preliminary data report
may 4,1995


A. Cruise Narrative

A.1.	Highlights

A.1.a	WOCE designation:		AR7W
A.1.b	EXPOCODE:			18DA90012_1

A.1.c	Chief Scientists:		John Lazier
					Bedford Institute of Oceanography
					P.O. Box 1006
					Dartmouth, N.S.
					Canada B2Y 4A2 
					Phone: 902-426-2558
					Telefax: 902-426-7827
					Internet: J_lazier@bionet.bio.dfo.ca

A.1.d	Ship:				CSS Dawson

A.1.e	Ports of Call:	

A.1.f	Cruise Dates:		July 2 - 9, 1990

A.2	Cruise Summary


A.2.a	Geographic Boundaries




A.2.b	Total number of stations occupied

A.2.c	Floats and drifters deployed

A.2.d	Moorings deployed or recovered


A.3 	List of Principal Investigators

Table 2: List of Institutions

Abbreviation	Institution

BIO			Bedford Institute of Oceanography
			P.O. Box 1006
			Dartmouth, N.S.
			Canada B2Y 4A2 

BDR			BDR Research
			P.O. Box 652, Station M
			Halifax, N.S.
			Canada B3J 2T3


A.4	Scientific Programme and Methods
 	
The purpose of this cruise was to occupy the WOCE AR7/W repeat section across 
the Labrador Sea.  This section has been selected for repeat obsevations because 
it is at or near the sources of three of the major water masses of the North 
Atlantic Ocean; the Labrador Sea Intermediate Water, the North Atlantic Deep 
Water and the Denmark Strait Overflow Water.  All these water masses contain 
significant fractions of Arctic water which enters the North Atlantic 
principally over the sills in Davis Strait and between Greenland and 
Scotland.The characteristics and/or quantities of these overflowing waters vary 
over time because of changing meteorological and oceanographic conditions and 
these variations are reflected in the properties of the northern water masses.  

Some significant variations have already been observed.  For example, from 1967 
to 1971 the summer-time salinity of the near surface water in the central 
Labrador Sea decreased by ~ 0.6 (~3 times the annual range) because of an 
unusually large flow of fresh water out of the arctic.  Over the intervening 
years this lower salinity water has mixed down to ~2000 m via deep convection 
and lowered the salinity of the Labrador Sea Intermediate Water by ~0.07.  As 
the density of the water remains roughly constant the drop in salinity has been 
accompanied by a drop in temperature of ~0.40C.  The temperature and salinity of 
the Denmark Strait Overflow Water have also been observed to change 
significantly over the past 25 years.  

By observing the properties of the three main water masses in the Labrador Sea 
once a year throughout the five year WOCE observing period we hope first to 
specify anomalous properties before they are advected into the main body of the 
Atlantic Ocean and second to identify, where possible, correlations between 
anomalous properties and changes in the meteorological/oceanographic conditions. 

The first 9 stations constitute a short line up the middle of the Labrador Sea 
to help us position the WOCE AR7/W line (stations 10 to 31) and to get the 
instru-ments and staff in top working condition.  One of the main criteria for 
the position of the line was that it pass through the slow cyclonic gyre which 
dominates the circulation in the central Labrador Sea.  This gyre contains 
thesource waters of the Labrador Sea Intermediate Water.  The line was also 
placed to pass across Hamilton Bank on the southern Labrador shelf were a 
mooring programme has been conducted for a number of years.

There was a decrease in the later deep stations in the number of oxygen 
samplesdue to an unfortunate lack of the required chemicals.  

Over the Greenland and Labrador shelves, sub-zero water of ~33 salinity flows in 
the West Greenland and Labrador Currents.  Over the Greenland slope, indicated 
by the 40C isotherm and 34.90 salinity contours at 200-400 m, is a warm-saline 
remnant of the Irminger Current which becomes part of the East Greenland Current 
before it rounds Cape Farewell to become the West Greenland Current.  In the 
central part of the section from roughly 200 m to 2000 m lies the Labrador Sea 
Intermediate Water obviously very homogeneous in its properties staying for the 
most part between 3.0 and 3.20 C and between 34.82 and 34.84 salinity.  Below 
2000 m to about 3200 m is the North Atlantic Deep Water identified by a salinity 
maximum and below, next to the bottom at a salinity of <34.90 is the Denmark 
Strait Overflow Water.     

Preliminary comparisons with reversing thermometers indicate the CTD measured 
temperatures to within +/-0.005.  Comparisons with salinity samples suggest the 
CTD values are low by ~0.005 from 0-2000m.  Between 2000 and 4000 m there is a 
linear decrease such that the CTD measures low by 0.012 at 4000 m.  

Computer Report  (by Paul Dunphy)   The MicroVAX II system performed well on 
this cruise.  Loran C navigation data was logged non-stop throughout the cruise.  
There was one 20 minute period where we experienced several power failures and a 
small portion of this navigation data was lost.  These data are not essential to 
the program and no attempt was made to retrieve it.  In the past we have had no 
success recoveringsuch data in files left open due to power loss.     

Thirty-one CTD stations were logged successfully.  We used the 1990 version of 
the PIPE processing software to do both real time and post acquisition analysis.  
Minor modifications were made to the directive files to tailor them to the 
scientific program.  In addition to the usual PIPES (real time, plottingand 
processing), two other plotting PIPES were added for each down cast.  This made 
a total of two logging processes and six analysis PIPES running at once.  During 
this time other tasks such as editing and backing up data files were extremely 
slow.  We attributed the degradation in speed to the smaller memory size on the 
DAWSON system (7 Mb).     

Between stations we processed and plotted the CTD data a number of times using 
various primitive combinations.  No errors were found.     

The only serious concern was the performance of the TK-50 tape drive.  Soon into 
the cruise it began reporting that it was losing the position of the tape.After 
several days of sporadic problems, it failed completely and would not mount or 
initialize tapes.  Re-booting did not clear the problem.  I 
consideredreinstalling the operating system but it was on a TK-50 tape.  I could 
not tell if it was a software or hardware problem.     

Account and data backups were made on using the EXABYTE tape system.  Both the 
EXABYTE and external disk performed flawlessly.     

In summary, the computer presented few problems during the cruise.Both watch 
keepers had substantial experience both with the system and the CTD operation 
and this was a major factor in previous years, thanks to John O'Neillof the 
software shop for putting in the extra effort prior to our sailing.   

A.5	Major Problems and Goals Not Achieved

A.6	Other Incidents of Note

A.7	List of Cruise Participants


Table 3: list of Cruise Participants

Name	Responsibility  	Institution*
		
John Lazier	Sr. Scientist	BIO
Rick Boyce	Oxygens	BIO
Bruce Carson	CTD/Rosette	BIO
Paul Dunphy	Computer/Data	BIO
Bob Gershey	CFC & CCl4	BDR Research
Jennifer Hackett	Computer/Data	BIO
Mike Hingston	CFC	BDR Research
Marion Smith	Computer/Data	BIO
Frank Zemlyak	CFC & CO2	BIO

*See Table 2 for list of Institutions

B. 	Underway Measurements

B.1	Navigation and bathymetry
B.2	Acoustic Doppler Current Profiler (ADCP)
B.3	Thermosalinograph and underway dissolved oxygen, flurometer, etc
B.4	XBT and XCTD
B.5	Meteorological observations
B.6	Atmospheric chemistry
C.	Hydrographic Measurements

C.1	Measurements of Halocarbons and Total Inorganic Carbon
(by F.  Zemlyak, R.M.  Gershey and M.P.  Hingston) 

Objectives 

(1)	To test new instrumentation for the measurement of various halocarbons in 
sea water by a purge-and-trap gas chromatographic method.

(2)	To test a coulometric titratorfor the measurement of total inorganic 
carbon in sea water. 

(3)	To make measurements of the above chemical species in water samples 
collected from the Labrador Sea.

Background   

The instrumentation mentioned above has been developed at the marine chemistry 
division of the Bedford Institute of Oceanography under a PERD funded program 
managed by P.Jones.  The main objective of this program is to develop approaches 
to model the rate of transport of carbon dioxide gas from the atmosphere to the 
deep ocean.  The flux of atmospheric CO2 to the ocean can be estimated from 
measurements of alkalinity, total CO2, various transient tracers and a knowledge 
of the large scale convective transport of surface water to the deep ocean.     

The first phase of this project has largely been concerned with the design and 
construction of instruments to measure these tracers and total inorganic carbon 
in sea water.  The halocarbon system is a modification of a system used 
previously at BIO.  The most important improvement in the new design is the 
capability to measure a larger suite of compounds including the 
chlorofluorocarb-ons (CFC-12, CFC-11, CFC-113), 1,1,1-trichloroethane and 
carbon-tetrachloride.  In addition to these man-made compounds, the system may 
also be able to measure other volatile halocarbons that are produced by 
organisms in seawater, such as bromoform, methyl bromide, methyl iodide and 
other halogenated species.     

The method used for the determination of total carbonate involves acidification 
of the sample with phosphoric acid, purging the evolved CO2 from the sample with 
a stream of nitrogen and detection of the same with a coulometricdetector.  For 
the purposes of modelling the rate of CO2 transport, total inorganic carbon must 
be measured with a precision of 1-2 parts per thousand. An automated system was 
tested on previous cruises and found to produce data with inadequate precision.  
This instrument was modified and brought on the present cruise for further 
testing.  


Work Done

Halocarbons: This cruise provided the first opportunity to test this 
newlydeveloped method at sea.  Several days were required to make the instrument 
operational and to purge the system of contamination.  One of two 
chromatographic columns could not be adequately cleaned and was removed from the 
system.  As a result, the ability to separate and measure CFC-12 was lost. 
However, the system as operated during the cruise was able to determine the 
concentrations of CFC-11, CFC-113, and carbon tetrachloride (CCl4). Water 
samples were taken from seventeen stations and depth profiles of the three 
compounds mentioned above were produced. In addition to these identified 
peaks,chromatograms of the sea water samples showed eight additional well-
resolved peaks.  Work will be done in the laboratory to identify these 
compounds.  Likely candidates are 1,1,1-trichloroethane, and the bromine and 
iodine-containing compounds that are produced by algae.  

Total inorganic carbon: At each station, water samples were taken for total 
inorganic carbon analysis from the same bottles as were the halocarbon 
samples.The instrument did not, however, produce results that were of 
consistently high quality.  Two aspects of the system were found to be the major 
contributors to this problem.  A leaking rotary valve contaminated samples with 
extraneous carbon dioxide and prevented accurate standardization.  Secondly, the 
performance of the coulometer's titration cell appeared to degrade prematurely 
during use, apparently the result of interfering compounds entering through the 
gas stream. 

Summary  		A new halocarbon measurement system was successfully setup and 
operated during the cruise.  Profiles of CFC-11, CFC-113 and CCl4 were obtained.  
These are the first measurements of CCl4 profiles at sea by a purge-and-trap 
method. Testing of the automated system for the determination of total inorganic 
carbon revealed that data with adequate precision could be attained, but that 
this was not realized on a routine basis.  Several problems with the instrument 
were identified as a result of our tests.   

C.2	Oxygen Titrations    (by Rick Boyce) 		The titration system was 
set up to attempt to standardize the thiosulphate solution (titrant).  It was 
quickly discovered that the Metrohm 655 Dosimat was inoperative in the mode used 
with the PC computer.  It was replaced with a spare and all was fine, for the 
time being.  The thiosulphate solution was standardized and blanks run using 
both distilled water and seawater giving the following results: 

Standard Titration Volumes	Blank Titration Volumes 
1.767	0.008
1.766	0.013
1.769	0.012
1.761	0.010



All looked in readiness and the samples 73201 - 73220 from CTD #1 were sigma-t 
vs dissolved oxygen curve quite well.  

During the next few days samples 73221 - 73340 from stations 2-6 were offset 
with respect to the historic curve.  When the thiosulphate and blanks were 
rechecked, it was discovered that the standard had changed from an average of 
1.766 to 1.880 (weaker).  The blanks were OK.  Recalculating the oxygens with 
this new value appeared to remove the offset for stations 2 - 6 but imposed an 
offset for station 1, which would be expected since station 1 looked OK with the 
original value for the standardization of the thiosulphate.  	

For samples 73341 - 73343, the PC 800 Colorimeter could not be adjusted 
Colorimeter had a LED segment missing which made it difficult to distinguish 
between the numbers 8 and 9.  

For the first few stations the duplicates were quite good but afterwards they 
tended to get worse.  At sample 73382, it was noticed that the piston assembly 
in the Dosimat had been leaking.  It was changed and the system once again 
appeared to work properly, as did the duplicates.  

At sample 73452, the remaining thiosulphate solution was saved and sealed in the 
original container.  The second half of the solution was used for the remaining 
titrations.  At this point, the standard iodate solution had been depleted 
making standardization of the second aliquote of thiosulphate impossible.  At 
sample 73512, the thiosulphate solution was running low which resulted in the 
cutting back on the number of oxygen samples per cast.  The oxygen samples for 
the last two stations were not run because of lack of titrant. What was left was 
sealed and stored to be restandardized back at BIO.

D.	Acknowledgements

E.	References

Unesco, 1983. International Oceanographic tables. Unesco Technical Papers in 
Marine Science, No. 44.

Unesco, 1991. Processing of Oceanographic Station Data, 1991. By JPOTSeditorial 
panel.

F.	WHPO Summary

Several data files are associated with this report.  They are the da9012.sum, 
da9012.hyd, da9012.csl and *.wct files.  The da9012.sum file contains a summary 
ofthe location, time, type of parameters sampled, and other pertientinformation 
regarding each hydrographic station.  The da9012.hyd file contains thebottle 
data. The *.wct files are the ctd data for each station.  The *.wct files are 
zipped into one file called da9012wct.zip. The da9012.csl file is a listingof 
ctd and calculated values at standard levels.

The following is a description of how the standard levels andcalculated values 
were derived for the da9012.csl file:

Salinity, Temperature and Pressure:  These three values were smoothedfrom the 
individual CTD files over the N uniformly increasingpressure levels using the 
following binomial filter-

t(j) = 0.25ti(j-1) + 0.5ti(j) + 0.25ti(j+1) j=2....N-1

When a pressure level is represented in the *.csl file that is notcontained 
within the ctd values, the value was linearly interpolatedto the desired level 
after applying the binomial filtering.   

Sigma-theta(SIG-TH:KG/M3), Sigma-2 (SIG-2: KG/M3), and Sigma-4(SIG-4:KG/M3): 
These values are calculated using the practical salinity scale(PSS-78) and the 
international equation of state for seawater (EOS-80)as described in the Unesco 
publication 44 at reference pressures of thesurface for SIG-TH; 2000 dbars for 
Sigma-2; and 4000 dbars for Sigma-4.

Gradient Potential Temperature (GRD-PT: C/DB 10-3) is calculated as theleast 
squares slope between two levels, where the standard level is thecenter of the 
interval.  The interval being the smallest of the twodifferences between the 
standard level and the two closest values.The slope is first determined using 
CTD temperature and then theadiabatic lapse rate is subtracted to obtain the 
gradient potentialtemperature.  Equations and Fortran routines are described in 
Unescopublication 44.

Gradient Salinity (GRD-S: 1/DB 10-3) is calculated as the least squaresslope 
between two levels, where the standard level is the center of thestandard level 
and the two closes values.  Equations and Fortranroutines are described in 
Unesco publication 44.

Potential Vorticity (POT-V: 1/ms 10-11) is calculated as the verticalcomponent 
ignoring contributions due to relative vorticity, i.e.pv=fN2/g, where f is the 
coriolius parameter, N is the bouyancyfrequency (data expressed as radius/sec), 
and g is the localacceleration of gravity. 

Bouyancy Frequency (B-V: cph) is calculated using the adiabaticleveling method, 
Fofonoff (1985) and Millard, Owens and Fofonoff(1990).  Equations and Fortran 
routines are described in Unescopublication 44.

Potential Energy (PE: J/M2: 10-5) and Dynamic Height (DYN-HT: M) arecalculated 
by integrating from 0 to the level of interest.  Equations and Fortran routines 
are described in Unesco publication, Processing of Oceanographic station data.

Neutral Density (GAMMA-N: KG/M3) is calculated with the program GAMMA-N(Jackett 
and McDougall) version 1.3 Nov. 94.  

G.	Data Quality Evaulations

DQE of CTD data for the 90012/1 1990 cruise of the r/v "Dawson", WOCE section 
A7W in the Northern Atlantic. Eugene Morozov Data quality of 2-db CTD 
temperature and salinity profiles and reference rosette samples were examined.  
Vertical distributionsand theta-salinity curves were compared for individual 
stations using the data of up and down CTD casts and rosette probes.  Data of 
several neighboring stations were compared.  The data were compared with the 
92/14  and 93/19 cruises of the r/v "Hudson" carried out in the same region.    
Questionable data in *.hy2 file were marked in QUALT2 word.   The CTD oxygen 
data were flagged not calibrated  by originators. The latest information is that 
analysys is not yet received for all bottle oxygen data. The flag should be - 1.  
The differences between CTDOXY data and OXYGEN were so great that data need a 
more thorough analysis by the originators.  Only minor remarks were made 
concerning the bottle OXYGEN data.  CTDOXY data are unreasonably high and should 
be calibrated.

Listing of results from the comparison of salinity data.  Only thosestations and 
pressures are listed which have data remarks.

Stat.	Press.	Remarks
 		
1	390 db	SALNTY is high 34.822 compared with upcast CTDSAL 34.815 
			and downcast CTDSAL 34.814
			flag 4
                                                                		
	1960 db	SALNTY is  low 34.865 compared with upcast CTDSAL 34.874 
			and downcast CTDSAL 34.883 
			flag 4  
                                                                		
	3728 db	SALNTY is  low 34.887 compared with upcast CTDSAL 34.889 
			and downcast CTDSAL 34.890, (this is the deepest level and 
			there was no time lag between the bottle measurement and 
			downcast CTD
			flag 3.
		
2	1991 db	SALNTY is low 34.902 compared with upcast CTDSAL 34.912 
			and downcast CTDSAL 34.910 
			flag 4  
                                                                		
	3397 db	SALNTY is high 34.910 compared with upcast CTDSAL 34.904 
			and downcast CTDSAL 34.907
			flag 3.
		
3	585 db 	SALNTY is high 34.828 compared with upcast CTDSAL 34.819 
			and downcast CTDSAL 34.821 
			flag 4  

3	2494 db	SALNTY is  low 34.916 compared with upcast CTDSAL 34.926 
			and downcast CTDSAL 34.926
			flag 4.
		
4	980 db	SALNTY is high 34.837 compared with upcast CTDSAL 34.830 
			and downcast CTDSAL 34.830 
			flag 4  
                                                                		
	1240 db	SALNTY is high 34.834 compared with upcast CTDSAL 34.831 
			and downcast CTDSAL 34.828
			flag 3.
		
11	201 db	SALNTY is low 34.391 compared with upcast CTDSAL 34.409. 
			Downcast CTDSAL 34.192, is much lower which is probably 
			associated with a high horizontal salinity gradient in coastal 
			Greenland waters, 
			flag 3 for SALNTY  
                                                                		
	260 db	SALNTY is VERY high 34.898 compared with upcast CTDSAL 34.700 
			and downcast CTDSAL 34.648 no other idea but to flag both 
			SALNTY and upcast CTDSAL bad 
			flag 4.
		
13	3160 db	SALNTY is slightly low 34.881 compared with upcast CTDSAL 
			34.884 and downcast CTDSAL 34.885
			flag 3.
		
14	3047 db	SALNTY is high 34.915 compared with upcast CTDSAL 34.903 
			and downcast CTDSAL 34.904
			flag 4.
		
16	2777 db	SALNTY is high 34.939 compared with upcast CTDSAL 34.918 
			and downcast CTDSAL 34.922
			flag 4.
		
20	3564 db	SALNTY is  low 34.879 compared with upcast CTDSAL 34.883 
			and downcast CTDSAL 34.884
			flag 3.
		
21	995 db	SALNTY is high 34.839 compared with upcast CTDSAL 34.827 
			and downcast CTDSAL 34.829
			flag 4.

	3545 db	SALNTY is low 34.878 compared with upcast CTDSAL 34.881 
			and downcast CTDSAL 34.881 (this is the deepest level and 
			there was no time lag between the bottle measurement and 
			downcast CTD,
			flag 3.
		
	24757 db	SALNTY is high 34.853 compared with upcast CTDSAL 34.834 
			and downcast CTDSAL 34.835
			flag 4.



OXYGEN measurements from station 15, 1411 db and station 16, 506 dbseem very low 
compared with neighboring levels and stations.  Thereare no minimums on upcast 
and downcast CTDOXY measurements (though they are not calibrated).  I consider 
these data Qble althoughthe whole data set is not ready yet.
