Climate Change Indicators: Arctic Sea Ice
Key PointsSeptember 2012 had the lowest sea ice extent ever recorded, 44 percent below the 1981–2010 average for that month.The September 2016 sea ice extent was more than 700,000 square miles less than the historical 1981–2010 average for that month (see Figure 1)—a difference more than two and a half times the size of Texas. March sea ice extent reached the lowest extent on record in 2015 and hit roughly the same low again in 2016—about 7 percent less than the 1981–2010 average.All months have shown a negative trend in sea ice extent over the past several decades. The largest year-to-year decreases have occurred in the summer and fall months.2,3Evidence of the age of Arctic sea ice suggests that fewer patches of ice are persisting for multiple years (i.e., generally thick ice that has survived one or more melt seasons) (see Figure 2). The proportion of sea ice five years or older has declined dramatically over the recorded time period, from more than 30 percent of September ice in the 1980s to 9 percent in 2015. A growing percentage of Arctic sea ice is only one or two years old. Less old multi-year ice implies that the ice cover is thinning, which makes it more vulnerable to further melting.Since 1979, the length of the melt season for Arctic sea ice has grown by 37 days (see Figure 3). Arctic sea ice now starts melting 11 days earlier and it starts refreezing 26 days later than it used to, on average (see Figure 3).
References1. IPCC (Intergovernmental Panel on Climate Change). 2013. Climate change 2013: The physical science basis. Working Group I contribution to the IPCC Fifth Assessment Report. Cambridge, United Kingdom: Cambridge University Press. www.ipcc.ch/report/ar5/wg1.2. NSIDC (National Snow and Ice Data Center). 2012. Arctic sea ice 101. http://nsidc.org/icelights/arctic-sea-ice.3. Comiso, J. 2012. Large decadal decline of the Arctic multiyear ice cover. J. Climate 25(4):1176–1193.4. NSIDC (National Snow and Ice Data Center). 2016. Sea ice data and image archive. Accessed October 2016. http://nsidc.org/data/seaice_index/archives.html.5. NSIDC (National Snow and Ice Data Center). 2015. Arctic sea ice news and analysis. October 6, 2015. http://nsidc.org/arcticseaicenews/2015/10/2015-melt-season-in-review6. NASA (National Aeronautics and Space Administration). 2016. Arctic sea ice melt. https://neptune.gsfc.nasa.gov/csb/index.php?section=547. NASA (National Aeronautics and Space Administration). 2016. NASA’s Goddard Space Flight Center Scientific Visualization Studio. https://svs.gsfc.nasa.gov
