Antarctic sea ice: variability and trends from 1978 to 2006

Abstract

Sea ice plays an important role on Earth's climate. Besides its high albedo, sea ice isolates ocean from atmosphere and also plays an important role in deep water formation through brine rejection. Earth's recent climate changes may be affecting significantly these processes. In this work, we analyzed the variability of sea ice concentration around the Antarctic continent using SMMR and SSMI data for the 1978-2006 period. We investigated the annual trends by linear regression at 95% confidence level. Then, we used the Empirical Orthogonal Functions (EOF) technique to decompose the sea ice cover signal into independent modes of variability. We found a negative annual linear trend around the tip of the west Antarctic Peninsula and in the Bellingshausen/Amundsen Seas over the 32 years period. In the vicinities of the Ross Sea, a positive trend was observed. These results confirm recent trends observed by other studies in Antarctica. Seasonal variability dominated the sea ice over the period as expected. The seasonal-removed sea ice variability has shown the dominance of a 3-4 year period signal. We conclude this to be due to El Niño Southern Oscillation (ENSO) and Southern Annular Mode (SAM) forcing, and intrusion of relatively warmer water into the Bellingshausen/Amundsen Seas. Sea ice cover around Antarctica is a complex matter but as the time series become longer, the non-linearity of many physical processes can be accessed in the future.