The National Snow and Ice Data Center (NSIDC) issued figures confirming that while sea ice extent in the Chukchi and Beaufort Seas remains below average, extent remains especially low on the Atlantic side of the Arctic in the Barents and Laptev Seas. October sea ice extent in the Arctic was the third lowest in the satellite record, averaging 6.06 million square kilometers (2.34 million square miles).
Key figures for October 2018
- Arctic sea ice extent for October 2018 averaged 6.06 million square kilometers (2.34 million square miles), the third lowest October extent in the 1979 to 2018 satellite record.
- This was 2.29 million square kilometers (884,000 square miles) below the 1981 to 2010 average, and 170,000 square kilometers (66,000 square miles) above the record low recorded for October 2012.
- Sea ice gain during the first half of the month was quite slow. By the third week of October, extent was still tracking below all years except 2016. However, toward the end of the month, the pace of ice growth increased.
- Ice growth through the month was strong in the Beaufort and Chukchi Seas, but extent remained below average in these areas at the end of the month.
A large area of open water remained in the Laptev Sea, which is unprecedented in the satellite record at the end of October. Especially prominent was the lack of ice growth on the Atlantic side of the Arctic in the Barents Sea, and in some regions, a slight contraction of the ice edge further north. As a result, extent is presently far below average in this area, and is the primary reason why October extent for the Arctic as a whole is third lowest on record.
- October air temperatures at the 925 hPa level (about 2,500 feet above the surface) were above average across nearly all of the Arctic Ocean, but especially high temperatures—5 to 7 degrees Celsius (9 to 13 degrees Fahrenheit) above average—were found over the Beaufort and Chukchi Seas and extending poleward. The most extreme warmth was located over central Alaska, where temperatures were up to 7 degrees Celsius (13 degrees Fahrenheit) higher than average.
October 2018 compared to previous years
- Sea ice extent for October 2018 fell below the long-term linear trend line. The linear rate of sea ice decline for October is 79,000 square kilometers (31,000 square miles) per year, or 9.5% per decade relative to the 1981 to 2010 average.
- Another notable feature in the Arctic ice pack at the end of October was the significant amount of open water in the Laptev Sea. Even in 2007 and 2012, the previous record low minimum extent years, the Laptev had nearly completely frozen over by the end of October. As late as October 29, the Laptev sea ice extent was less than 500,000 square kilometers (193,000 square miles). The 1981 to 2010 average extent on that date is 870,000 square kilometers (336,000 square miles)—essentially the entirety of the defined Laptev Sea region. By mid-October, the long-term average sea ice extent exceeds 800,000 square kilometers (309,000 square miles). This year, the mid-October sea ice extent within the Laptev Sea was barely above 100,000 square kilometers (39,000 square miles), about 13% of average.
The cause of this lack of ice is multifaceted. Ocean heat gained during the summer is likely delaying freeze-up. As noted above, air temperatures were above average over the region. This may in part be a result of the ocean heat, though low pressure centered over the Barents and Kara Seas also brought in warm air and winds from the south, keeping the ice edge from advancing.
Antarctic sea ice
- Antarctica’s annual maximum sea ice extent of 18.15 million square kilometers (7.01 million square miles) was reached on October 2, the fourth lowest maximum in the satellite record.
- Antarctic sea ice extent for October 2018 averaged 17.66 million square kilometers (6.82 million square miles), also the fourth lowest in the satellite record.
- Sea ice extent was particularly low in the sector south of Australia, south of Africa, and in the Bellingshausen and Amundsen Seas. Locations and sizes of these regional features varied through the course of the month as storms and strong winds shifted.
- Air temperatures at 925 hPa were 3 to 6 degrees Celsius (5 to 11 degrees Fahrenheit) above the 1981 to 2010 average in West Antarctica and the southern Antarctic Peninsula, and 2 to 3 degrees Celsius (4 to 5 degrees Fahrenheit) above average over a wide part of the Bellingshausen and Amundsen Seas. However, temperatures in the Weddell Sea region were 2 to 6 degrees (4 to 11 degrees Fahrenheit) below average.
