruise, drawn from the same
Niskin bottle, was 0.0009 in salinity.

Data from the salinity samples at pressures of 1000 dBar or greater
were used for in situ calibration of the CTD. The relation  between
primary CTD conductivities and conductivity of the samples at the
same pressure and temperature is given by:

                       DELC = -1.5194 E-2 + 4.6145 E-4 * C

Here C is the CTD conductivity reading and DELC is the correction which
has to be added to the  CTD conductivity reading. We are of the opinion
that this gives a more correct calibration than a fit with a slope and no
offset which is recommended by the manufacturer.


2.3. OXYGEN MEASUREMENTS.
     (Francisco Rey)

Oxygen concentrations were measured with the Winkler method with
visual determination of the titration endpoint. Samples were collected
into 120 ml volume calibrated bottles, added pickling reagents, shacked
and left for about two hours after which it were shacken again. After
adding acid the whole sample was carefully poured into a 200 ml
Erlenmeyer flask and titrated using a 20 ml automatic burette (
Schott-Gerätte T90/20) with a dispensing precision of 0.01 ml.

All reagents were prepared with p.a. quality chemicals closely
following WOCE recommendations ( Culberson, 1991). Standarization of 
the 0.01N thiosulphate solution was done with potassium biiodate
(0.0100 N).

The precision of the method was determined several times for each of 
the two analysts during the cruise by analysing 10 replicates collected
from a single 10 liter Niskin bottle. The lowest precision obtained by
the less trained analyst was of 0.23 % ( standard deviation 0.55 µmol
kg-1 at a concentration of about 237 µmol kg-1). The lowest precision
for the other analyst was 0.13 % ( 0.39 µmol kg-1 at a concentration of
301 µmol kg-1).

Oxygen concentrations were calculated in ml l-1 and converted to
weight concentrations by using  the equation recommended by WOCE
(Culberson, 1991). The density of the seawater was also calculated by
the equation recommended by Culberson (1991) using salinity and
potential temperature values recorded by the Seabird CTD probe at the
depth where the Niskin bottles were triggered.

REFERENCES.

Culberson, C.H.(1991). Dissolved oxygen. WOCE Operations Manual.
    Vol.3, Section 3.1, Part 3.1.3: WHP Operations and methods. WHP Office
Report WHPO 91-1, WOCE Report No. 68/91, Woods Hole,Mass,.USA.


2.4. NUTRIENT MEASUREMENTS
     (Francisco Rey and Jane Stromstad)

Seawater samples were collected into polyethylene test tubes with
pressure caps and kept refrigerated at 4°C in the dark. Analysis of
nitrate, nitrite, phosphate ans silicate were carried out within 12
hours after collection with an autoanalyzer that comprised the
following units:

€ Pumping system from ChemLab, England.
€ Reaction units of own fabrication
€ Autosampling, detection and computing units from SANplus Segmented Flow 
  Analyzer, Skalar Analytic B.V., the Netherlands.

The methods used were adaptations of standard methods (Strickland
and Parsons, 1981) slightly modified to the autoanalyzer system ( Foyn
et al.,1981). A new modification was applied during the cruise for  the
analysis of nitrate. The Cd-reduction column used this time was a Cd-
tube manufactured by Alpkem Inc. and the segmentation of the flow was
achieved by pumping nitrogen gas instead of air as in the previous
version of the method.

The precision of the analyses was monitored by running ten replicates
samples from a single Niskin bottle several times during the cruise.
The precision obtained for the different analyses at full scale was
better than 0.1% for nitrite, 0.25% for nitrate, 1.5% for phosphate and
0.2% for silicate. The precision of the phosphate analysis it seems to
have been affected by the use of new polyethyelene tubes at the start
of the cruise. After soaking the tubes in seawater and rinsing them
with distilled water before use the precision improved to about 1% at
full scale.

The reproducibility of the analysis was assesed by running a set of
control samples which were newly made every day from stock solutions
prepared ashore. The control samples were prepared in low nutrient
seawater and were run in the same way as the other samples. The
obtained reproducibility ( one standard deviation) during 14  days for
the different analysis were:

  € Nitrite     : 0.39 % at a level of about  0.50 µmol l-1 

  € Nitrate     : 1.14 % at a level of about  8.10 µmol l-1  
                : 0.50 % at a level of about 18.00 µmol l-1  

  € Phosphate   : 1.16 % at a level of about  0.66 µmol l-1  
                : 0.52 % at a level of about 1.250 µmol l-1  

  € Silicate    : 0.36 % at a level of about  4.50 µmol l-1  
                : 0.10 % at a level of about 11.00 µmol l-1  

REFERENCES:

Foyn, L., M. Magnussen and K. Seglem (1981). Automatic analysis of nutrients 
          with an online dataprocessing. A presentation of construction and 
          functioning of the system used at the Institute of Marine Research. 
          Fisken Hav., Serie B, 1981(4): 1-9. In Norwegian.
Strickland, J.D.H. and T.R. Parsons(1972). A practical handbook of seawater 
          analysis, 2nd. ed. Bull.Fish.Res.Bd.Can. No.167.


2.5. MEASUREMENTS OF TOTAL DISSOLVED CO2, DELC14 AN DELC13.
     (Reidar Nydal)

SAMPLING STRATEGY AND PROCEDURE.

The main goal for the cruise was to get some basic carbon profiles
north and south of the Denmark Strait Ridge, as a contribution to the
study of water overflow. It was especially important to repeat one
GEOSECS profile from 1972. Fairly complete carbon profiles were
performed at 4 stations.The changes in the profiles during a period of
20 years could give valuable information about the water exchange
with depth.

The samples were collected in 500 ml glass bottles, which first were
rinsed with some of the sampling water, and then filled up.. The
samples were stored in a refrigerator and analysed within a few days.

EQUIPMENT AND TECHNIQUE.

The extraction of total dissolved CO2 from 500 ml seawater was
carried out onboard shortly after collection. A bubbling procedure with
nitrogen (99.99%) as a carrier gas, in a closed cycle, was applied for
this purpose. The sample was acidified in advance with phosphoric acid
to a pH value of 1.5. The bubbling lasted for 15 minutes. The water was
removed from the CO2-gas using vapor traps (-80oC) and a drying agent
(P2O5). CO2 was continously trapped with liquid nitrogen (-196oC)
during the cycle. After the flushing was finished nitrogen was removed
and the CO2-gas was trapped in 25 ml glas ampulles for later
measurements in the laboratory after return.

The quantitative measurements of the CO2-gas are performed with an
oil manometer. The obtained precision (standard error) in a single
measurement, derived from several measurements of identical
samples, has been found to be less than 3 permill. The present
procedure for CO2-extraction is develloped at the Radiological Dating
Laboratory.

The obtained CO2-gas (ca 25 ml.) is applied for both 13C/12C (ca.5 ml)
and 14C/12C AMS measurements (ca 2 ml). The measurements of
DELC13 will be carried out in a mass spectrometer at the geological
Institute, Univ. of Bergen. The precision in each measurement is about
0.1 permill. 14C measurements will be performed with the AMS
(accelerator mass spectrometry) facility in Tucson, Univ. of Arizona
with a precision of about 4 permill.


2.6. TOTAL DISSOLVED INORGANIC CARBON (TCO2), PARTIAL PRESSURE OF CO2
     IN SEAWATER (pCO2).
     (Jon Olafsson and John Goddard)

TOTAL DISSOLVED INORGANIC CARBON.

Total CO2 measurements are made ashore on discrete seawater
samples collected at various depths. An approximately 20 ml subsample
is injected by positive displacement syringe into a stripping column.
Acidification converts all inorganic carbonate species in the sample
into CO2 gas which is then swept into a electrochemical titration cell.
The titration results are measured using a Utopia Instruments Corp.
(UIC) model 5011 Coulometer. The performance of the instrument is
monitored several times daily using a gas loop calibration system.
Overall analytical quality control is evaluated daily with reference
material for oceanic CO2 measurements. This reference material is
kindly supplied by Dr. A. Dickson of Scripps Institution of Oceanography,
USA. After final processing, results are reported as TCO2 10-6 moles
/kg.

PARTIAL PRESSURE OF CO2 IN SEAWATER (pCO2).

The pCO2 analysis system uses a closed system seawater equilibrator
to bring the partial pressure of CO2 of discrete seawater samples into
equilibrium with a small quantity of air, and a gas chromatograph to
analyze the concentration of CO2 in the equilibrated air. The gas
chromatograph uses a flame ionization detector (FID), which is
insensitive to CO2, but which has a highly liniar response to
hydrocarbons. Using hydrogen as a carrier gas and a ruthenium catalyst,
the CO2 is converted completely to methane prior to reaching the FID.
The highly sensitive and liniar FID is thus used to quantify the CO2
content of the equalibrated air. The discrete seawater samples are
collected in 500 ml flasks and are equilibrated a constant temperature
bath at 4oC. After corrections and final processing, results are
reported as pCO2 10-6 atm at 20oC.


2.7. CHLOROFLUOROCARBON TRACER MEASUREMENTS.
     (Elisabet Fogelqvist)

The chlorofluorocarbons provide a powerful tool for studying time
scales and magnitudes of large-scale oceanic subsurface mixing and
deep water renewal processes. Four chlorofluorocarbon tracer
compounds, namely CFC-11, CFC-12, CFC-113 and carbon tetrachloride
(also classified as CFC-10), were measured. Carbon tetrachloride has
been present in the atmosphere since the beginning of this century, the
two CFCs 11 and 12 since the forties and CFC-113 since the beginning
of the seventies, all at increasing concentration levels. Equilibration
with seawater at the sea surface gives a time dependent signature of
the surface waters that can be traced.

Seawater samples were analysed for the CFCs at 70 stations, i.e. all
but four of the stations and at most of the depths sampled for chemical
measurements. Water samples, drawn directly from the sampling
bottles into 100 ml ground glass syringes, were analysed using a
purge-and-trap sample work-up technique followed by gas
chromatographic separation on a 75 metres long megabore open tubular
column and electron capture detection. The entire analytical set-up
was built with two identical channels, whereby two water samples
were analysed simultaneously utilising a gas chromatograph holding
two separation columns and two detectors. The standardisation was
made with a standard gas mixture, which was calibrated against a
standard supplied by Dr. Andrew Watson, Plymouth Marine Laboratory,
England. The two detectors of the analytical set-up, standardised
separately, showed standard curves that were best fit to a polynomial
function of the second order.

The reproducibility of the analytical method was measured from
replicate samples of a deep water (800 m) with moderate CFC
concentration levels. The relative standard deviations (RSD) in the first
channel of the analytical system were 0.8%, 1.0%, 6.0%, and 1.1% for
CFC-11, CFC-12, CFC-113 and CFC-10, respectively. In the second
channel, the corresponding RSDs were 1.0%, 1.5%, 2.4% and 1.1%. The
detection limits of CFC-11, CFC-12 and CFC-10 are estimated to 0.01
pmol/kg and somewhat higher, 0.02 pmol/kg, for CFC-113.


2.8. HELIUM/TRITIUM SAMPLING.
     (Volker Buerckel)

GENERAL ASPECTS.

Tritium is the radioactive isotope of hydrogen. It decays with an
halflife of 12.43 years to the helium isotope He-3. The major source
for tritium was the nuclear weapon testing in the atmosphere mainly in
the 1960s.

At the seasurface He-3 concentrations usally are close to solubility
equilibrium with the atmosphere. Water isolated from the surface due
to convection will be enriched in tritiogenic He-3 while spreading
along the isopycnals. The tritiogenic He-3 is detectable as a deviation
of the He-3/He-4 ratio of the water sample from that of an air
standard. Measurements of both He-3 excess and tritium concentration
allow calculation of a formal tritium/He-3 age, which is a tool for
estimation of mean transfer times, current speeds and renewal times.

SAMPLING.

During the cruise 143 samples for measurement of both helium and
tritium were taken. The helium samples (volume about 40 cc) were
stored in copper tubes closed tightly at both ends by means of special
stainless steel pinch-off clamps.

For tritium analysis 250cc of water was stored in a glass bottle sealed
by a polyethylen cap.

MEASUREMENT.

The analyses will be performed at Univ. of Heidelberg. For
measurements of He-3/He-4 ratio a special helium isotope mass
spectrometer with an accuracy of about + 0.2% is used. Tritium
measurements in Heidelberg are either done by low level counting (with
an accuracy of +5%) or by mass spectrometry (He-3 ingrowth method
with an accuracy of about +2% and a detection limit of 0.05 TU). Data
will be available during 1995.
 

