page_title: Arctic sea ice decline
hierarchical_section_title: Arctic sea ice decline
caption_attribution_description: English: Arctic sea ice extent anomaly.
context_page_description: In recent decades, sea ice in the Arctic Ocean has been melting faster than it re-freezes in winter. The Intergovernmental Panel on Climate Change Fourth Assessment Report states that greenhouse gas forcing is predominantly responsible for the decline in Arctic sea ice extent. A 2007 study found the decline to be "faster than forecasted" by model simulations.
  A 2011 study suggested that this could be reconciled by internal variability enhancing the greenhouse gas-forced sea ice decline over the last few decades. A 2012 study with a newer set of simulations also projected rates of retreat which were somewhat less than that actually observed.
  The IPCC Fifth Assessment Report concluded, with high confidence, that sea ice will continue to decrease in extent, and that there is robust evidence for the downward trend in Arctic summer sea ice extent since 1979. It has been established that the region is at its warmest for at least 4,000 years and the Arctic-wide melt season has lengthened at a rate of 5 days per decade, dominated by a later autumn freeze-up. Sea ice changes have been identified as a mechanism for polar amplification.
context_section_description: In recent decades, sea ice in the Arctic Ocean has been melting faster than it re-freezes in winter.  The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report states that greenhouse gas forcing is predominantly responsible for the decline in Arctic sea ice extent. A 2007 study found the decline to be "faster than forecasted" by model simulations. 
  A 2011 study suggested that this could be reconciled by internal variability enhancing the greenhouse gas-forced sea ice decline over the last few decades.  A 2012 study with a newer set of simulations also projected rates of retreat which were somewhat less than that actually observed. 
  The IPCC Fifth Assessment Report concluded, with high confidence, that sea ice will continue to decrease in extent, and that there is robust evidence for the downward trend in Arctic summer sea ice extent since 1979. It has been established that the region is at its warmest for at least 4,000 years and the Arctic-wide melt season has lengthened at a rate of 5 days per decade (from 1979 to 2013), dominated by a later autumn freeze-up. Sea ice changes have been identified as a mechanism for polar amplification.
caption: Arctic sea ice extent anomaly.
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