A review of recent changes in Southern Ocean sea ice, their drivers and forcings

• Antarctic sea ice has expanded over the last 37 years.
• The change in total coverage masks intense local increases and decreases.
• The primary driver is thought to be regional changes in the atmospheric circulation.
• Ocean feedbacks are also essential; the relative roles of atmosphere and ocean drivers is not well known.
• There is high uncertainty on the anthropogenic contribution to these trends.

Over the past 37 years, satellite records show an increase in Antarctic sea ice cover that is most pronounced in the period of sea ice growth. This trend is dominated by increased sea ice coverage in the western Ross Sea, and is mitigated by a strong decrease in the Bellingshausen and Amundsen seas. The trends in sea ice areal coverage are accompanied by related trends in yearly duration. These changes have implications for ecosystems, as well as global and regional climate. In this review, we summarise the research to date on observing these trends, identifying their drivers, and assessing the role of anthropogenic climate change. Whilst the atmosphere is thought to be the primary driver, the ocean is also essential in explaining the seasonality of the trend patterns. Detecting an anthropogenic signal in Antarctic sea ice is particularly challenging for a number of reasons: the expected response is small compared to the very high natural variability of the system; the observational record is relatively short; and the ability of global coupled climate models to faithfully represent the complex Antarctic climate system is in doubt.