The Arctic snow and air temperature budget over sea ice during winter

Abstract

Arctic cooling through the fall-winter transition is calculated from a coupled atmosphere-sea ice thermal model and compared to temperature soundings and surface measurements. A typical winter, clear-sky vertical temperature structure of the polar air mass is composed of a surface-based temperature inversion or an inversion above a very shallow (30-180 m) mechanically mixed boundary layer with temperatures -30° to -35°C, a broad temperature maximum layer of -20° to -25°C between 0.5 and 2 km, and a negative lapse rate aloft. A 90-day simulation shows that heat flux through the ice is insufficient to maintain a local thermal equilibrium. Northward temperature advection by transient storms is required to balance outward longwave radiation to space. We propose that the strength of boundary layer stability, and thus the degree of air-ice momentum coupling, is driven by the magnitude of the radiation deficit (downward-outward longwave) at the surface and the potential temperature of the temperature maximum layer. It may be possible to obtain a radiation deficit field via satellite sensors. -from Authors