Dutch JGOFS - Dissolved oxygen measured during the North Atlantic Pilot Project (Leg 3)

The North Atlantic Pilot Project (NAPP), also known as the North
Atlantic Bloom Experiment (NABE), was the first field work of JGOFS
(Joint Global Ocean Flux Study) and it served as pilot study for the
proposed North Atlantic Process Study. Six countries participated in
this study: Canada, France, Germany, The Netherlands, UK and USA.

The Netherlands contributed to NAPP with four cruises on board
R.V. Tyro:
1. Leg 1, 31 July-11 September 1989 (Upper Ocean Processes)
2. Leg 2, 13-28 September 1989 (Benthic Processes)
3. Leg 3, 17 April-31 May 1990 (Upper Ocean Processes)
4. Leg 4, 2-29 June 1990 (Benthic Processes)

The following oxygen data set originated during Leg 3. Dissolved oxygen
was measured according to the high precision Winkler titration method
developed by Tijssen (Hartwig and Michael 1978, Tijssen 1989, Williams
and Jenkinson 1982). Over 900 oxygen samples were taken at 16 stations
from depths of 5 m until more than 4000 m. From each depth, duplicate-or,
if time and the amount of water available allowed it, triplicate samples
were taken. It was attempted to lead the water through a 200 micron
zooplankton filter first. However, duplicate values were less accurate
after that. At all stations from 2 depths seawater blanks were taken and
analyzed. The mean value is 0.77 microMol/m3. There is no trend to be
seen in the value of seawater-blanks from 33N to 60N. Immediately after
sampling the reagentia were added while in a separate bottle the "sample
temperature" was measured. Before starting each titration the temperature
of the thiosuolphate solution was measured. Data are corrected (salinity)
as to arrive at the reported micromol/kg. Differences between the values
of the duplicate/triplicate samples are generally smaller than 0.5 micro
mol/kg.

Hartwig, E.O. and J.A. Michael (1978). A sensitive photoelectric Winkler
titrator for respiration measurements. Environmental Science & Technology
12(6): 712-715

Tijssen,S.B. (1981). Anmerkungen zur photometrisched Winkler.
Sauerstofftitration und ihre Anwendung zur Schatzung der Primarproduktion
im Meer. In: III Internationales mikorbiologisches Symposium, Smolenice,
3-6 Juni 1980. Editor L. Daubner. Veda, Verlag der Slowakischen Akademie
der Wissenschafter, Bratislava 1981.

Williams, P.J. LeB, and N.W. Jenkinson (1982). A transportable micro-
processor controlled precise Winkler titration suitable for field station
and shipboard use. Limnol. Oceanogr. 27(3): 576-584