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030796B.CHM  + Source:  ONR Asia +
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Contributory Categories:

Country:  Japan, USA 

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, Bering Sea; Isotopes, Sediment
traps, nutrients

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Items 4-5 this message, Items 1-3 previous message

Item 4

INORGANIC RADIOCARBON (14C) IN TIME-SERIES SEDIMENT TRAP
SAMPLES FROM THE SEA OF OKHOTSK AND THE BERING SEA

                              Makio Honda
               Japan Marine Science and Technology Center


     Time-series sediment trap experiment reveals the seasonal
variability in the process of biogenic and lithogenic material's
transport. Organic and inorganic carbon flux give us a lot of
information concerning biological activity and carbon cycle in
the upper ocean. In addition, these carbon flux, which are
assimilated or calcified in the euphotic layer, must record
isotopic information of dissolved carbon in the ambient sea
water.  In order to study seasonal variability in dissolved
inorganic 14C in the euphotic layer, inorganic 14C in time-
series sediment trap samples from the Sea of Okhotsk and the
Bering Sea was measured by NOSAMS at WHOI.
     Inorganic D14C values in nine sediment trap samples
representing spring, fall and winter seasons were negative, which
values were from - 48 to - 12 permil and from - 60 to - 21 per
mil in the Sea of Okhotsk and the Bering Sea, respectively.       
     These values are approximately 25 permil smaller than those
in the surface water from Bering shallow water observed during
GEOSECS Pacific expedition (1972-73).  Our sediment trap
experiment was carried out in the early 1990's and 20 years have
passed since GEOSECS expedition.  Our negative values can be
explained by the decrease of bomb-produced D14C in the
atmosphere and the upper ocean.  In addition, inorganic D14C
varied seasonally: D14C in fall season were generally higher than
other seasons and the difference in D14C between fall and winter
were approximately 30 permil.  Assuming the seasonal change of
mixed layer thickness and using GEOSECS carbonate data from the
Bering Sea, simple box model calculation was done to interpret
the difference in D14C.  Based on the model, seasonal change of
thickness of the mixing layer may contribute to the seasonal
change of D14C in the surface water, and in turn that in settling
particle.  Although there are some uncertainty remaining, our
study suggests that 14C values in time-series sediment trap
samples can be used for the certification of the seasonal
variability in 14C in the upper ocean caused by the change of
mixed layer and C02 exchange between the atmosphere and the
ocean.
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End Item 4
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Item 5

CHARACTERISTICS ON THE DISTRIBUTION AND COMPOSITION OF NUTRIENTS 
IN THE OKHOTSK SEA

Yoshiaki MAITA
                   Faculty of Fisheries
                   Hokkaido University
                   Minatocho Hakodate 041
                   Japan

                               Abstracts
  The characteristics of nutrient concentrations and their
compositions were examined for four types of water masses found
in the southern Okhotsk sea, i.e.,Soya warm waters, surface low
salinity waters, intermediate cold waters, transition and warm
deep waters (Aota 1979).  In these water masses, the
intermediate cold water is especially significant for biological
production from the nutrient concentrations and relative
elemental composition point of view.
   It was observed that the low temperature core having high
nutrient concentrations was existent at the surface euphotic
layer in the near coast of Hokkaido of the Okhotsk Sea in summer
seasons.  This is caused by intrusion of the intermediate cold
waters into surface layers.  This means that high new production
are maintained by continuous supply of nitrate nitrogen in the
southern Okhotsk Sea. 
     Primary productivity regime will -be also discussed about
the correlation between chlorophyll a concentration and atomic
ratios of Si02-Si/NO3-N referring to the data from the northern
North Pacific and the Bering Sea.
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End Item 5
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