Sea Ice Response to Wind Forcing from AMIP Models

Abstract

The Arctic surface circulation simulated by atmospheric general circulation models is assessed in the context of driving sea ice motion. A sea ice model is forced by geostrophic winds from eight models participating in the first Atmospheric Model Intercomparison Project (AMIP1), and the results are compared to simulations with the sea ice model forced by observed winds. The mean sea level pressure in the AMIP models is generally too high over the Arctic Ocean, except in the Beaufort and Chukchi Seas, where it is too low. This pattern creates anomalous winds that tend to transport too much ice away from the coast of Greenland and the Canadian Archipalego, and into the East Siberian Sea, producing a pattern of ice thickness in the Arctic that is rotated by roughly 180° relative to what is expected based on observations. AMIP winds also drive too little ice transport through Fram Strait and too much transport east of Svalbard by way of the Barents Sea. These errors in ice thickness and transport influence ice growth and melt rates and hence the freshwater flux into the ocean. Sensitivity experiments that test the model response to the wind composition show the ice thickness patterns depend primarily on the climatological mean annual cycle of the geostrophic winds. Daily wind variability is necessary to create sufficient ice deformation and open water, but the sea ice behavior is rather insensitive to the details of the daily variations.