Publication Date:
2022-05-26
Description:
This report summarizes the work, under the auspices of the WOCE Hydrographic
Programme (WHP), which took place on the R/V Akademik Vernadsky in June-July 1991.
The goal of the exercise was an international comparison/training cruise to obtain comparisons
of water sampling methods and analytical techniques employed by several groups for
the oceanographic measurement of salinity and oxygen in seawater. The training aspect
was formalized in a pre-cruise practicum held on board the vessel by Dr. Fred Culkin and
Mr. Paul Ridout of Ocean Scientific International, the manufacturer of IAPSO Standard
Seawater, At-sea comparisons of Russian Reference Water, manufactured in Moscow, were
made with IAPSO water. Further work involved comparisons of a Guildline and a pair of
SOKOL salinometers using reference water and natural seawater collected on the cruise.
While the agreement among the salnometers was quite good and at the level of acceptability
for the WHP, it was discovered that lack of thermal equilbration of the salinity
samples run on the SOKOLs led to substantial "errors" at large depths (or for cold water
samples). This could not have been anticipated before the cruise and would have been
missed in a shore-based or laboratory exercise. All five groups making oxygen comparisons
benefitted from the technical exchange afforded by the cruise and, as a result of reconciling
inter-group differences, have identified procedural changes they wil make in the future in
order to achieve the high standards required by the WHP, The technical interaction, which
amounted to "training" for all groups, was greatly facilitated by the cooperation of Captain
Malnovsky, Chief Scientist Panteleyev, the scientists from MHI, Sevastopol, and the
crew of the Vernadsky.
On the Vernadsky comparison cruise, a shore-based practicum was held prior to
sailing in order to review the theory and measurement of salinity. The cruise itself, which
took place between 27 June and 8 July 1991, was in the NE Atlantic to the west of Madeira.
An international group of experts in salnity and oxygen measurements was drawn from the
United Kingdom (UK), Spain, Russia, Ukraine, and the United States (US).
Except for one of the five groups, measured oxygen values in the range of 3-5 mIll
(concentration units are used throughout) agreed with one another within :11%, which
exceeds the WOCE requirements by a factor of 2. Subsequent analyses of the differences by
all five groups could account for much of the observed inter-group variations, Intra-group
precision was generally in the range of 0,1-0.4%, As a result, of a low oxygen sparging
experiment in which sample oxygens 0: 1.2 mIll were generated, substantial inter-group
differences of :1.08 mIll were found indicating that oxygen specifications for WOCE need
to be expressed as both a percent "error" and a low oxygen bias.
The salinity comparison component of the cruise enabled comparison of various
batches of Russian Reference Water (RRW) of various salnities (10, 20, 30, 35 and 40)
against IAPSO Standard Seawater (SSW) of various salinities (10, 30, 35 and 38); inferences
could then also be drawn on the relative performance of the two types of salinometer
(Guildline Autosal 8400 and SOKOL 4602) used during the experiment. Under quasilaboratory
conditions, the machines produced mean results different by no more than 0.001
in salinity for salinity 35 RRW, standardizing against salinity 35 SSW. The other salnities
produced less conclusive results, but the three salinometers deviated by no more than
0.003 from the expected value over a wide range of salinities. Under operational conditions
(analysis of duplicate samples collected from CTD casts) a mean bias emerged between
machines of approximately 0.005 in salinity (SOKOL fresher than Guildline), Subsequent
investigations tentatively ascribed this bias to non-equilbration of deep (cold) samples in
the Russian system.
Description:
Prepared for the National Science Foundation under Grants
OCE89-07815, and OCE92-06184, T. Joyce, Principal Investigator;
Vetlesen Funds, Woods Hole Oceanographic Institution; and with
support from the Intergovernmental Oceanographic Commission.
Keywords:
Vernadsky (Ship)
;
World Ocean Circulation Experiment
;
Oxygen
;
Salinity
;
Oceanography
;
Measurement
Repository Name:
Woods Hole Open Access Server
Type:
Working Paper
Format:
3230770 bytes
Format:
application/pdf
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