A.   CRUISE NARRATIVE:  AR13 AND AR27



A.1. HIGHLIGHTS

                       WHP CRUISE SUMMARY INFORMATION

                   WOCE section designation  AR13 and AR27
          Expedition designation (EXPOCODE)  06AZ172
                Chief Scientist/affiliation  Monika Rhein/IfMK*
                                      Dates  1998.Jul.14 - 1998.Jul.30
                                       Ship  RV Valdivia
                              Ports of call  unknown
                         Number of stations  47
                                                        59°N 
      Geographic boundaries of the stations  58°W                42°W
                                                        46°N
               Floats and drifters deployed  unknown
             Moorings deployed or recovered  unknown
                       Contributing Authors  M. Rhein

              *Institut für Meereskunde ~ 24105 Kiel ~ Germany
       now at Institut für Ostseeforschung ~ 18119 Rostock ~ Germany
       email: monika.rhein@io-warnemuende.de ~ mrhein@ifm.uni-kiel.de

             CFC-Lab: Martina Elbrächter and Kristin Bahrenfuss
              Institut für Meereskunde ~ 24105 Kiel ~ Germany
                     email:melbraechter@ifm.uni-kiel.de



SUBPOLAR NORTH ATLANTIC CHLOROFLUOROCARBONS: LABRADOR SEA
(Monika Rhein)
12/21/2000


SAMPLE COLLECTION AND TECHNIQUE

The water samples were drawn from precleaned 10 L Niskin bottles with gas tight 
100 mL glass syringes (Becton and Dickinson). CFCs were measured on board with 
a GC-ECD (Electron Capture Detector) technique first described by Bullister and 
Weiss [1988]. About 15-25 mL were transferred to a purge and trap unit. The 
CFCs were separated on a packed stainless steel column filled with Porasil C 
and detected with an ECD. The carrier gas is ECD pure Nitrogen, which was 
additionally cleaned by molsieves (13X mesh 80/100).

All 'O' rings and valves as well as the nylon stopcocks (of the syringes) were 
removed and washed in isopropanol and baked in a vacuum oven for 24 hours prior 
the cruise. The Niskin bottles were cleaned with isopropanol. The rubber bands 
on all bottles were replaced by stainless steel springs. The personnel for all 
water sampling and handling procedures at the bottles wore one-way gloves to 
protect the valves from grease. A standard gas (kindly provided by D. Wallace, 
IfM Kiel) was used to convert the ECD signal in concentrations. The CFC 
concentrations are reported in pmol kg-1 on the SIO93 scale (R. Weiss, SIO).


PERFORMANCE

The cruise was split into three legs. During the first leg (stations 1-12) 
mooring work were carried out, and the CFC system was not on board. On leg 2 
(stations 13-48), the Kiel CFC system worked continuously and a total of 410 
CFC-12 and 510 CFC-11 water samples were measured. The survey was dedicated to 
the circulation of the deep water masses. During periods of dense station 
spacing, sampling was focused on the water column below 800 m depth.

Accuracy of the data was checked by analysing 70 CFC-11 and 47 CFC-12 samples 
twice and the mean rms was 0.8% for CFC-12 and 0.6% for CFC-11 (Figure 1). The 
system and syringe blanks were checked by purging ECD clean Nitrogen 
permanently through 5 L seawater. The blanks were lower than 0.005 pmol kg-1 for 
both components. 

As no CFC poor water is available in the western subpolar North Atlantic, the 
Niskin bottle blanks could not be checked directly. On our cruises in the 
Northern Indian Ocean and the Tropical Atlantic, where CFC free deep water is 
available, the blanks of the precleaned bottles were lower than 0.003 pmol kg-1 
for both components (CFC-12 and CFC-11).

The temporal evolution of the ECD effciency is shown in Figure 2. During the 
cruise the effciency decreased about 20%. Major changes occured, when the 
drying agent (magnesiumperchlorate) in the purge and trap unit was exchanged or 
the molsieves had to be baked and therefore exchanged.

To correct the temporal drift, a calibration curve with 4-6 different standard 
gas volumes was carried out before and after each station, the change between 
these curves is thought to occur linear with time. As a typical example, the 
two calibration curves for station 20 are presented in Figure 3. CFC 
concentrations are calculated by using the two neighboured calibration points, 
assuming that the calibration curve is linear between these points.

At first we used sample volumes, precalibrated by the company (Machery and 
Nagel, Germany) for the analysis of standard gas. It turned out that these 
volumes could be off by more than 5%, affecting the precision of the measured 
oceanic CFC concentrations by the same amount. Therefore, in 1998, the volumes 
for the gas standard measurements (nominal 2 mL and 5 mL) were calibrated 
against two 'master' volumes by D. Wallace's group, who had done this task also 
for the CO2 community.

CFC measurements of the air inside the vessel and especially in the lab were 
carried out frequently in order to check for contamination. In general, the CFC 
concentrations in both places were only a few percent higher than in clean air. 
Clean air measurements were carried out occasionally by sampling air from the 
ship's compass bridge or forecastle.


PROBLEMS

From CTD profiles 14 to 21 the CFC-12 data could not be processed because of an 
unknown substance with a similar retention time than CFC-12. 

On the third leg, the CFC system malfunctioned and it was later found out, that 
the connection between the gas chromatographic column and the ECD was broken.


COMMENTS

The CFC-11 surface saturation relative to the atmospheric value of 266 ppt 
varied from 104-125% (Figure 4). The largest supersaturations were found off 
the shelf near Flemish Cap, they are correlated with a low salinity (Figure 5). 
These supersaturations are presumably caused by recent mixing of cold, fresh, 
and CFC rich water with warmer water from the south, while the air sea gas 
exchange had not enough time to equilibrate with the atmosphere. Such extreme 
values are observed in summer 1997, too [Körtzinger et al., 1999].

The CFC-11/CFC-12 ratio below 1000 m depth is 2.05 in the mean (Figure 6), 
which is similar to the observation made in summer 1997 during the Meteor 39 
cruise. 

In Figure 7 all CFC-11 concentrations measured during the cruise Valdivia 172 
are shown. In the upper 2000 m (the lower limit of the LSW) the values are 
about 4 pmol kg-1 . At larger depth (within the GFZW) the concentrations 
decreased to less than 2 pmol kg-1 and increased again near the bottom caused by 
CFC-rich DSOW.


REFERENCES

Bullister, J.L. and R.F. Weiss (1988). Determination of CCl3 F and CCl2 F2 in 
    seawater and air. Deep-Sea Res., 35, p. 839-853.

Körtzinger, A., M. Rhein, and L. Mintrop (1999). Anthropogenic CO2 and CFCs in 
    the North Atlantic Ocean - A comparison of man-made tracer. Geophys. Res. 
    Lett., 26, p. 2065-2068.



                               APPENDIX


THE STATION FILE 'VALDIVIA172.SUM' | THE BOTTLE FILE 'VALDIVIA172.SEA' 
   INCLUDES:                       |    INCLUDES:
-----------------------------------|-------------------------------------------
1  station number                  | 1  station number
2  year                            | 2  bottle number
3  month                           | 3  depth (dbar)
4  day                             | 4  in-situ temperature (°C)
5  hour: decimal minutes           | 5  salinity (psu)
6  latitude: decimal minutes       | 6  CFC-12 (pmol kg-1)
7  longitude: decimal minutes      | 7  CFC-11 (pmol kg-1)
8  water depth (m)                 | 8  WOCE quality flag for CFC-12 and CFC-11
9  depth of CTD profile (m)     
  
  
TECHNICAL INFORMATION  
-----------------------------------|-------------------------------------------
Gas chromatograph                  | Shimadzu GC 14
GC column                          | stainless steel, packed with Porasil C
Cooling trap                       | with Porapak T and Porasil C
Trap temperatures                  | -30°C, 100°C
Column temperature                 | 70°C, isothermal
ECD temperature                    | 300°C
Electron capture detector          | Shimadzu
Software for chromatogram analysis | Shimadzu CLASS LC 10 (1.63)
Standard gas                       | ALM 066676, D. Wallace, IfM Kiel
Precision                          | CFC-11: 3%,  CFC-12: 5%
Accuracy                           | CFC-11: 0.6%,  CFC-12: 0.8%
Blanks                             | negligible




WHPO DATA PROCESSING NOTES

Date      Contact     Data Type    Data Status Summary
--------  ----------  -----------  --------------------------------------------
02/14/00  Uribe       BTL          Submitted temp, salinity, CFC11 and CFC12
          Files from directory valdivia172 were moved from ftp-
              incoming.2000.02.14/
          This cruise took place July 14th - July 30th 1998.
          The data provided was temperature, salinity, CFC11 and CFC12.
          The expocode is 06AZ172.
          The doc file contained is M. Rhein's CFC report.
          All of the files are unformatted.
          Files were sent by Monica Rhein.
          Directory ar13_e/ar27 was created for this data.
          We have no records about who the Chi Sci for this cruise was.
                
12/22/00  Uribe       CFCs         Data Encrypted until released by M. Rhein
                
12/27/00  Buck        BTL/SUM/DOC  Submitted; unformatted; btl encrypted
          WHPO now has an unformatted sumfile, encrypted and unformatted BOT 
          file, and unformatted DOC file.  No PIs known for this cruise... This 
          data is nonpublic.
                
04/23/02  Lebel       CFCs         Final Data Submitted; still not public
          Regarding line:     AR13
          ExpoCode:           06AZ172
          Cruise Date:        1998/07/14 - 1998/07/26
          From:               LEBEL, DEBORAH
          Email address:      lebel@ldeo.columbia.edu
          Institution:        LDEO
          Country:            US
          The file:           valdivia172.dat - 78048 bytes
          has been saved as:  20020423.111843_LEBEL_AR13_valdivia172.dat
          in the directory:   20020423.111843_LEBEL_AR13
          The data disposition is:
               Non-Public  To Go Public?
          The file format is:
               Plain Text (ASCII) 
          The archive type is:
               NONE-Individual File 
          The data type(s) is:
               Other-final CFC data
          The file contains these water sample identifiers:
               Station Number (STATNO)
               Bottle Number (BTLNBR)
          LEBEL, DEBORAH would like the following action(s) taken on the 
          data:
               Merge Data
               Place Data Online
               Update Parameters
          Any additional notes are:
          These are the finalized CFC data for Valdivia 172 (06AZ172), 
            including the QUALT2 word.  Scale is SIO98, units are pmol/kg.  
          Data have yet to be made public by PI, Monika Rhein.
                

Date      Contact     Data Type    Data Status Summary
--------  ----------  -----------  --------------------------------------------
05/01/02  Bartolacci  BTL/SUM/DOC  Reformatting Needed
          btl: cfcs only; doc: pdf; SUM needs reformatting. BOT only 
          contains CFCs & needs reformatting. No CTD. DOC not ascii/r
                
04/03/03  Kappa       DOC          Final PDF/TXT Reports Compiled
          Previous online doc was a text version of the PI's pdf file. New pdf 
          includes figs & whpo-generated cruise track.  Both new reports (text 
          and pdf) include M. Rhein's cfc report (reformatted), whpo summary 
          page, and these data processing notes.
                
                
          
          
          


