From polar bear science
Posted on June 17, 2021 June
By mid-month there is still an abundance of thick first year ice over much of Hudson Bay, suggesting this – once again – will not be an early breakup for western Hudson Bay polar bears. The early years of separation in the past (such as 2010), which caused all kinds of panic among polar bear specialists, did not develop into a steadily declining trend (Lunn et al. 2016) or another abrupt leap like 1998/99 (Castro de la Guardia et al. 2017).
In recent years, conditions have been more like the 1980s than the prophesied disaster we were promised. I don’t see a turning point for Hudson Bay; do you see a tipping point?
The more bright green areas with thinner ice there, as was the case in 2010 (below), the sooner the resolution is likely:
According to Andrew Derocher (University of Alberta), the bears that still have working satellite collars are still on the ice and most were far offshore as of June 14, 2021:
Compare the weekly ice thickness maps above with the mid-June maps of recent years. I don’t have last year’s charts at this point because it was a moving day for me and life was pretty chaotic.
Unfortunately, since 2015 there has been no published data on the dates when GH polar bears moved on land and at sea (Castro de la Guardia et al. 2017), which is the relevant factor for the “breakup” of the bears. Maybe they were just too busy? However, most WH researchers have not been able to do field research since last spring and had all the time in the world to write down their data from previous years. So maybe we’ll see this critical GH data soon.
Ice thickness in mid-June 2019:
And from 2018:
From 2016:
And finally, in 2015:
References
Castro de la Guardia, L., Myers, PG, Derocher, AE, Lunn, NJ, Terwisscha van Scheltinga, AD 2017. Sea ice cycle in western Hudson Bay, Canada, as seen by a polar bear. Marine Ecology Progress Series 564: 225-233. http://www.int-res.com/abstracts/meps/v564/p225-233/
Lunn, NJ, Servanty, S., Regehr, EV, Converse, SJ, Richardson, E. and Stirling, I. 2016. Demographics of a top predator on the edge of its range – Effects of changing sea ice on polar bears in Hudson Bay. Ecological Applications 26 (5): 1302-1320. DOI: 10.1890 / 15-1256
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