Influences of changing sea ice and snow thicknesses on simulated Arctic winter heat fluxes

While the climate warms, wintertime Arctic surface heat fluxes remain dominated by the insulating effects of snow and sea ice covering the ocean until the sea ice thins enough or sea ice concentrations decrease enough to allow for direct ocean-atmosphere heat fluxes. The Community Earth System Model version 1 Large Ensemble (CESM1-LE) simulates increases in wintertime conductive heat fluxes in the ice-covered Arctic Ocean by similar to 7-11 W m(-2) by the mid-21st century, thereby driving an increased warming of the atmosphere.

These increased fluxes are due to both thinning sea ice and decreasing snow on sea ice. The simulations analyzed here use a sub-grid-scale ice thickness distribution. Surface heat flux estimates calculated using grid-cell mean values of sea ice thicknesses underestimate mean heat fluxes by similar to 16 %-35 % and overestimate changes in conductive heat fluxes by up to similar to 36 % in the wintertime Arctic basin even when sea ice concentrations remain above 95 %.