Influence of Sea Ice Thickness on the Atmosphere in the Winter Arctic Region in an Atmospheric General Circulation Model

Abstract

The influence of sea ice thickness on the winter Arctic atmosphere has been investigated using an atmospheric general circulation model, focusing on heat fluxes at the sea ice surface. Due to heat conduction from the sea ice bottom, the sea ice surface temperature increases when the sea ice becomes thin. However, the heat balance among net longwave cooling, sensible and latent heat fluxes, and heat conduction changes with sea ice thickness. When the sea ice is thick, longwave cooling is balanced with the heating of heat conduction and downward sensible heat flux. When the sea ice is sufficiently thin, cooling by sensible and latent heat fluxes plays a large role in heat balance at the sea ice surface, canceling the increase of downward longwave heating associated with cloud change. It is suggested that thinner sea ice leads to warming of a large part of the troposphere in the Arctic region, causing a weakening of upper westerly wind in the sub-arctic region. The magnitude of such a wind response to possible sea ice thickness variability can be 10-20% of interannual variability.