Introducing katabatic winds in global ERA40 fields to simulate their impacts on the Southern Ocean and sea-ice

摘要: A medium resolution (10-20 km around Antarctica) global ocean/sea-ice model is used to evaluate the impact of katabatic winds on sea-ice and hydrography. correction developed compensate for drastic underestimation these in ERA40 reanalysis. This derives from a comparison over 1980-1989 between wind stress those downscaled by MAR regional atmospheric model. The representation continental orography surrounding ocean, like Transantarctic Mountains, specific parameterisation roughness length planetary boundary layer yield major improvement along coast Antarctica. Wind directions at first ocean point are remarkably similar MAR, but amplitudes much greater. From this comparison, scale factor constant time (i.e. no seasonal variation) spatially varying (decreasing off-shore distance about 150 km) created meridional zonal components adapted vector. thus consists local amplification amplitude 6-hourly vector points near coast. investigated 40-year long twin simulations polynyas increased 2, sensible latent air-sea heat exchanges 28% 18%, respectively. Sea-ice thickness ice-fraction Antarctica show marked decrease. amplified also increase extent coastal 24% total polynya area augmented 60,000 km3 Antarctica), winter production greater 42%. Outside polynyas, reduction Southern Ocean pack. Impacts circulation marked. Katabatic strengthens overturning with more intense transformation Antarctic Surface Waters into colder denser shelf waters (in all Antarctica, reaches 4.7 Sv annual mean, an 1.8 Sv, peaks 6 winter). modification water properties surface yields cycle Coastal Current.