A coupled sea ice - Large Eddy Simulation (LES) model is used to examine the role of leads in controlling the salinity and heat content of the upper ocean under sea ice. Experiments are performed by varying the lead width, sea ice velocity, and surface forcing. Eddy fluxes of salinity in the model show good comparison with observed fluxes from the LEADEX experiment. In particular, salinity fluxes on the downwind side of the lead are an order of magnitude larger than fluxes under the sea ice. The model demonstrates that with ice motion, turbulence under the sea ice is dominated by shear production resulting from dynamic roughness of the ice bottom surface. However, as ice motion falls below ~6 cm/s, buoyancy forcing has an increasing influence on the turbulent structure, promoting the generation of coherent structures such as longitudinal rolls. Near the lead, turbulence is dominated by convection from salinity flux and momentum input from wind stress over the open water of the lead. Overall, the results show that small leads (~100-200 m) can be treated as part of the aggregated flux when sea ice motion is greater than ~3 cm/s. Below this velocity, the boundary layer structure near the lead takes on different properties in comparison to the surrounding water (colder and more saline). In addition, upward entrainment mixing of halocline water beneath the lead is slightly enhanced, although it is still much smaller than the surface salinity flux (by about an order of magnitude) and is limited to the upper ~5 m of the halocline