Sensitivity of Air-Sea Heat Exchange in Cold-Air Outbreaks to Model Resolution and Sea-Ice Distribution

Modeling air-sea interactions during cold air outbreaks poses a major challenge because of the vast range of scales and physical processes involved. Using the Polar WRF model, we investigate the sensitivity of downstream air mass properties to (a) model resolution, (b) the sharpness of the marginal-ice zone (MIZ), and (c) the geometry of the sea ice edge. The resolved sharpness of the MIZ strongly affects peak heat fluxes and the atmospheric water cycle. For sharper MIZs, roll convection is initiated closer to the sea ice edge, increasing both evaporation and precipitation. This yields an increased heat transfer into the atmosphere while the net effect on the atmospheric moisture budget is small. Overall, higher atmospheric resolution increases both the peak and net heat extracted from the ocean. The geometry of the sea ice edge can induce convergence or divergence zones that affect the air-sea exchange. Plain Language Summary In the Arctic, sea-ice insulates a relatively warm ocean from a rather cold atmosphere. From time to time, very cold air masses spill out from the sea ice over the open ocean. When this happens, large amounts of heat and moisture are released from the ocean into the atmosphere, heating and moistening the air above while cooling the ocean. In this study, we investigate how the modeled heat and moisture exchange depends on the resolution of the atmospheric model and on properties of the marginal ice zone between the pack ice and the open ocean. The higher the resolution of the atmospheric model and the sharper the transition from the pack ice to the open ocean, the more heat and moisture is released from the ocean into the atmosphere. This dependence of the heating on model resolution is particularly pronounced close to the sea-ice edge.