Atmospheric boundary‐layer modification, drag coefficient, and surface heat flux in the Antarctic marginal ice zone

Abstract

During a traverse of the Antarctic marginal ice zone (MIZ) near the Greenwich Meridian in October 1981, we launched a series of radiosondes along a 150‐km track starting at the ice edge. Since the wind was from the north, off the ocean, these radiosonde profiles showed profound modification of the atmospheric boundary layer (ABL) as the increasing surface roughness decelerated the flow. The primary manifestation of this modification was a lifting of the inversion layer with increasing distance from the ice edge by the induced vertical velocity. But there was also a cooling of the stably stratified mixed layer below the inversion and a consequent flux of sensible heat to the surface that averaged over 200 W/m 2 . The magnitude of this flux suggests that atmospheric heat transport plays a significant role in the destruction of ice in the Antarctic MIZ. Using the rising of the inversion and ABL similarity theory, we estimated the change in the neutral stability drag coefficient, C D , across the MIZ. C D increased from its open ocean value, 1.2×10 −3 , at the ice edge to 4.0×10 −3 at 80–90% ice concentration. We present an equation for this dependence of drag on ice concentration that should be useful for modeling the surface stress in marginal ice zones.