Physical Environment
The important physical features of the Bering Sea are described in some detail
in U.S. GLOBEC Report 15 (U.S. GLOBEC, 1996). The following features are
particularly relevant to this implementation plan. We propose a program focused
on six habitats or biophysical domains on the broad, shallow eastern shelf with
the outer shelf and upper slope forming a seventh habitat (Fig. 7). Across the
shelf the domains are separated by a sequence of frontal systems: shelf-break,
middle, and inner or structural front. Circulation over the basin is
characterized by counter-clockwise flow with an eastern boundary current (the
Bering Slope Current at the shelf edge) (Fig. 8). Similar to conditions at
Georges Bank, tidal currents play an important role in generation of the two
shoreward fronts by mixing and generation of residual current by interaction
with topography. Over the middle shelf, mean currents tend to be insignificant,
whereas, moderate mean flow follows the bathymetry toward the northwest over the
outer-shelf. Alaskan Stream water flows into the Bering Sea from the North
Pacific primarily through Near Strait, Amchitka Pass and Amukta Pass (Fig. 9).
Over the shelf, seasonal ice cover greatly influences currents and water
property distributions, particularly that of temperature. Ice cover and its
related processes determine the southeastern extent and magnitude of the "cold
pool", a 40-50 m thick layer of water <2.0°C over the middle shelf, which
persists throughout the summer (Fig. 10). The cold pool likely influences the
distribution of biota on the shelf, and the ice extent influences the location
and timing of the spring phytoplankton bloom.
