Oceanography of the eastern Bering Sea ice‐edge zone in spring1

Abstract

The ice‐edge region of the southeast Bering Sea was studied in terms of the hydrographic regime, phytoplankton biomass, and primary productivity during the springs of 1975 through 1977. The results showed that a phytoplankton bloom occurs at the ice edge just as the spring ice‐decay period begins, and that this accounts for a significant proportion of the annual carbon input over the shallow shelf. The bloom is intensified in time and space by the influence of the ice edge on the physical structure of the water column. Specifically, melting ice seems to increase the stability of the water column, near and under the ice, by lowering the salinity. Frontal structure in salinity and temperature are apparent at the ice edge and are attributed to the melting ice but also, at times, to wind‐driven Ekman‐type upwelling.These data are also related to recent short term (ca. months‐year) climatic fluctuations that seem to control the seasonal position of the ice‐edge zone relative to the shelf break. In “cold” years, the ice edge comes southward to the shelf break and overlies the more nutrient‐rich Alaska Stream/Bering Sea source water. In “warm” years, the ice‐edge zone does not reach this nutrient‐rich water. This may be important to the biology of the ice‐edge ecosystem.