The sun has set over the central Arctic Ocean and Arctic sea ice extent is now increasing. Sea ice extent in Antarctica appears to have passed its seasonal maximum according to National Snow & Ice Data Center (NSIDC). The peak Antarctic value recorded so far of over 20 million square kilometers (7.7 million square miles) sets a new record over the period of satellite observations.
Overview of conditions
Following the seasonal daily minimum of 5.02 million square kilometers (1.94 million square miles) that was set on September 17, 2014 (6th lowest in the satellite record), Arctic sea ice has started its seasonal cycle of growth. Arctic sea ice extent averaged for the month of September 2014 was 5.28 million square kilometers (2.04 million square miles), also the 6th lowest in the satellite record. This is 1.24 million square kilometers (479,000 square miles) below the 1981 to 2010 average extent, and 1.65 million square kilometers (637,000 square miles) above the record low monthly average for September that occurred in 2012.
Conditions in context
Because ice extent falls through the first part of September and rises in the latter part, statistics on the average daily rate of ice loss or gain through the month are largely meaningless. More relevant is the total ice loss through the melt season. Between the seasonal maximum extent that occurred on March 21, 2014 and the September 17 minimum, the Arctic Ocean lost a total of 9.89 million square kilometers (3.82 million square miles) of ice, which is the 9th largest in the satellite record, but the least amount of seasonal loss since 2006. This year’s loss was 1.92 million square kilometers 741,000 square miles) less than the total loss that occurred in 2012.
September 2014 compared to previous years
Through 2014, the linear rate of decline for September Arctic ice extent over the satellite record is 13.3% per decade, relative to the 1981 to 2010 average. The ten lowest September ice extents over the satellite record have all occurred in the last ten years.
Summer weather conditions in 2014
Weather conditions prevailing over the summer of 2014 were unremarkable. Compared to the long term (1981 to 2010) climatology, sea level pressure over the period June through August was higher than average over much of the central Arctic Ocean, the Atlantic sector of the Arctic, and Greenland. While air temperatures at the 925 hPa level (approximately 3000 feet altitude) were slightly above average over part of the central Arctic Ocean, they were below average over the Kara Sea and just north of Alaska. The summer of 2013, which is now the 7th lowest ice extent in the satellite record, was also generally unremarkable in terms of temperature. Both of these years contrast sharply with 2012, which saw unusually warm conditions across the Arctic Ocean. The one significant weather pattern over the summer was a larger than normal pressure gradient over the Laptev Sea that drove southerly winds, brought warmer air, and helped drive sea ice northward. This led to the tongue of open water that reached to within 5 degrees latitude of the pole. However, this pressure gradient was not particularly extreme so thinner ice cover in the area was also a significant contributor to the open water near the pole. Sea surface temperatures may also have played a role.
Sea Ice maximum in Antarctica
As we reported in our Arctic minimum announcement, sea ice in Antarctica has remained at satellite-era record high daily levels for most of 2014. On September 22, 2014, Antarctic ice extent increased to 20.11 million square kilometers (7.76 million square miles). This was the likely maximum extent for the year.
This year’s Antarctic sea ice maximum was 1.54 million square kilometers (595,000 square miles) above the 1981 to 2010 average maximum extent, which is nearly four standard deviations above this average. The 2014 ice extent record is 560,000 square kilometers (216,000 square miles) above the previous record ice extent set on October 1, 2013. Each of the last three years (2012, 2013, and 2014) has set new record highs for extent in the Antarctic.
The monthly average Antarctic ice extent for September 2014 is 20.03 million square kilometers (7.73 million square miles). This is 1.24 million square kilometers (479,000 square miles) above the 1981 to 2010 average for September ice extent. The Antarctic sea ice trend for September is now +1.3% per decade relative to the 1981 to 2010 average.
Monthly averaged ice extent for September is well above average in the western Pacific (northern Ross Sea) and Indian Ocean (Enderby Land) sectors.
A related note
Last year, a vessel became trapped in ice south of Australia in an incident that highlighted the need for better local ice forecasts. The International Ice Charting Working Group will meet later this month in Punta Arenas, Chile. Members will work on improving the collective capability of ice services to provide ice information in the interests of marine safety.
Source and Image Credit: National Snow & Ice Data Center
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