Simulated Changes in Arctic Cold Season Surface Heat Fluxes and the Relative Influences of Sea Ice Concentration, Sea Ice Thickness and the Sea Ice Thickness Distribution

Abstract:

Arctic near-surface warming is strongly influenced by both sea ice concentration (SIC) and sea ice thickness (SIT). During the polar night, when albedos play no direct role in surface heat budgets and ice concentration is high, sea ice influences surface warming through insulation of the relatively warm ocean from the overlying cold atmosphere. Over the observational record, central Arctic sea ice has thinned dramatically, even though winter concentrations remain high. Winter warming during this period has been influenced by sea ice thickness changes. As the Arctic continues to warm, however, the relative roles of SIC and SIT to wintertime surface warming will change. Furthermore, the non-linear relationship between sea ice thickness and the conduction of heat through the ice suggests that the impacts of SIT on surface heat flux will also depend on the heterogeneity of the SIT fields

We use the Community Earth System Model Large Ensemble to explore both the relative roles of SIC and SIT changes, and the influence of heterogeneity in SIT fields to central Arctic wintertime surface heat fluxes under the RCP8.5 scenario. We assess how these relative roles differ over the cold season and vary throughout the 21^st century. Using sub-gridscale sea ice thickness distribution changes simulated by the model, we explore the influence of simplified ice thickness distributions on surface heat fluxes. Comparisons between different sea ice thickness categories to grid-cell averaged SIT and surface heat fluxes can help guide both modeling studies of future changes, as well as observational sea ice thickness campaigns.