0
the Trans Polar Drift, which carries surface
water from Siberia across to Greenland. The
1000
137Cs and 134Cs/137Cs identify the source
as European reprocessing plants and Cher-
2000
nobyl fallout and indicate that the late-1970s
peak of Sellafield-labeled water has now
passed over the central Arctic Ocean, approx-
3000
imately 15 years later. A comparison of the
137Cs profile measured at the North Pole to
LOREX (1979)
O
4000
profiles measured in 1979 and 1991 illus-
A den (Sta. 173, 1991)
trates the history of the transport. In 1979
OS (Sta. 35, 1994)
137Cs mainly
the water column contained
5000
0
4
8
12
16
20
derived from atmospheric fallout, before the
137
Cs (Bq/m3)
Chernobyl accident and before effluent from
European reprocessing plants had reached the Atlantic layer of the central 137Cs profiles meas-
Arctic Ocean. A large increase in the 137Cs inventory in surface waters by urold at 1he 9,oirth
e
t N
P e in 97 n
1991 and 1994 was caused by the arrival of Sellafield and Chernobyl 137Cs. 1991 and during
The 137Cs levels below 1000 m are not significantly different from those meas- AOS-94.
ured in 1979, indicating the continued maintenance of a pronounced Sella-
field signal at this depth since 1979. The results from the sediment analysis
indicate that the shelf slope sediments of the Chukchi Sea contain the highest
inventory of artificial radionuclides, while the central Arctic areas have the
lowest inventories.
Preliminary results provide little evidence of radioactive contamination of
the Arctic Ocean from Russian sources. However, the transport pathways of
potential contaminants can be delineated through studies of tracers from Euro-
pean reprocessing plants. Although the magnitude of the artificial radionuclide
signal measured in the Arctic Ocean may be a factor of ten greater than levels
due to atmospheric nuclear tests, these levels are significantly lower than levels
that would constitute a radiological threat to organisms or humans along the
North American coast.
61
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