Russian Journal of Marine Biology, Vol. 31, Suppl. 1, 2005, pp. S1–S8.
Original Russian Text Copyright © 2005 by Biologiya Morya, Melnikov.
1063-0740/05/3101-S © 2005 Pleiades Publishing, Inc.
Sea ice cover is a key component of the Arctic
Ocean ecosystem. Being an interlayer between two dif-
ferent physical media—water and air—ice is important
in maintaining the thermodynamic equilibrium
between the ocean and the atmosphere as a result of the
change in its mean equilibrium thickness, and the equi-
librium of this system is maintained and determined by
the stability of the Arctic climate . During the last
two decades, there has been a clear temperature trend
toward warming. The warming has brought about a
marked reduction in the area and thickness of the ice
cover, a rise in temperature, and a freshening of surface
arctic water [13, 21, 28, 32]. The changes in the climate
and the ice environment have caused alterations in the
composition and structure of biological communities
inhabiting sea ice and under-ice surface arctic water
[24–26]. The reason for these alterations is the variation
of hydrophysical and hydrochemical characteristics of
surface water contacting the sea ice cover. Thus, over
the last two decades, average salinity at depths from 0
to 30 m decreased by 4‰ and temperature increased by
The main aim of this study was to show how the eco-
systems of sea ice and the under-ice water layer
respond to global changes in the Arctic. To this end, we
analyzed the composition, structure, and functioning of
the sea ice–upper ocean ecosystem. By the upper ocean
we mean the mixed water layer 0–30 m above the ther-
mocline, whose characteristics and dynamics are linked
with the sea ice cover.
For comparison, we used materials collected over an
interval of two decades in the anticyclonic Arctic Gyre
at the ice stations Severnyi Polyus-22 and 23 (SP) in
1975–1981  and at the SHEBA (Surface Heat Bud-
get of the Arctic Ocean) in 1997–1998 [19, 24, 25, 27].
CTD proﬁles obtained from the AIDJEX ice station that
drifted in the anticyclonic Arctic Gyre in 1975–1976
 were also used. Results of comparison of the key
ecosystems are discussed in two sections: the ﬁrst deals
with the sea ice ecosystem and the other with the upper
SEA ICE ECOSYSTEM
Area, Extent, and Thickness of Ice Cover
In the late seventies of the last century, the area of the
Arctic sea ice cover at its maximum was 8260000 km
(March) and at minimum 6900000 km
; i.e., ice loss during summer ice melting was
The Arctic sea ice cover is nonuniform in its compo-
sition. The central deep Arctic basin is permanently
occupied by thick perennial ice (more than 80% of the
area), while shallow fringing seas are covered by sea-
sonal ice, which is formed in winter on open water
Sea Ice–Upper Ocean Ecosystems
and Global Changes in the Arctic
I. A. Melnikov
Institute of Oceanology, Russian Academy of Sciences, Moscow, 117997 Russia
Received May 25, 2004
—In the Arctic, a clear temperature trend toward warming has been observed during the last two
decades. The warming has led to a reduction in the area and thickness of the Arctic sea ice cover because of
increased melting. Melt water is accumulated within the 0- to 30-m surface layer, markedly changing its hydro-
logical and hydrochemical characteristics: this water is warmer and fresher, with lower nutrient concentrations.
A stable thermocline at depths of 30–35 m weakens vertical mixing of water and hampers active exchange
between nutrient-enriched water lying below the thermocline and nutrient-poor water under ice. This affects the
qualitative and quantitative composition of upper-ocean phyto- and zooplankton. The changes in the climate
and the ice environment cause marked alterations in the composition and structure of the biological communi-
ties of sea ice and under-ice surface water. Comparative analysis of materials collected in the anticyclonic Arctic
Gyre at the ice stations Severnyi Polyus-22 (1975– 1981) and SHEBA (1997–1998) shows that over the last two
decades the number of species of ice diatoms markedly decreased and the role of freshwater algae increased.
The number of nematodes, copepods, amphipods, and turbellarians, which were the dominant groups in peren-
nial ice, also declined sharply. The results suggest that the sea ice–upper ocean ecosystem is changing from typ-
ically marine to brackish-water. The main reason for these changes is probably global warming in the Arctic.
Arctic Region, sea ice, climate, change, biota.