Antarctic sea ice passive microwave signatures during summer and autumn

The microwave signatures of Antarctic sea ice during the summer and autumn of 1992 are examined using SSM/I data in conjunction with ERS-1 SAR data and observations from an ice station in the Western Weddell Sea region. The period from February through April is observed to be critical in terms of monitoring sea ice cover with passive microwave sensors because of surface effects (e.g., melt, slush and flooding) that may cause large fluctuations in the signature of sea ice during the period. The concentrations calculated using reference brightness temperatures normally used for winter data are considerably lower than those observed in the field and those derived from the SAR data. Reference temperatures more appropriate for the summer ice data were inferred and provided more compatible ice concentrations. In late summer and autumn, freezing conditions begin to dominate and the brightness temperatures of sea ice, still different from those of winter, reflect those primarily of refrozen slush over thick ice, young ice, and new ice