Marine Ecosystems Research Department - jamstec japan agency ...

JAMSTEC 2002 Annual Report
Frontier Observational Research System for Global Change
) Observation of Arctic surface water via mooring
buoys
) Development of a database compiling Arctic Ocean
chemical composition data
During the observational cruise of the R/V Mirai in
FYs , and , the water samples for isotopic
composition analysis were collected in the
Beaufort Sea. From the analytical results, riverine and
ice melt water distributions were estimated and it
became clear that both the river-origin and ice melt
waters contributed to the decrease in salinity of surface
water (stratification) to similar degrees. A comparison
of the results of FYs , and part of
results of FY show that the distribution pattern of
these two types of water showed significant difference
in terms of oceanic structure both horizontally and
vertically year by year, which implies that the high
oceanic variability is due to the complexity in the
freshwater distribution pattern. Ba, which is a tracer
for river water from the North American continent, is
also measured at Hokkaido University.
The analytical results of Ba revealed that approximately
half of its amount was removed from seawater
by biological activity, thus casting doubt on the
preservability of the element, which is an important
property for a water mass tracer. The removal ratio in
Ba/Si from surface seawater was found to be . to .
and substantially larger than other oceans where the
ratio is approximately .. The larger removal ratio
could be attributed to biogenic precipitation of Ba and
subsequent removal, which is presumably also related
with brine in frozen sea ice. A preliminary analysis of
Ba in ice reveals enrichment of Ba compared with surrounding
seawater (Fig.).
The response of the Arctic Ocean to external forcing
such as atmospheric disturbance has been monitored
by a mooring system with MMP in Canada
Basin. Another new mooring system with MMP was
also deployed in the Laptev Sea (Fig.). The mooring
system in Canada Basin was retrieved for data recovery
and redeployed at the same location. The preliminary
analysis of the data showed unexpected high frequency
response of the Arctic Ocean almost throughout
the water column. The results are expected to give
us clear pictures on energy dissipation in the ocean
and to contribute to the improvement in accuracy of
the Arctic Ocean model. With regard to the data set
construction, data processing for the Bering Sea,
Greenland Seas, etc is now under way.
-0.50
-1.00
y = -0.93581 -0.082362x R = 0.99221
O-18
80
70
140
120
Ba
n-Ba
-1.50
60
50
100
80
O-18
-2.00
-2.50
40
30
20
Ba
Ba
60
40
-3.00
Ba
10
20
-3.50
0
0
0 5 10 15 20 25 30 0 5 10 15 20 25 30
Salinity
A
Salinity
Fig.17 AO 18 and Ba vs. Salinity. AlthoughO 18 (red open circles) shows simple mixture of
sea ice and surrounding seawater, Ba(closed circles) shows significant enrichment with
increase in seawater fraction deduced by salinity. BNormalized Ba (n-Ba) to the salinity
of 30 psu vs. salinity. This shows relative degree of enrichment of Ba in sea ice.
B
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