Arctic sea ice is spreading out quickly from its central basin summer refuge – according to this NSIDC Masie ice chart, it has already grown more than 2 mkm2 beyond the annual minimum reached in early September. Ice is already pushing south into the eastern Beaufort and the archipelago of Franz Josef Land in the Barents Sea.
Over the next couple of weeks, shorefast ice will start forming along the coasts of North America and Eurasia (see the first bits off Alaska in the 21 October CIS map below), which will eventually meet the expanding Arctic Basin pack to fill the Basin and Canadian Arctic Archipelago with ice – as it has done for eons.
The evidence from the last decade or so suggests that by the end of October, most of the Arctic north of the 79th parallel (see map below) will be filled with ice – although the Chukchi Sea (north of the Bering Strait) may not fill until sometime in November:
Polar bears usually resume hunting as soon as sea ice conditions permit in the fall, since it’s their last chance to top up their fat reserves before the dark and cold of winter when hunting may become next to impossible.
I’ve copied ice charts from the Masie archives for some previous years at 31 October below.
Last year (2015), there was 9.0 mkm2 of ice at 31 October but much of the Chukchi Sea was essentially ice-free, as the chart below shows.
In 2013 (the last year of published polar bear data for the Chukchi Sea, see Rode et al. 2015), there was slightly more ice in that region than in 2015:
However, in 2012 (the lowest September minimum since 1979), there was little ice in the Beaufort Sea and none surrounding the islands of Franz Josef Land in the Barents Sea at 31 October.
In 2007 (which had a similar September minimum as 2016), it was the Chukchi Sea that was virtually ice-free – and Franz Josef Land was virtually surrounded by ice.
Since there is already more ice in the Beaufort and Chukchi Seas (at 20 October) than there was at 31 October 2007 and 2012, it looks like 2016 may show a different pattern again.
Compare all of the above to 31 October 2006 (the earliest year for which these charts are available):
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