DETERMINATION OF SURFACE TURBULENT FLUXES OVER LEADS IN ARCTIC SEA-ICE

We present a new model to compute turbulent surface heat and momentum fluxes over leads in the Arctic sea ice. The momentum roughness length uses a sea state parameterization which is fully consistent with the surface turbulent flux parameterization. The flux parameterization acc ounts for the fetch limitation of the airflow over a lead. The surface roughness length for heat is determined from an application of surfac e renewal theory to the air-sea interface. The modeled fluxes are comp ared with in situ observations of lead fluxes. We also compare our mod el results with a bulk flux algorithm which has been commonly used to evaluate surface heat fluxes from leads. We perform sensitivity studie s to examine the role of the surface renewal timescale, the importance of the cool skin, and impact of wave age dependence on the momentum r oughness length. We have computed integral heat fluxes as a function o f lead width/fetch for various atmospheric states to determine the mag nitude of heat flux in a mesoscale model grid in which a lead is prese nt.