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030696B.CHM + Source: ONR Asia +
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Contributory Categories: BIO, PHY
Country: Japan
From: International Workshop on The Okhotsk Sea and Arctic
The Physics and BioGeochemistry implied to the Global
Cycles (Influence of Sea Ice on Climate and Marine
Ecosystems) 29 Feb. - 1 March 1996, Tokyo, Japan
KEYWORDS: Japan, Sea of Okhotsk; Isotopes, Tracers, Water Masses
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Items 1-3 this message, Items 4-5 next message
Item 1
CHEMICAL OCEANOGRAPHY OF OKHOTSK SEA
by
C.S. Wong
Ocean Biogeochemistry
Institute of Ocean Sciences
P.O.Box 6000, Sidney, B.C.
Canada V8L 4B2
Chemical oceanography of Okhotsk Sea was studied by the
Institute of Ocean Sciences in Sidney, B.C. Jointly with the
Pacific Oceanological Institute in Vladivostok, Russ a, using the
MV Nesmeyanov along WOCE Line PIW starting in the Pacific Ocean
near Bussol' Strait in the Kuril Island, crossing the basin and
shelf regions of the Okhotsk Sea and terminating near the city of
Okhotsk on the Siberian shore, during the period August
30-September 21, 1993. Okhotsk Sea has two major basins: the
shallower Deryugin Basin to a depth of about 1,500 m and the
deeper Kuril Basin to 3,500 m. The blogeochemical and
oceanographic processes are different in these basins.
The Okhotsk Sea is a marginal sea bounded by land on three
sides and the Kuril Island chain, separating it from the
subarctic North Pacific, with connection to the salty Japan Sea
through two shallow straits, the Soya Strait (40 m sill depth)
and the Tartar Strait (100 m sill depth) and to the fresher North
Pacific through two deep straits, the Bussol' Strait ( 2300 m
sill depth) and the Kruzenshtema Strait (1900 m sill depth). The
chemical properties of the Okhotsk Sea are affected by the water
exchanges with the salty Japan Sea waters, the large gross
exchange of 15 Sv with the North Pacific through the deep
Straits, formation of the Okhotsk Sea shelf waters during winter
ice formation and the mixing of inflowing North Pacific waters to
produce the North Pacific Intermediate Waters (Wong et al.,
1995). The physical oceanography of the WOCE Line PI W was
described in Howard et al. (1995).
For the 1993 WOCE sections in Okhotsk Sea, water samples and
CTD casts were obtained using a General Oceanics Rosette with 10
L. Niskin PVC samplers. The measurements included temperature,
salinity, dissolved oxygen, dissolved nutrients (phosphate,
nitrate and silicate) and chlrofluorocarbons F- I I and F- 12
following procedures outlined in the WOCE protocol (WOCE, 1994).
JGOFS Global C02 Survey was conducted also on the same WOCE
expedition with shipboard measurements of dissolved inorganic
carbon (DIC) done by colilometry and total alkalinity (TA) by
potentiometric titration with techniques described in Dickson and
Goyet (1994). Some selected sections are
shown:temperature, hydrocast salinity, dissolved nitrate,
phosphate. ilicate, oxygen, dissolved inorganic carbon,total
alkalinity, freon F-11 and freon F-12.
Freons distribution showed high concentrations of over 6
pM/kg for F-11 and over 3 pM/kg for F12 in the subsurface shelf
waters above 200 in in the shallower portion of Okhotsk Sea at
latitudes 56 - 58 degs. N, and also in the open waters over the
Derugin and the Kuril Basins. The high freons were acquire d by
the shelf waters due to the much higher solubility of freons in
seawater at low temperature in pre-winter condition although not
dense enough to sink below 200 m. The winter waters dense enough
to sink as a plume would be mixed with surrounding waters
forming a shelf-derived water (SDW). This SDW would mix
isopycnally for sigma-theta) 26.8 to 27.2 with the North Pacific
water entering Okhotsk Sea through Kruzenshterna Strait to
produce the Sea of Okhotsk Intermediate Water (SOfW). Using CFCs
concentrations of SDW, OSIW and NPW at 6,5, 3 and 2.75 pM/Kg
respectivelly, the export of Okhotsk Sea Intermediate Water was
estimated to be about 5 Sv out of Bussol' Strait as a significant
contribution to the North Pacific Intermediate Water, which is
about 15 Sv.
Distributions of physical and chemical properties with depth
show a marked difference between Okhotsk Sea and the North
Pacific. In the upper 1,000 m, Okhotsk Sea has lower potential
temperature, salinity and nutrients, but higher freons and oxygen
than the North Pacific. Below 1,000 m to about 2,000 m, Okhotsk
Sea is dominated by a warmer and fresher Deep Water, Below 2,000
m, both Okhotsk Sea waters in the deep Kuril Basin and the North
Pacific deep waters have the same physical and chemical
characteristics
The biogeochemical processes In the Okhotsk Sea basins
result in different distribution patterns in the biogenic
properties in the water columns. High accumulation of dissolved
silicate. nitrate and phosphate, dissolved inorganic carbon (also
partial pressure of C02), but lower oxy-en (,i.e. higher A.O.U.,
apparent oxygen utilization) suggest that active biology in the
upper ocean during the summer period led to such
distribution mainly in the Deryugin Basin, in contrast to the
Kuril Basin. Seasonal studies would be necessary to understand
the blogeochemistry of the Okhotsk Sea, an important area of
blogenic accumulation influenced by the complex circulation and
seasonal ice formation in the upper ocean.
REFERENCE:
Wong, C.S., R.J. Matear, H.J. Freeland, F.A. Whitney and A.S.
Bychkov, Chloroflurocarbons in the Sea of Okhotsk: The role
of the Sea of Okhotsk Intermediate Water in the formation of
North Pacific Intermediate Water. Submitted to Journal of
Geopkysical Research. 1995.
Freeland, H.J.,m A.S. Bychkov, F.A. Whitney, c. Taylor, C.S.
Wong and G.I. Yurasov, An oceanographic survey through the
Sea of Okhotsk: WOCE Survey Line PIW. submitted to Journal
of Geophysical Research. 1995.
World Ocean Circulation Experiment. WOCE Operations Manual.
Vol 3, Section 3. 1, Part 3.1.3. WHP Operations and
Methods. WOCE Report No. 68/9 1. November 1994.
Dickson, A.G. and C. Goyet. Handbook of methods for the
analysis of the various parameters of the carbon dioxide
system in sea water. Version 2. U.S. Department of Energy ,
1994.
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End Item 1
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Item 2
NORTH PACIFIC INTERMEDIATE WATER STUDIED WITH
CHEMICAL TRACERS:
IS IT ORIGINATED IN THE OKHOTSK SEA?
Shizuo Tsunogai and Takayuki Tokieda
Marine and Atmospheric Geochemstry Laboratory
Graduate School of Environmental Earth Science
Hokkaido University
Recently the North Pacific Intermediate Water (NPIW) has
been paid much attention. This is due to its significant role as
a sink of anthropogenic carbon dioxide. Some studies have
claimed that the source region of the NPIW is the Okhotsk Sea.
To examine this claim, we have studied the NPIW with chemical
tracers, although we could not get samples within the Okhotsk
Sea. The chemical tracer used are chiefly CFCs which can be used
as tracers of waters formed after 1960's and we have also
utilized some other chemical tracers such as tritium, C-14 and
dissolved silicate.
The horizontal and vertical distributions of CFCs were
consistent with those of excess total inorganic carbonate of
anthropogenic origin. Their concentrations in the surface water
are certainly almost saturated and decreased with depth. They
were higher in the western part of the North Pacific around 40'N
than in the central (and, of course, the eastern) part of the
North Pacific in the subsurface water. The maximum penetration
depth exceeded 1000 in depth or the surface of (sigma theta of
27.2 in the western North Pacific. It, however, is interesting
to note that the old water mixed with the newly formed NPIW is
extremely old. In other words, the NPIW is formed by the mixing
of cold surface water the deep water.
Similar results were obtained from other chemical tracers.
For example, the maximum concentration of artificial C-14 in the
upper NPIW was found in the latitudinal belt of 40 - 45'N in the
western North Pacific.
We do not support the idea that the main source region of
the NPIW is the Okhotsk Sea. This is due to the following two
facts. One is that the maximum concentration of CFCs -at the
isopycnal surfaces of the amount of the NPIW estimated from the
distribution of CFCs, which is too much to be expected from the
cooling within the Okhotsk Sea.
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End Item 2
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Item 3
AN ISOTOPIC STUDY ON SEA ICE IN THE SEA OF OKHOTSK
Jinro Ukita
Dept. of Earth and Planetary Physics
Faculty of Science
University of Tokyo
Noriyuki Tanaka
Graduate School of Earth and Environment Science
Graduate School
Hokkaido University
Toshlyuki Kawamura
Institute of Low Temperature Science
Hokkaido University
ABSTRACT
The Sea of Okhotsk is a marginal sea adjacent to Pacific Ocean
through straits in Kuril Islands, and surrounded by land on three
sides; the Kamchatka Peninsula, the Asian continent, and Sakhalin
Island. Despite its relatively southern location, its climate is
characterized by sea ice in winter when the east-west air
pressure gradient associated with Siberian high and Aleutian low
results in southward migration of ice that starts in the
northwest region of the Sea of Okhotsk. Although this is
conjectured earlier by Watanabe (1963), it is only recent that
this southward transport of sea ice off Sakhalin Island was
confirmed by using the drifting tracks of ARGOS buoys deployed on
ice floes (Mochizuki et al, 1995). Besides this general motion,
we have very limited information about sea ice formed in the Sea
of Okhotsk. Hardly have we -any knowledge about
freezing, transport, and melting of sea ice in the region. In an
attempt to answer these questions, we conducted isotopic,
salinity, and density analyses on sea ice swnples taken from the
Sea of Okhotsk
On January 27 and 28, 1995, ice sampling was conducted by
the Japanese Maritime Safety Agency's ship So-va. The first floe
sample (Sample A) was taken very close to the ice edge where ice
concentration was 10 - 20 %, and the second floe sample (Sample
B) was collected on the following day from an interior area of
the ice pack with ice concentration of 80 - 100 %. Then we
analyzed the samples using a method similar to the one described
by Tucker et al. (1987).
Considering the fact that one was taken just a day earlier
from the location only 30 - 40 km way, these two Ice Iloes have
distinctive features; Sample A with the granular structure and
Sample B with the broken columnar structure. The granular
feature found in Sample A may be attributed to low ice
concentration, which favors for the production of frazil ice by
the rough ocean surface condition. On the other hand, Sample B
came from an interior area with high ice concentration, which
favors for the production of columnar ice and a high level of
ridging and rafting activities. They taken togethei account for
the broken columnar structure with random orientation of columns
found in Sample B.
The salinity and density minima along with the abundance of
bubbles and opaqueness observed in the top part of Sample A
(Figure 1) first led us to believe that this has the snow
origin. If this were the case, we can approximately identify the
location of its origin from the empirical relationship that
exists between isotopic values of precipitation and air
temperature (Dansgaard, 1964; Yurtsever, 1975). On the
contrary, observed isotope values are substantially higher than
the values expected for the snowfall in the Sea of Okhotsk.
Typically, an analysis based on the salinity and isotope budget
is used to identify the source for-an ice-sea water system
(Ostlund and Hut, 1984; Lange et aL, 1990, Macdonald et al.,
1995). However, such an analysis fails in this case with
unproportionally low density and salinity and high dl8O. The
conventional analysis assumes the isotopic fractionation factor
for frazil ice is the same as that of sea ice that is formed
under relatively quite environment. Thus to clarify the
interpretation of the present sample, it seems necessary to
conduct basic laboratory and field experiments to estimate the
isotopic fractionation factors during the frazil ice production
and its dependence on physical environment.
In summary, the results from the present analysis suggest
the systematic dependence of crystallographic structures on ice
concentration and the necessity and importance-of a new
experiment for the fractionation factor for frazil ice.
REFERENCES
Dansgaard, W., 1964: Stable isotopes in precipitation. Tellus,
16, 436-468.
Lange, M. A., P. Shlosser, S. F. Ackley, P. Wadhams, and G. S.
Dieckmann, 1990: 18O concentrations in sea ice of the Weddell
Sea, Antarctica. J. of Glac., 36, 315-323.
Macdonald, R.W., D. W. Paton, and E. C. Carmack, 1995: The
freshwater budget and under-ice spreading of Mackenzie river
water in the Canadian Beaufort Sea based on salinity and
180/160 measurements in water and ice, J. Geoph-vs. Res., 100,
995-919.
Mochizuki, S., T. Takatsuka, T. Aota, and P. Tuskov, 1995:
Tracing of ice floe in Sea of Okhotsk by satellite-tracked
drifters. Abs. on the Tenth Intemational Symposiuni on Okhotsk
Sea, Sea Ice and People, The Okhotsk Sea and Cold Ocean
Research Association. Monbetsu, Hokkaido.
Ostlund, H. G., G. Hut, 1984: Arctic ocean water mass balance
from isotope data. J. Geophys. Res., 89, 6373-638 1.
Tucker, W. B., A. J. Gow, and W. F. Weeks, 1987: Physical
properties of summersea ice in the Fram Strait. J. Geophys.
Res., 92, 6787-6803.
Yurtsever, Y., 1975: Worldwide survey of stable isotopes in
precipitation, Rep. Sect. Isotope Hvdrol., IAEA, 40 pp.
Watanabe, K., 1962: Drifted velocities of ice measured from air
and separately computed values of their wind-induced and
current-induced components - study on sea ice in Okhotsk Sea
(11). 7he Oceanographycal Magazine 14, 29-4 1.
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End Item 3
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