Some surprises in polar bear sea ice habitat at mid-October 2020


Reposted from Polar Bear Science

Posted on October 17, 2020 | 

Arctic sea ice has been growing steadily since the minimum extent was reached a month ago, with shorefast ice now developing along the Russian and Alaskan coastlines as ice cover expands in the Central Canadian Arctic. So while it’s true that the main pack of Arctic ice is far from the Russian shoreline, rapidly developing shorefast ice will allow bears to begin hunting seals long before ice in the central Arctic Basin reaches the Siberian shore, as they do in Western and Southern Hudson Bay every fall.

And speaking of Western Hudson Bay, it’s a very slow season around Churchill for problem polar bears (photo below) – the quietest mid-October for the Polar Bear Alert Program in the last five years and perhaps the quietest in decades (which I could say for sure if I had the records but I do not).

Average September sea ice cover was the second-lowest since 1979 but still within the 3-5mkm2 (see graph below) that polar bear experts wrongly predicted would cause the loss of 2/3 of the world’s polar bears (Crockford 2017, 2019, 2020):

ARCTIC SEA ICE THICKNESS

Compare above to 2012 on the same date, courtesy DMI below:

BEAUFORT SEA ICE VERY CLOSE TO SHORE

Soon the shorefast ice along the Southern Beaufort will meet up with the southward advancing pack ice and the region will again be ice-covered – after an ice-free period of less than 3 months – see 18 July 2020 chart below to see when the ice left the shore:

And what a difference a couple days makes! It literally took two days for a big change in Southern Beaufort Sea ice coverage. As the chart below from the Canadian Ice Service shows, by 17 October the Arctic pack mass was connected to rapidly-developing shorefast ice along the central coast of Alaska, which means that polar bears wishing to resume hunting have plenty of opportunity to do so beginning today:

BARENTS SEA LAGS BEHIND 2012 REFREEZE

Pack ice movement into the Barents Sea this year (image at top of post) is lagging behind 2012 (below) but not by much. It is likely to be only a few days before the ice reaches Franz Joseph Land as well as the archipelago of Severnaya Zemlya in the Kara Sea (middle of the image below, third group of islands east of Greenland). However, if 2012 is any indication, it will likely be early December before enough shorefast ice develops along the east coast of Novaya Zemlya (that long, skinny island upper right of image) – where all the bear trouble was in early 2019 – which will allow bears that spent the summer on shore to resume hunting (rather like Western Hudson Bay bears in a ‘late freeze-up’ year, see discussion below). It will be later than that (January/February?) before the Kara Sea will be filled with ice.

MEANWHILE IN WESTERN HUDSON BAY

No ice yet, of course – we wouldn’t expect ice in Hudson Bay even in the good old days of the 1980s. But the bears this year seem to be unusually mellow, content to patiently wait until freeze-up without causing much trouble, at least around Churchill. The situation might be shaping up differently in Arviat a bit further north. For your amusement, below is a video of a bear at Cape Churchill patiently killing time waiting for the sea ice:

The latest report on problem polar bears in Churchill for week 7 (below, 5-11 October) suggests a pretty boring time for Polar Bear Alert folks:

Forty-four incidents (‘occurrences’) as a cumulative total is very low for this time of year – and zero handled to date and zero in jail (the ‘holding facility’) is virtually unheard of. While last year (2019) was also a slow year for bear trouble in Churchill compared to other years, it was nowhere near as slow as this year:

Compare the last two years to 2018 (below), which was (like 2019) an early freeze-up year. In 2018, by the end of the second week in October there had already been 154 incidents, 8 bears in jail and 13 trapped and released locally:

In contrast, 2016 was the last year since that freeze-up was really late (i.e. early December) but because the bears came off the ice in great condition, by the second week in October the situation was no worse than 2018, when freeze-up was early:

Unless freeze-up is very late again this year – as it was in 1983 – this fall is shaping up to be something like 1984 in terms of polar bear problems in Churchill after a similarly late start to the season as this year (which began the last week of August). In the 1985 Polar Bear Specialist Group meeting report (Calvert et al. 1986:24), the problem bear situation in 1984 was described this way:

In 1984, the Polar Bear Control Programme season in Churchill was from 1 September to 2 November, more than a month shorter than the 1983 season. There were 69 reported incidents, and 200 man-days expended. There was one serious encounter – a mauling in which there appeared to be extenuating circumstances.” [my bold]

Time will tell and depends on whether freeze-up comes in early November as it did during most years (but notably not all) of the 1980s.

REFERENCES

Calvert, W., Stirling, I., Schweinsburg, R.E., Lee, L.J., Kolenosky, G.B., Shoesmith, M., Smith, B., Crete, M. and Luttich, S. 1986. Polar bear management in Canada 1982-84. In: Polar Bears: Proceedings of the 9th meeting of the Polar Bear Specialists Group IUCN/SSC, 9-11 August, 1985, Edmonton, Canada. Anonymous (eds). Gland, Switzerland and Cambridge UK, IUCN. http://pbsg.npolar.no/en/meetings/ pg. 19-34.

Crockford, S.J. 2017. Testing the hypothesis that routine sea ice coverage of 3-5 mkm2 results in a greater than 30% decline in population size of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 https://doi.org/10.7287/peerj.preprints.2737v3

Crockford, S.J. 2019The Polar Bear Catastrophe That Never Happened. Global Warming Policy Foundation, London. Available in paperback and ebook formats.

Crockford, S.J. 2020. State of the Polar Bear Report 2019. Global Warming Policy Foundation Report 39, London. pdf here.

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