The effect of alternative real‐time wind forcing on Southern Ocean sea ice simulations

Abstract

Southern Ocean (SO) sea ice simulations are particularly sensitive to wind forcing. Two real‐time wind data sets covering the same period are employed to force SO sea ice in a sea ice–ocean general circulation model. Both data sets are analysis products, featuring the same temporal resolution but differing in their horizontal resolution and their source. Even in simulations where the upper ocean temperature is constrained by satellite‐derived sea ice concentration, the sea ice simulations and associated surface buoyancy fluxes reveal pronounced differences along the Antarctic coastline. While the discrepancies cannot unambiguously be related to the different resolution of the wind forcing, their concentration along the coastline is indicative of being related to the representation of orography, such as coastal steep slopes and mountain ranges, including their ruggedness. Along the coast of the Weddell Sea, the net ice production rate increases by about a factor of 3 with the higher‐resolution winds. On the other hand, along east Antarctica, the lower‐resolution winds result in higher ice production, due to a generally stronger (overestimated) offshore component, presumably related to the smoother orography extending seaward beyond the coastline. This regionally opposite behavior leads to a relatively weak difference in total dense water formation around Antarctica and thus global deep ocean properties and circulation. Overall, the results indicate that long‐term climate model projections are likely to be highly sensitive to model resolution in the Antarctic coastal zone.