The freeze is on: from an annual low of ~5.1 m sq km at 15 September 2014, the sea ice that provides a hunting platform for polar bears is rapidly reforming.
Note that polar bear habitat world-wide is pretty well defined by the extent of sea ice in spring, with three notable exceptions. There are no polar bears (or fossil evidence of polar bears), in the Sea of Okhotsk, the Gulf of St. Lawrence, or the Baltic Sea.
Bears in some areas spend time on land in late summer/early fall but the amount of time varies widely.
Have a look at the maps below: the difference in regional coverage between the sea ice at 4 August and 16 October (73 days apart, both covering 7.3 mkm2) might surprise you.
In this part of my critique of Stirling and Parkinson (2006), regarding breakup dates in Western Hudson Bay (see Part I here), I will show that these authors also left out critical data.
Figure 1. A bear is transported to Churchill’s polar bear holding facility, from a 2011 Huffington Post article “Polar Bear Prison.”
Their correlation between number of problem bears in Churchill and breakup dates for WHB worked because some very inconvenient data were simply left out: problem bear data for 1983 and 2004.
Inclusion of that information would have shown 1983 and 2004 were two of the worst years for polar bear problems in recent history despite being late breakup years (1983 also had the last human fatality from a polar bear attack). They could have explained why they did not use the data but they did not — they simply left it out.
Amazingly, this work is being touted as “evidence” that global warming is harming Western Hudson Bay polar bears.
Posted in Advocacy, Polar bear attacks, Sea ice habitat
Tagged breakup, cherry-picking, Churchill, correlation, Derocher, early breakup, fatal attack, freeze-up, Kearney, less than healthy science, Ockham's Broom, Parkinson, polar bear, problem bears, Stirling, Towns, western hudson bay
Yes, I wondered too. After all the kerfuffle at the beginning of the month there’s been rather dead silence [see my last post here]. So I Googled and found some tidbits.
Chukchi Sea walrus, June 2014. US Fish and Wildlife Service.
An article a few days ago at one media outlet (October 8, 2014) asked someone from the WWF what happened to the ~35,000 females and calves onshore near Point Lay, Alaska — because really, who else would you ask? Or, perhaps more to the point, would anyone at USGS be expected to answer?
And one online media outlet found walrus specialists in Alaska unwilling to lay all the blame for the recent massive haulout at Point Lay at the feet of low Arctic ice levels due to global warming. See what you think.
UPDATE added below October 13, 2014
Posted in Advocacy, Sea ice habitat, walrus
Tagged Alaska, haulouts, Lara Horstmann, media hype, Nicole Misarti, Point Lay, stampedes, USGS, walrus, World Wildlife Fund, WWF
The oft-repeated claim that polar bears are starving in Western Hudson Bay (e.g., here, here, here, and here) comes primarily from a 10 year old study that documented a declining trend in polar bear body condition (a biology euphemism for relative fatness) between 1980 and 2004, which appeared to correlate with earlier and earlier breakup dates for Hudson Bay.
Figure 1. Polar bear female with cub, 2009, Churchill, Western Hudson Bay. Wikipedia.
The authors of that study (polar bear specialist Ian Stirling and NASA sea ice researcher Claire Parkinson) reported the body weights of lone female bears captured in Western Hudson Bay between 1980 and 2004. The trend over time in those bear weights was then correlated with the overall change in dates of sea ice breakup on Hudson Bay for that period.
However, it turns out that while the trend of body condition and the trend in breakup dates indeed correlated over time, the actual year to year data did not. The question is, what does that mean for the claim that polar bears in WHB are starving?
Posted in Life History, Sea ice habitat
Tagged body condition, breakup, Cherry, climate change, Parkinson, pregnancy, sea ice, starving polar bears, Stirling, too thin, trends, weight, western hudson bay
Here is the September 2014 follow-up to my post on the July 2013 track map for female polar bears being followed by satellite in the Beaufort Sea by the US Geological Survey (USGS) – “Ten out of ten polar bears being tracked this summer in the Beaufort Sea are on the ice.”
See that post for methods and other background on this topic, and some track maps from 2012 (also available at the USGS website here).
The USGS track map for September 2014 is copied below (Fig. 1).
At the end of September, with sea ice starting to rebuild, it appears there were 8 bears on the ice and three on land.
The situation for September was not very much different from August, except that two of the 11 bears (up from one) were on the ice in the Chukchi Sea in September, a phenomenon that was recently acknowledged to have affected the last population estimate for the Southern Beaufort subpopulation.
Posted in Population, Sea ice habitat
Tagged Alaska, Beaufort Sea, Chukchi Sea, Kaktovik, polar bear movements, polar bears, population estimate, Prudhoe Bay, satellite collars, sea ice, Southern Beaufort, tracking polar bears, USGS