After a quick initial freeze-up during the second half of September, ice growth slowed substantially during early October. On October 20, 2016, Arctic sea ice extent began to set new daily record lows for this time of year. After mid-October, ice growth returned to near-average rates, but extent remained at record low levels through late October. High sea surface temperatures in open water areas were important in limiting ice growth. October air temperatures were also unusually high, and this warmth extended from the surface through a considerable depth of the atmosphere.
In October 2016, Arctic sea ice extent averaged 6.40 million square kilometers (2.5 million square miles), the lowest October in the satellite record. This is 400,000 square kilometers (154,400 square miles) lower than October 2007, the second lowest October extent, and 690,000 square kilometers (266,400 square miles) lower than October 2012, the third lowest. The average extent was 2.55 million square kilometers (980,000 square miles) below the October 1981 to 2010 long-term average.
As of early November, extent remains especially low within the Beaufort, Chukchi, East Siberian, and Kara Seas. Since the beginning of October, ice growth occurred primarily in the Laptev Sea, stretching from the New Siberian Islands towards the coast. Little ice growth occurred in the Kara and Barents Seas, while ice extent increased in the Chukchi and Beaufort Seas.