From Polar Bear Science
Susan Crockford
Although sea ice experts predict that catastrophic declines could occur any year now, polar bear habitat in June, the last month of Arctic spring, remains within 2 standard deviations of the long-term average.
Arctic sea ice cover retreated at a slower than average rate in June 2024, causing the total sea ice area during the month to be larger than in recent years. NSIDC, July 3, 2024
Oddly, the National Snow and Ice Data Center (NSIDC) staff who wrote the June sea ice summary thought it appropriate to base the recently released prediction of the imminent extinction of polar bears in the Southern Hudson Bay on sea ice forecasts (Stroeve et al., 2024) , which I introduced here . The inclusion of this topic is a blatant promotion of Stroeve's sea ice model paper, which not only does not match the reality of this year's sea ice conditions, but their discussion does not include any evidence of the arrival of polar bears in the southern Hudson Bay .
arctic summary
Here is the NSIDC chart for sea ice in June:
The area in June this year was 10.9 mkm2. Compared with previous years, it was basically the same as in 2006 and slightly lower than last year, as shown in the figure below:
south hudson bay
The NSIDC report stated: “The average date of ice retreat in southern Hudson Bay is mid-June to late July, so there is usually enough ice for polar bears to hunt ringed seal pups, their main food source. If the ice melts too early, as it has this year, bears will be stranded on land for much of the summer and fall, extending their annual fasting period”.
First, polar bears do not “hunt ringed seal pups” in Hudson Bay from mid-June to late July. By then, the seal pups had been weaned and were feeding in open waters. The only potential prey are adult and sub-adult seals, which may inhabit the sea ice while they molt, but it is very rare for bears to successfully hunt these older seals because they are more experienced and able to remain alert to predators. The reader knows everything. As I've pointed out countless times, polar bears might stay on the ice until July or even August if they could, but that's not to hunt seals.
Additionally, there was still ice in James Bay on June 18 (see photo below), so ice breaks were not uncommon, and there was still a lot of ice on the southwest coast of Hudson Bay, with many SH bears crawling out of the ice.
In fact, there is still a lot of ice on the southwestern shore of Hudson Bay all the way to western Hudson Bay, and it's almost mid-July! A close-up of the Hudson Bay sea ice map shown below is what it looked like on July 10, with ice still on the coast of the Southern Hudson Bay subpopulation area:
In other words, despite the large swaths of open water in eastern Hudson Bay in May, all indicators point to this not being the year for early sea ice breakup in southern Hudson Bay for polar bears.
In case I didn't point out, the dire consequences of the early breakup model for bears in the southern Hudson Bay contradict an earlier study suggesting that only late freezes would negatively impact this subpopulation (Obbard et al., 2016), then I would be remiss.
Here's what Obade and colleagues have to say about the relationship between bear physical condition and sea ice in southern Hudson Bay (my bold):
“In our study, the freeze date had a greater impact on subsequent physical outcomes than the breakup date. …we believe that the stronger effect of freeze dates may be due to Although rupture has been advanced by 3-4 weeks in parts of the Hudson Bay, it still won't happen earlier than late June or early July Therefore, feeding opportunities for newborn ringed seal pups born in March to April in eastern Hudson Bay will not be affected at this time. So losing days or weeks of hunting opportunities in June and July deprives polar bears of the opportunity to feed on adult seals, but it doesn't deprive them of the critical spring period when they can really eat voraciously. There is no doubt that losing the opportunity to hunt adult seals will have a negative impact on body condition, but It appears that, for Shanghai bears, being forced to extend their fasting in late autumn would have a greater negative impact on subsequent physical condition.” [my bold]
western hudson bay
By the end of June this year, all but one bear tagged by the University of Alberta in western Hudson Bay was still on the ice:
Note that the “behavioral plasticity” Drocher mentioned above refers to a pattern since at least 2015 in which polar bears have been staying on melting sea ice far beyond what “experts” previously insisted would lead to The stage when polar bears abandon the ice. Their sea ice/polar bear survival models all rely on this failed assumption, including Stroeve's paper.
It became increasingly difficult for Derocher and his colleagues to ignore the fact that their assumptions about sea ice concentration and polar bear behavior were simply wrong. This year, some white bears may remain on the ice again until August, although on paper this is the earliest year ever for sea ice to break up in the Hudson Bay.
refer to
Obbard, ME, Cattet, MRI, Howe, EJ, Middel, KR, Newton, EJ, Kolenosky, GB, Abraham, KF, & Greenwood, CJ 2016. Trends in polar bear body condition (sea bear) from the southern Hudson Bay subpopulation in relation to sea ice changes. arctic science, in the news. 10.1139/AS-2015-0027
Stroeve, J., Crawford, A., Ferguson, S., Stirling, I., Archer, L., York, G., Babb, D., & Mallet, R. 2024. If global warming exceeds 1.6 to 2.6, ice-free periods will be too long for polar bear populations in southern and western Hudson Bay0 C. Nature Communications Earth & Environment 5:296 [open access] https://doi.org/10.1038/s43247-024-01430-7
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