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.

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