Mapping of Antarctic sea ice in the depletion phase: an indicator of climatic change?

摘要

The mapping and monitoring of the sea ice variability in the polar regions is of prime importance for global climate modelling. Apart from sea ice, spatial snow cover variability and depth estimates are needed for accurate assessment of many climate parameters required in the ice-ocean models. Mapping and analysing the spatial and temporal variability of Antarctic sea ice and snow cover are therefore highly important for polar ice-pack studies in the global climate cycle. The present study has been carried out mainly for sea ice mapping surrounding Antarctica using Special Sensor Microwave Imager (SSM/I) passive microwave data during its depletion phase (November 2001 to January 2002). Sea ice concentrations and snow depths over the Antarctic sea ice have been calculated and their temporal variation patterns studied. The overall ex-tents under all ice concentration categories during different months over the study period have decreased in the order of 1 to 3 million km 2 in comparison to the sea ice concentration categories during 1978–87 period. The thermal conductivity of snow is about an order of magnitude less than the sea ice. Hence the presence of small amount of snow on sea ice can greatly affect the heat flux between the sea surface and atmosphere. Depletion in snow depths over sea ice (from 1988–94 to 2001–02) could be observed particularly in December, though not much change has been observed in November and January. These changes (shrinking ice covers/depletion in sea ice concentration) can be attributed to some locally changing weather patterns in the Antarctic continent as well as due to regional phenomenon like global warming.