Investigating Variability of Antarctic Sea Ice on Subseasonal-to-Seasonal Time Scales

Antarctic sea ice has been studied for several decades and is an important part of the climatology of the region. Sea ice forms via the complex interactions of wind, temperature, waves and salinity, as well as decays in response to these components. The Antarctic can be divided into five sectors: the Weddell Sea, the Indian Ocean, the western Pacific Ocean, the Ross Sea, and the Bellingshausen/Amundsen seas, with each sector’s sea ice responding slightly differently to the parameters mentioned above. Trends in sea ice concentration, extent and area in each sector have been examined, with sea ice concentration being derived from observations by satellite passive microwave radiometers. Sea ice extent and area are calculated using a particular grid point’s sea ice concentration, with a 15% threshold being used to denote complete ice coverage. Given that estimation, each grid point can be analyzed to determine if it is ice-free or ice-covered. Such trends in ice extent are particularly important to shipping, marine life, cloud coverage and more.

In this study, daily sea ice extent (SIE) and area (SIA) were calculated from daily sea ice concentration available from the NOAA-Climate Data Record (CDR). SIE and SIA were composited to determine relationships of ice change over particular months and years. The gridded product is available over the entire Southern Hemisphere at a spatial resolution of 25 km. This work extends previous studies of SIE and SIA to include the most current observation. Previous work showed an increase in SIE and SIA over the entire Southern Hemisphere, Weddell Sea, the western Pacific Ocean, the Ross Sea, and Indian Ocean sectors with a negative trend in Bellingshausen/Amundsen seas, particularly between 1998-2006. Preliminary results show these upward trends may have reversed in certain sectors as well as in the Southern Hemisphere at large. Implications of these results will be explored in more detail.