Circulation in the Landfast Ice Zone of the Alaskan Beaufort Sea

We present 3 years of ADCP and temperature, salinity, and transmissivity data collected year-round on the inner shelf (10 m depth) of the Alaskan Beaufort Sea. The results capture the variable circulation dynamics and water properties induced by seasonal changes in landfast ice and the pulse-like nature of arctic river discharges. An immobile lid of landfast ice, extending from the coast to the 25 m isobath, covers the inner shelf from October - June. When ice is present, currents are along-shore polarized, weak (<5 cm/s; but sometimes >10 cm/s) and uncorrelated with regional winds. Time-varying along-shore pressure gradients of O(10^-7) of unknown origin are implied. During the spring river freshet, a highly sheared and strongly stratified under-ice plume spreads offshore at O(10 cm/s) and is accompanied by rapid settling of terrestrial sediments. After ice breakup, swift (>25 cm/s) along-shore flows dominate that are correlated with the winds, and accompanied by implied along-shore pressure gradients of O(10^-6). These currents re-suspend and disperse the sediment load that settled out during the spring freshet. In contrast to earlier results, the mean flow here is negligible, implying a negligible mean along-shore pressure gradient. Our results suggest little cross-shore exchange between the landfast ice zone and the outer shelf in winter and raise questions regarding the role of landfast ice on frictional control of the under-ice circulation and the spreading of under-ice river plumes.