Polar bear habitat update and the progress of breakup on Hudson Bay

At mid-month, there is still an abundance of thick first year ice over much of Hudson Bay, suggesting that – yet again – this will not be an early breakup year for Western Hudson Bay polar bears. The early breakup years in the past (like 2010) that generated all kinds of panic amongst polar bear specialists have not developed into ever-continuing declining trend (Lunn et al. 2016) or another abrupt step-change like there was in 1998/99 (Castro de la Guardia et al. 2017).

In the last few years conditions have been more like they were in the 1980s than the prophesied catastrophe we were promised. I don’t see a ‘tipping point’ for Hudson Bay; do you see a tipping point?

The more light green areas of thinner ice present, as there was in 2010 (below), the earlier breakup is apt to be:

According to Andrew Derocher (University of Alberta), the bears that still have operational satellite collars are still on the ice and most were still well offshore at 14 June 2021:

Compare the above weekly charts of ice thickness to mid-June charts from the last few years. I don’t have the chart from last year at this time because it was moving day for me and life was rather chaotic.

Unfortunately, there hasn’t been any published data on dates when WH polar bears have moved onshore and offshore since 2015 (Castro de la Guardia et al. 2017), which is the relevant determiner of ‘breakup’ for the bears. Maybe they’ve just been too busy? However, most WH researchers haven’t been able to do any field work since last spring and have had all the time in the world to write up their data from previous years. So perhaps we’ll see this critical WH data soon.

Ice thickness at mid-June 2019:

And from 2018:

From 2016:

And finally, 2015:


Castro de la Guardia, L., Myers, P.G., Derocher, A.E., Lunn, N.J., Terwisscha van Scheltinga, A.D. 2017. Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Series 564: 225–233. http://www.int-res.com/abstracts/meps/v564/p225-233/

Lunn, N.J., Servanty, S., Regehr, E.V., Converse, S.J., Richardson, E. and Stirling, I. 2016. Demography of an apex predator at the edge of its range – impacts 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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