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Abstract:
The meridional wind, which can modulate the sea-ice extent with its stress, has been changing over the Antarctic sea-ice region and has partially contributed to the variability of the Antarctic sea-ice extent. We use observations and an eddy-resolving numerical model to investigate how meridional wind variability affects sea-ice distribution, as well as ocean states and circulation in the Southern Ocean. The results show that southerly wind anomalies in austral winter lead to an increased sea-ice extent with equatorward sea ice drift, resulting in more ice production and buoyancy loss in the coastal region and freshening near the Antarctic Circumpolar Current. In contrast, southerly wind anomalies in austral summer reduce the sea-ice extent owing to a positive temperature anomaly near the sea-ice edge. This positive anomaly results from the enhanced meridional overturning circulation under the southerly wind anomalies, which brings relatively warm water-masses toward the summertime sea-ice edge. The water-mass transformation analysis suggests that the enhancement of the meridional overturning circulation stems from the increased deep water formation caused by brine rejection and heat loss at the polynyas. The sea-ice extent, ocean states, and meridional overturning circulation behave the opposite way under northerly wind anomalies. These results suggest that meridional wind changes can modify not only the sea-ice distribution but also the ocean's meridional overturning circulation through the buoyancy fluxes at the polynyas.
