OCEAN CIRCULATION IN THE BERING SEA MARGINAL ICE-EDGE ZONE FROM ACOUSTIC DOPPLER-CURRENT-PROFILER OBSERVATIONS

A quantitative description of vertical plane circulation in the Bering Sea marginal ice zone (MIZ) is presented. The analysis consists of oc ean current observations supported by an analytic model with biologica l and nutrient observations as corroborative support for the circulati on. Horizontal currents were acquired with an Acoustic Doppler Current Profiler (ADCP) along five cross-sections through the MIZ in April-Ma y 1987. Tidal current calculations, using a coincident current meter m ooring for calibration, were subtracted from the ADCP data to extract the residual horizontal currents. Vertical currents were then calculat ed through continuity in which along-ice variability was assumed to be negligible. The results reveal circulation cells in each of two front s associated with the MIZ. The most energetic upwelling (similar to 2- 3 m day(-1)) occurs primarily within the two fronts, while the most en ergetic downwelling (similar to 1 m day(-1)) occurs in the stratified water between the two fronts. In support of the observed and modeled c irculation, maxima in both the mean chlorophyll as well as the mean in tegrated chlorophyll/nitrogen ratio from these same five cross-section s coincide with upwelling while a relative minimum in both chlorophyll and the chlorophyll/nitrogen ratio coincides with downwelling. The po sitive correlation between the biological and chemical observations an d the mean vertical flow corroborate the existence of persistent verti cal circulation cells associated with the Bering Sea MIZ frontal struc ture as well as suggesting that the technique of using ADCP measured v elocities in the calculation of vertical Bow is valid.