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

Abstract. In the high latitude Arctic, wintertime sea ice and snow insulate the relatively warmer ocean from the colder atmosphere. As the climate warms, wintertime Arctic surface heat fluxes will be dominated by the insulating effect of snow and sea-ice covering the ocean until the sea ice thins enough or sea ice concentrations decrease enough such that direct ocean-atmosphere heat fluxes become more important. Simulated wintertime conductive heat fluxes in the ice-covered Arctic Ocean increase ~7–11 W m−2 by mid-21st century and are due to both thinning sea ice and snow on sea ice. Surface heat flux estimates calculated using grid-cell mean values of sea ice thicknesses underestimate mean heat fluxes by ~16–35 % and overestimate changes in conductive heat fluxes by up to ~36 % in the wintertime Arctic basin even while sea ice concentrations remain above 90 %.