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Arctic sea ice reaches minimum for year, 8th lowest since 1979
On Sept. 13 the extent of sea ice in the Arctic appeared to reach its minimum for this year, the National Snow and Ice Data Center has reported. Although it is possible that a late-season melt could reduce the ice extent further, it is likely that the Sept. 13 extent of 1.79 million square miles will prove to be the minimum. That minimum level was the eighth lowest level since satellite observations began in 1979. It was 610,000 square miles less than the median extent for the same day between 1981 and 2010, but 193,000 square miles above the 2012 to 2016 extents, NSIDC said. The rate of ice loss in early September was slightly higher than the 1981 to 2010 average.
The 10 lowest ice extents measured from satellite tracking have all been observed since 2010.
NSIDC reported that the Arctic sea ice edge continued to retreat in the Chukchi, East Siberian and Kara seas during the first two weeks of September, but expanded slightly in the Beaufort and Laptev seas during the same time period. The ice edge is far north of its average position in the Chukchi Sea.
Navigation possible The Northern Sea route around the north coast of Russia is largely open. However, Amundsen’s Northwest Passage, the more southerly route around northern Canada, has up to 50 percent sea ice cover in some places. The more northerly Northwest Passage, through the McClure Strait, is blocked by consolidated, thick, multi-year ice.
Some ships have successfully navigated the southern Northwest Passage using icebreaker assistance, NSIDC said. According to the Crystal Cruises website, the cruise ship Crystal Serenity successfully transited the Northwest Passage for a second year in late August/early September. The Crystal Serenity was escorted by the icebreaker Ernest Shackleton.
Low air pressure NSIDC said that this year a pattern of low air pressure at sea level across the central Arctic Ocean inhibited summer sea ice loss. However that pattern changed in the first half of September, with above average pressure over the Barents Sea and part of the Arctic Ocean.
NSIDC also reported that an analysis of the Chukchi Sea and Beaufort Sea ice extent conducted by the National Weather Service in Fairbanks found that the 2017 extent tracked near record lows for the region through most of the summer. However, the pace of ice loss slowed relative to recent years after mid-August. The minimum ice extent in this region tends to occur later than for the Arctic as a whole, but it appears likely that the Chukchi/Beaufort minimum extent this year will be among the four or five lowest on record.
Apparently the National Weather Service has predicted that because of extensive open water, air temperatures over the Beaufort and Chukchi seas and along the North Slope will probably be far above average through the autumn.
Meanwhile, in the Antarctic the sea ice extent is approaching its winter maximum, an extent that looks likely to be among the five lowest recorded during the era of satellite observation, NSIDC said.
- ALAN BAILEY
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