Fall polar bear habitat update: 3 mkm2 Arctic sea ice increase in the last two weeks

What a difference two weeks make! When the seasonal minimum Arctic sea ice extent occurs in September, polar bear doom-mongers always forget to tell you that within two months, sea ice will return to virtually all regions where polar bears have spent the summer on land, including Hudson Bay. Just as it did in 2007, when polar bears did not die by the thousands due to lack of fall sea ice, polar bear habitat is reforming.

Polar bear tests thin ice_Laidre_UW_no copyright_taken22August2015_sm

This year, the seasonal minimum came on 23 September. Despite the fact that the US National Snow and Ice Data Center proclaimed that “unusual warmth” in the Arctic continued during October, over the last two weeks sea ice expanded from 6 mkm2 to 9 mkm2. At the current rate of ice growth documented by sea ice charts (see below), Arctic sea ice will be wide-spread by 23 November.

NSIDC’s Masie ice chart for 22 October:

masie_all_zoom_4km 2018 Oct 22

And two weeks later, on 5 November:

masie_all_zoom_4km 2018 Oct 5

Compare the chart above to 2014 on the same date (below), when the ice reached exactly the same level (in terms of total extent), but the distribution was somewhat different: less ice in Baffin Bay but more in the Barents and Kara Seas.

masie_all_zoom_v01_2014309_4km

Fall sea ice growth pattern

Sea ice extent on 16 September 2007 (the seasonal minimum):

IDL TIFF file

Sea ice extent on 14 November 2007 (below), about two months later, where only bears onshore along Hudson Bay, southern Baffin Island and Svalbard were waiting for sea ice to form along the coast:

IDL TIFF file

All well-fed polar bears are capable of surviving a 5 month long fast whether they spend that time on land (like Western Hudson Bay bears do) or on the sea ice (like many Chukchi and Barents Sea bears do).

But in the only region of the Arctic that an abnormally long summer fast (>5 months) might have been necessary in recent years (south-eastern Svalbard), virtually all bears have shifted to Franz Josef Land or remain on the sea ice year round (since bears can, and do, spend their entire lives on the sea ice).

Barents Sea bears do not require the denning areas in eastern Svalbard to thrive as long as Franz Josef Land retains its ice cover from fall to late summer as it has done since 2007.

Hudson Bay ice

Polar bears off Churchill_2000-11-20_wikipedia

Sea ice is forming slowly along Western Hudson and James Bays: the ice that formed along shore in late October indeed blew offshore or was broken up by waves as I warned it might:

Hudson Bay North daily stage of development 2018 Oct 23 new ice

Now new ice is reforming:

Hudson Bay NW daily stage of development 2018 Nov 6

Not only in the north, but in the southern reaches of Hudson and James Bay have new ice as well:

Hudson Bay South daily stage of development 2018 Nov 6

This ice should thicken and expand over the next few weeks. Adult bears can start hunting even before the ice reaches the grey stage (10-15 cm thick, dark purple on the charts), see the charts from last year here.

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