The issue focused on sea ice extent at three polar stations (West Antarctica, Greenland and Alaska). Sea ice extent reached record lows over most of the Arctic Ocean during summer 2010 and reduced rapidly during winter 2010 and 2011. Ocean circulation patterns associated with global warming played a role in driving sea ice retreat and thereby enhancing warming in the Arctic Ocean. Climate scientists observed several variations in sea ice extent during summer 2010 and winter 2011 (magenta circles), showing both spatiotemporal variability and trends that cannot be attributed to natural variability