Sea Ice
-- Sea Ice --
Sea Ice Characteristics across the Arctic Ocean
Walter Tucker, Anthony Gow, Hazen Bosworth,
Erk Reimnitz and Debra Meese
The Arctic ice cover separates the ocean from the atmosphere, so it is a key
component in the exchange of heat, mass and momentum between the two.
The properties of the ice cover in summer are especially important, as this is
the period of maximum solar radiation. During summer the ice properties
become extremely variable, having changed from a highly compact, reflective
snow-covered surface during winter and spring to a mottled surface consisting
of melt ponds, bare ice and deteriorating snow with many open leads. Major
changes occur in the overall surface albedo, the ice cover warms accompanied
by draining brine and melting ice, and incorporated sediment and contami-
nants can be released. The amount of light penetrating into the ocean stimu-
lates biological activity, because a major part of the Arctic Ocean food chain is
within a few meters of the ice.
The ice characterization component of AOS-94 consisted of surface albedo
measurements, melt pond characterization, snow depth surveys, aerial photog-
raphy surveys, ice-borne sediment sampling and ice coring. Ice cores were
used for thickness, salinity, temperature, chemistry and structural analyses,
and samples were provided to associates for stable isotope measurements.
Visual observations and satellite imagery obtained on the section indicated
that the concentration of ice increased rapidly from 5070% south of 72N
to 90100% for the remainder of the section until the marginal ice zone in
the Eurasian Arctic was reached. Ice thickness also increased with northward
progress from about 1 m in the first-year ice of the southern Chukchi Sea to
about 2.7 m at the North Pole, as verified from visual observations and ice
core measurements. With the exception of three ice cores obtained in the
Chukchi Sea, all cores on the section were collected from second-year or multi-
year ice. The cores revealed thermally degraded ice near the surface above the
water level and extremely well drained ice below. Temperatures of the ice were
consistently near zero at the surface, increasing linearly to about 1.5C at the
icewater interface. Salinities were also consistent with previous measurements
of summer sea ice (Tucker et al. 1987, Eicken et al. 1995), being zero at the
Walter Tucker, Anthony Gow, Hazen Bosworth and Debra Meese are with the U.S. Army Cold Regions Research
and Engineering Laboratory in Hanover, New Hampshire, U.S.A. Erk Reimnitz is with the U.S. Geological
Survey in Menlo Park, California, U.S.A.
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