In recent years, satellite data have indicated an even more dramatic reduction in regional ice cover.

September Average Extents, 2002-2017: Calculated by Walt Meier and Julienne Stroeve, National Snow and Ice Data Center. All values in table estimated based on the NSIDC Sea Ice Index. Note that these figures show September average extents rather than minimum extents.

The Arctic sea ice September minimum extent reached a new record low in 2012 of 3.41 million square kilometers, 44 percent below the 1981-2010 average, and 16 percent below the previous record in 2007. Over the last 13 years, a new record was set four times (2002, 2005, 2007, and 2012) and several other years saw near-record lows, particularly 2008 and 2011. On September 10, 2016, Arctic sea ice extent dipped to 4.14 million square kilometers, reaching a statistical tie with the 2007 minimum for second-lowest in the satellite record. In 2017, extents were higher but still below the 1981-2010 average. The 10 lowest September ice extents over the satellite record have all occurred since 2007.

The spring and summer weather conditions play an important role in the minimum extent and the spatial distribution of ice at the end of summer, and help determine if a particular year will be a record low. For example, in 2007, persistent winds through the summer helped to contract the ice to a new minimum record. In 2012, conditions were less favorable to ice retreat through the summer, although a strong cyclone in early August helped break up the ice and enhance melt. Regardless of weather patterns, the Arctic September ice extent shows a consistent downward trend in extent and thickness over the satellite record.

Arctic and Antarctic extents, 1979-2017: In early 2017, the Arctic sea ice maximum extent was the lowest on record. At the same time, the Antarctic minimum extent was the lowest on record, though the Antarctic had not shown a clear declining trend over time. Image adapted by Climate.gov from NSIDC's Charctic.

Arctic Sea Ice Thickness Comparisons: These graphs from Kwok and Rothrock 2009 compare sea ice thickness observations from submarine records and ICESat observations over time. The bar chart (left) compares sea ice thickness for six Arctic regions. The time series (right) shows submarine sonar measurements compiled in studies published 2008 and 2009 (designated as RA), and ICESat observations. Error bars on the February-March measurements appear as vertical blue bars.

Actual temperature increase in the Arctic: