Arctic Ice Minimum Earliest Since 1997

By Paul Homewood

http://nsidc.org/arcticseaicenews/

NSIDC seem pretty confident that Arctic sea ice extent has reached its minimum. According to them, it hit minimum on 11th September, but this is based on using the average of several days.

The actual minimum took place on 8th September:

ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/north/daily/data/NH_seaice_extent_nrt.csv

This in fact is unusually early. Apart from 2011, when it also occurred on the 8th, no other year has hit bottom as early since 1997. This is an indication of just how cold conditions there are.

This year’s extent is higher than 2007, 2011 and 2012. Perhaps NSIDC’s headline should have read “4th Highest in the Last Nine Years”!

Of course, it is weather conditions that have most effect on ice extent at this time of year, as even NSIDC admit:

Research has shown that especially low September sea extent tends to occur in years when the summer atmospheric circulation over the central Arctic Ocean is dominated by high atmospheric pressure, or anticyclonic conditions. This is because anticyclonic conditions tend to bring relatively sunny and warm conditions, and a clockwise wind pattern promotes ice convergence, making for a more compact, and thus smaller ice cover. The best example of this pattern occurred during the summer of 2007, which had the second lowest September extent in the satellite record. Conversely, Septembers with high extent tend to occur when the atmospheric circulation over the central Arctic Ocean is more cyclonic (counterclockwise), meaning unusually low pressure at the surface. This pattern brings more clouds, lower temperatures, and winds that spread the ice over a larger area.

Viewed in this framework, the pattern of atmospheric circulation for summer 2015 as a whole (June through August) favored a low September extent. Sea level pressures were higher than average over the central Arctic Ocean, as well as over Greenland and the surrounding region. Pressures were below average over north-central Eurasia. This was associated with air temperatures at the 925 hPa level (about 3,000 feet above the surface) that were above average over much of the Arctic Ocean, especially along the coast of eastern Siberia, in the Laptev Sea, and the Canadian Arctic Archipelago extending to the pole. However, it was not nearly as favorable as the 2007 pattern, when the area of unusually high pressure was located further south and east (over the northern Beaufort Sea), and unusually low pressure extended along much of the coast of northern Eurasia. This led to a pattern of warm winds from the south over the East Siberian and Chukchi Seas, promoting strong melt and transport of ice away from the coast. For both 2015 and 2007, the summer pressure patterns led to winds directed down the Fram Strait, helping to transport ice out of the Arctic Ocean into the East Greenland Sea.

http://nsidc.org/arcticseaicenews/2015/09/2015_arctic-minimum/

Meanwhile, Peter Wadhams’ ice free North Pole is there for all to see!