Gaining (and losing) Antarctic sea ice: variability, trends and mechanisms

Every year Antarctic sea ice undergoes a six-fold change in ice-covered area; it is one of the largest seasonal signals on earth. It is however highly variable and frequently exposed to strong storms, high winds and waves. These factors affect Antarctic sea ice growth and melt processes, thickness evolution and drift and impart high regional and seasonal variability. Over the past four decades there has been a modest increase in spatially averaged Antarctic sea ice extent, but this hides very large but opposing regional sea ice trends. In the highest trending regions, rates of change are comparable to those observed in the Arctic, but elsewhere around Antarctica, sea ice trends lie within the range of natural variability. Local differences in air-sea-ice interactions and sensitivity to large-scale climate variability create a complex picture in terms of attribution. Historical sea ice observations lend perspective, suggesting different behavior in the recent past.