Sea Ice
respectively), probably due to higher concentrations of foraminifera on the
sea floor. The visual estimates of sediment on the ice surface would indicate
that the amount of sediment being transported by the ice is small, yet because
it was observed across most of the Arctic Ocean, it is capable of transporting
and redistributing shelf sediments across the entire Arctic Basin.
A primary objective of the detailed ice-sediment study was to determine if
radiocesium was present within the ice-entrained sediment. In the ice-borne
sediments, 137Cs activities ranged from 4.9 to 73 Bq/kg (dry weight). Many
of the samples had 137Cs activities exceeding those found in benthic sedi-
ments in the deep basins or the shelves of the Beaufort, Chukchi or Bering
Seas, though the levels are far too low to be of concern to health. The highest
value (73 Bq/kg), found north of the Chukchi Sea, is comparable to levels
present in the sediments of the Yenesey and Ob River estuaries and the Kara
Sea. However, the three-year reverse trajectory indicated that the source area
for this parcel of ice was the offshore Banks Island region. Since there is no
known source in the Banks Island area, either the ice parcel was far older than
three years and had been incorporated elsewhere in the Beaufort Gyre or the
trajectory calculation neglected the possibility of easterly transport along the
Siberian shelf. Another remote possibility may be that radiocesium levels are
enhanced during the process of sediment entrainment into ice.
REFERENCES
Eicken, H., M. Lensu, M. Lepparanta, W.B. Tucker III, A.J. Gow and O.
Salmela (1995) Thickness, structure, and properties of level summer multi-
year ice in the Eurasian sector of the Arctic Ocean. Journal of Geophysical
Research, 100: 22,69722,710.
Jeffries, M.O., K. Schwartz, K. Morris, A.D. Veazey, H.R. Krouse and S.
Cushing (1995) Evidence for platelet ice accretion in Arctic sea ice develop-
ment. Journal of Geophysical Research, 100: 10,90510,914.
sion by spatially complex and temporally varying sea ice covers. Journal of
Geophysical Research, 95: 9,5579,567.
Tucker, W.B. III, A.J. Gow and W.F. Weeks (1987) Physical properties of
summer sea ice in the Fram Strait. Journal of Geophysical Research, 92: 6,787
6,803.
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