Above-average temperatures lead to lowest ever Arctic sea ice cover

by Search Gate staff. Published Fri 20 Mar 2015 13:51, Last updated: 2015-03-20
Scientists report record-low winter ice cover
Scientists report record-low winter ice cover

This winter’s Arctic sea ice cover is the lowest on record as satellite image studies reveal the polar region is now over a million square kilometres of ice down from 30-year averages.

According to the US National Snow and Ice Data Centre (NSIDC), Arctic sea ice likely reached its maximum extent for the year on February 25 at 14.54 million square kilometers (5.61 million square miles).

This year’s maximum ice extent was the lowest in the satellite record, with below-average ice conditions everywhere except in the Labrador Sea and Davis Strait. The maximum extent is 1.10 million square kilometers (425,000 square miles) below the 1981 to 2010 average of 15.64 million square kilometers (6.04 million square miles) and 130,000 square kilometers (50,200 square miles) below the previous lowest maximum that occurred in 2011.

This year’s maximum occurred 15 days earlier than the 1981 to 2010 average date of March 12. The date of the maximum has varied considerably over the years, occurring as early as February 24 in 1996 and as late as April 2 in 2010.

Because of the variability of ice extent at this time of year, there can be some delay in pinpointing the date of the maximum extent. NSIDC calculates daily ice extent as an average of the previous five days, and they also look for a clear downward trend for a number of days.

While the downturn in extent was quite pronounced on February 25, the trend subsequently flattened. This is in part due to recent ice growth in the Bering Sea, partly balancing continued ice retreat in the Barents and Kara seas. Over the next two to three weeks, periods of increase are still possible. However, it now appears unlikely that there could be sufficient growth to surpass the extent reached on February 25.

Over the 2014 to 2015 winter season, sea ice extent grew 9.91 million square kilometers (3.83 million square miles). This was substantially less ice growth than last year, which saw record growth over the winter. Part of the explanation for the record low maximum lies with recent weather patterns.

February was characterized by an unusual configuration of the jet stream, leading to warm conditions over the Pacific side of the Arctic that maintained low sea ice extent in the Bering Sea and the Sea of Okhotsk.

Furthermore, since the last half of February through the middle of March, the Arctic Oscillation was in a strongly positive phase, with index values exceeding 5.0 for several days in the first week of March.

This has been expressed as a strong Icelandic Low, a semi-permanent area of low atmospheric pressure found between Iceland and southern Greenland and extending into the Barents Sea. The strong Icelandic Low led to a pattern of surface winds over the Barents and Kara seas with an unusually strong component from the south.

Over the first two weeks of March, temperatures throughout the eastern Arctic at the 925 hPa level (approximately 3,000 feet altitude) were several degrees Celsius above average, with temperatures as much as 8 to 10 degrees Celsius (14 to 18 degrees Fahrenheit) above average in the Barents Sea between Svalbard and Franz Josef Land.

While the seven-day weather forecasts show continued warmer-than-average conditions over the eastern Arctic, colder-than-average conditions are expected over the Bering Sea and may still lead to some new ice formation. Thus, while the maximum appears to have occurred on February 25, late season ice growth may still occur.

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