Impacts of Short-Term Wind Events on Chukchi Hydrography and Sea Ice Retreat

KoFan Lu, UAF, School of Fisheries and Ocean Sciences, Fairbanks, AK, United States, Seth L Danielson, UAF, College of Fisheries and Ocean Sciences, Fairbanks, AK, United States and Thomas Weingartner, University of Alaska Fairbanks, College of Fisheries and Ocean Sciences, Fairbanks, AK, United States
Abstract:
We seek a better understanding of the summer ice retreat over the Chukchi shelf by investigating mechanisms through which wind forcing mediates changes in sea ice cover, water column hydrography, and their inter-related evolution in time, in the presence of a warm background inflow. The problem is addressed with an idealized depiction of the Chukchi Sea’s Central Channel within the Regional Ocean Modeling System (ROMS) framework, forced with inflow from the south, surface heat fluxes, and surface wind stresses of varied magnitudes and directions. Due to strong atmosphere-ice coupling, direct wind-forced advection of the ice edge emerges as the over-riding factor that triggers numerous consequences. These include Ekman surface convergences and divergences, which decrease and increase vertical transport, respectively, and corresponding alterations of the sea surface height. Somewhat surprisingly, we find no significant wind control of the cross-frontal eddy transport, due to counter balances between the frontal density gradient and the pycnocline depth. We propose a conceptual model for understanding the net impact of the wind influence on the Chukchi shelf ice retreat and hydrographic structure. Advection of ice away from the inflow reduces the ice melt rate and increases the salinity of the meltwater plume. Advection of ice toward the inflow increases the ice melt rate and decreases the meltwater plume salinity. The identified mechanisms represent steps toward a more complete understanding of the summer conditions in the Chukchi Sea and will help future investigations of seasonally ice-covered shelf ecosystems.