The Evolution of Water Column Hydrography Beneath Landfast Sea Ice Near Prudhoe Bay, Alaska During the Spring Freshet

Stephen R Okkonen, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, Fairbanks, United States and Samuel R Laney, Woods Hole Oceanographic Institution, Woods Hole, MA, United States
Abstract:
The spring freshet in northern Alaska largely discharges beneath a canopy of landfast sea ice along the Beaufort coast. This phenomenon was monitored during late spring-early summer 2018 and 2019 by an array of moored and through-ice sensors deployed in Stefansson Sound near Prudhoe Bay, Alaska. Acoustic Doppler current profiler (ADCP) measurements of acoustic backscatter and currents complemented by measurements of temperature and salinity show that prior to the freshet the water column is weakly-sheared and unstratified. With the onset of the freshet, heat carried by the freshet melts the overlying sea ice from below. The water column subsequently transitions to a strongly-sheared, two-layer system with interface depth increasing monotonically to a depth of ~4 m until the overlying ice cover breaks up. Open water allows winds to mix the water column and break down stratification.