Turbulent heat and momentum transfer in the oceanic boundary layer under melting pack ice

Abstract

A theory for momentum flux in the planetary boundary layer (PBL) stabilized by continuous surface buoyancy is extended to include turbulent flux of an arbitrary scalar contaminant and then used to estimate how wind‐driven sea ice melts as it encounters temperatures in the oceanic boundary layer that are above the melting point. Given wind stress and temperature difference Δθ across the oceanic PBL, the theory predicts melt rate and ice drift velocity. Results indicate that the effect of buoyancy on PBL turbulence is significant even with small values of Δθ(<0.5 K). Curves of melt rate and ice speed as functions of u*, the interfacial friction velocity, show that melting is strongly dependent on stress at the interface and that the effective drag on the ice undersurface is significantly reduced at oceanic temperatures commonly observed in the marginal ice zone. The latter suggests that divergence will occur at the ice margin when off‐ice winds advect the pack over water above the melting temperature. The structure of mean currents beneath the ice is also investigated; results indicate that advection will play an important, if not dominant, role in determining water column properties near an ice edge front.