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 ocean current observations supported by an analytic; model with biological and nutrient observations as corroborative support for the circulation. Horizontal currents were acquired with an Acoustic Doppler Current Profiler (ADCP) along five cross-sections through the MIZ in April-May 1987. Tidal current calculations, using a coincident current meter mooring for calibration, were subtracted from the ADCP data to extract the residual horizontal currents. Vertical currents were then calculated through continuity in which along-ice variability was assumed to be negligible. The results reveal circulation cells in each of two fronts associated with the MIZ. The most energetic upwelling (∼2–3 m day-) occurs primarily within the two fronts, while the most energetic downwelling (∼1 m dayʹ) occurs in the stratified water between the two fronts. In support of the observed and modeled circulation, maxima in both the mean chlorophyll as well as the mean integrated chlorophyll/nitrogen ratio from these same five cross-sections coincide with upwelling while a relative minimum in both chlorophyll and the chlorophyll/nitrogen ratio coincides with downwelling. The positive correlation between the biological and chemical observations and the mean vertical flow corroborate the existence of persistent vertical circulation cells associated with the Bering Sea MIZ frontal structure as well as suggesting that the technique of using ADCP measured velocities in the calculation of vertical flow is valid.