![]() Viewed in this framework, the pattern of atmospheric circulation for summer 2015 as a whole (June through August) favored a low September extent. This pattern brings more clouds, lower temperatures, and winds that spread the ice over a larger area. Conversely, Septembers with high extent tend to occur when the atmospheric circulation over the central Arctic Ocean is more cyclonic (counterclockwise), meaning unusually low pressure at the surface. The best example of this pattern occurred during the summer of 2007, which had the second lowest September extent in the satellite record. This is because anticyclonic conditions tend to bring relatively sunny and warm conditions, and a clockwise wind pattern promotes ice convergence, making for a more compact, and thus smaller ice cover. Research has shown that especially low September sea extent tends to occur in years when the summer atmospheric circulation over the central Arctic Ocean is dominated by high atmospheric pressure, or anticyclonic conditions. The patterns for 2015 contributed to low September extent, but were not as favorable for producing low extent as the patterns seen in 2007.Ĭredit: NOAA/ESRL Physical Sciences Division This figure shows patterns of sea level pressure and air temperature at the 925 hPa level for the summers (June through August) of 2015 and for 2007, expressed as differences from the 1981 to 2010 average. How long they remain open depends on weather patterns and the amount of heat still present in the ocean mixed layer (about the top 50 feet of the ocean). The deeper and wider Northwest Passage route through Parry Channel, which consists of M’Clure Strait, Barrow Strait, and Lancaster Sound, still has some ice in it. Moreover, the nine lowest extents in the satellite era have all occurred in the last nine years.īoth the Northern Sea Route, along the coast of Russia, and Roald Amundsen’s route through the Northwest Passage are open. The extent ranked behind 2012 (lowest), 2007 (second lowest), and 2011 (third lowest). The minimum extent was reached four days earlier than the 1981 to 2010 average minimum date of September 15. However, a shift in wind patterns or a period of late season melt could still push the ice extent lower. In response to the setting sun and falling temperatures, ice extent will now climb through autumn and winter. This appears to be the lowest extent of the year. On September 11, 2015, sea ice extent dropped to 4.41 million square kilometers (1.70 million square miles), the fourth lowest minimum in the satellite record. About the dataĬredit: National Snow and Ice Data Center The black cross indicates the geographic North Pole. The orange line shows the 1981 to 2010 average extent for the day. ![]() Arctic sea ice extent for September 11, 2015, was 4.41 million square kilometers (1.70 million square miles). ![]()
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