Monday, 10 January 2005: 5:00 PM
Parameterizing the turbulent surface fluxes over summer sea ice
During summer, the surface of the Arctic Ocean is no longer simply snow-covered sea ice, as in winter. For example, during the 1997–1998 Surface Heat Budget of the Arctic Ocean (SHEBA) experiment, the surface evolved from compact, snow-covered sea ice in mid-May 1998 to a surface with 62% bare ice, 19% melt ponds, and 19% leads in early August. By early October, the surface was again compact, snow-covered ice. Our eddy-correlation measurements in the main SHEBA camp and at four remote sites capture the evolution of the drag coefficient and the transfer coefficient for sensible heat as summer progresses. From these measurements, we develop a parameterization for the drag coefficient over summer sea ice that depends simply on the water fraction. Because the physics that controls momentum transfer over surfaces composed of ice and water depends on the vertical ice edges associated with the water, we extend our parameterization to marginal ice zones, where it also yields reasonable predictions. Andreas’s 1987 theoretical model for sensible heat transfer over compact, snow-covered sea ice also seems appropriate over summer sea ice if we use the areally averaged surface temperature in the parameterization. That original model required only a single surface temperature that is appropriate for winter sea ice; whereas in the summer, the ice, the ponds, and the leads all, generally, have different surface temperatures.