While our knowledge of the physical oceanography of the Bering Sea has expanded greatly over the past few decades, many phenomena exist which are not understood primarily because observations are limited or do not exist. That a vast percentage of the Bering Sea lies within the domain of two different nations has not facilitated research programs that could provide the needed observations. Further, while the eastern continental shelf continues to have ongoing research programs and interest in the role of physical processes over the western shelf is growing, the deep basin remains largely unexamined.
The Bering Sea is a vital part of the general circulation of the North Pacific Ocean; fluxes of heat, salt, nutrients, and other dissolved constituents and planktonic material are exchanged through the passes. Primary questions, however, remain about the variability, magnitude and mechanisms influencing transport through the Aleutian Passes. In contrast, the flux northward through Bering Strait, which is important to conditions on the Arctic shelves and ocean, is relatively well described and understood.
While it is recognized that flow through the passes is a primary source of circulation within the basin, many questions remain regarding the current systems of the Bering Sea. What is the nature of the annual signal of the ANSC, and if there is a significant annual signal, does it occur in both speed and transport? The BSC apparently can be characterized by two modes, yet the phenomena that generate these are not known. While some studies have elucidated the nature of the Kamchatka Current, little is know of the temporal variability in transport and eddy kinetic energy. What is the magnitude and variability of inflow of DPW into the Bering Sea Basin? The flow patterns of the deep basin have been inferred from a limited number of hydrocasts, so we know neither the temporal nor spatial variability. The behavior of the source waters for deep circulation, the inflow of the DPW through Kamchatka Pass, is not known.
The processes that result in the exchange of slope and shelf waters have not yet been determined. Hence, we do not know the mechanisms that provide nutrients to the euphotic zone and are responsible for the region of prolonged biological production known as the "Green Belt" (Springer et al. 1996). While the processes are unknown, the results of their interactions are evident. The continental shelf of the Bering Sea exhibits extremely high productivity, and this richness applies throughout the food chain. Not only are there vast quantities of commercially valuable species, but the eastern shelf is the summer feeding ground for numerous marine bird and marine mammal populations of the North Pacific Ocean. The eastern Bering Sea provides an ideal location to examine exchange mechanisms between slope water of an eastern boundary current and a continental shelf. Because the coast and its inherent topographic and coastal convergence processes are far removed from the slope, the processes involved in shelf/slope exchange should provide a clear signal. The continental shelf of the western Bering Sea is bounded by a typical western boundary current, so that contrasts of processes between the eastern and western shelves should be fruitful.
Future studies that focus on how the extant physical phenomena affect marine populations offer the best opportunity to enhance our understanding of ecosystem dynamics. This, in turn, could lead to management strategies aimed at sustainable production to ensure a rich ecosystem for our future generations. The observational database for the Bering Sea is not adequate, in both spatial and temporal coverage, to answer most of the questions noted above. In addition to further observations, modeling efforts need to be improved. A primitive equation basin-shelf model coupled to both outflow through Bering Strait and exchange in the North Pacific Ocean is a likely starting place. Once the model provides accurate simulations of the physical features, then biophysical processes and rates can be incorporated. Some of the questions that must be addressed to understand the ecosystem are best investigated by modeling efforts.
We thank the numerous scientists who planned, conducted, and published their research. We also thank all the technical staff who assisted with the data acquisition, preparation, and analysis. This contribution was funded by the Coastal Ocean Programs Bering Sea FOCI and by the Fisheries Oceanography Coordinated Investigations of NOAA (#BS302), and is Pacific Marine Environmental Laboratory's contribution #1878.
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