Large-eddy simulation of turbulent processes in summertime leads

 

 

Simulations of three-dimensional circulations within leads are performed to quantify the effects of leads on ice melting rates. We consider an idealized square lead, roughly 18 m on each side, located in a periodic 45 m x 45 m domain. Ice thickness is set to 1.5 m and a fresh layer at the freezing temperature is initialized over the top 0.5 m of the lead. The remaining water mass is initialized using a temperature, salinity profile appropriate for early summer. Ice motion is set to 0.05 m s-1, with the lead surface forced by penetrative solar radiation and a surface wind stress of 0.05 Nt m-2. Results from the simulation show a complex circulation pattern within the lead that is dominated by the downwind transport of water. On the upwind side of the lead, cooler water is upwelled, resulting in lower ice melting rates. However, maximum melting rates are indicated along the southern edge of the lead because of a circulation pattern that causes greater southward transport. Simulations show that melting heat fluxes within the lead average about 60 W m-2, whereas the average underice melting flux is about 14 W m-2. Within the lead, melting heat fluxes vary significantly; above the fresh water cap values range from -400 to -200 W m-2, under the cap values are more similar to the under ice fluxes. Overall, trapping of heat by the fresh water layer in the lead causes much more intense melting relative to the under ice region. Our results are compared with observations taken within leads during the SHEBA field experiment.