No early breakup of Hudson Bay sea ice again this year: there is still extensive thick first year ice over most of Hudson Bay and all female polar bears fitted with tracking collars in Western Hudson Bay are still on the ice:
W Hudson Bay polar bears still out on the ice that’s packed together by winds. AE Derocher, 12 June 2020
Breakup of Hudson Bay sea ice as it relates to polar bear movement to land has been about the same since 1999 (about 2 weeks earlier than in the 1980s) and this year is shaping up to be no different: there is still no declining trend in date of sea ice breakup in Western Hudson Bay despite repeated predictions of imminent doom. An especially ‘early’ breakup year would have bears ashore before 15 June. Last year (2019) the first WH bear onshore was caught on film 5 July and problem bears were not recorded onshore in Churchill until the 2nd week of July.
Posted in Conservation Status, Life History, Sea ice habitat
Tagged breakup dates, declining population, early breakup, Hudson Bay, polar bear, sea ice, threatened, trends, western hudson bay
There is still a huge swath of highly concentrated thick first year ice (>1.2m) over most of Hudson Bay this week (19 June 2017) and even in the NW quadrant (the closest proxy we have for Western Hudson Bay), the weekly graph shows levels are greater than 2016, when WHB bears came off the ice in good condition about mid-July. All of which indicates 2017 won’t be an early sea ice breakup year for WHB polar bears.
There is thick first year ice (>1.2m, dark green) in patches along the west coast in the north and south. Thick first year ice also extends into Hudson Strait and Baffin Bay, with some medium first year ice (0.7-1.2m thick, bright green) along the central and southern coasts of WHB. Note the red triangles incorporated into the thick ice of Hudson Strait in the chart above: those are icebergs from Greenland and/or Baffin Island glaciers. A similar phenomenon has been noted this year off northern Newfoundland, where very thick glacier ice became mixed with thick first year pack ice and were compacted against the shore by storm winds to create patches of sea ice 5-8 m thick.
Compare the above to what the ice looked like last year at this time (2016 20 June, below). There is more open water in the east this year (where few WHB bears would likely venture anyway) but less open water around Churchill and Wapusk National Park to the south than there was in 2016:
We won’t know for several more weeks if most WHB bears will come ashore at about the same time as last year (early to mid-July) or whether they will be in as good condition as they were last year (because winter conditions may not have been similar).
But so far, sea ice conditions are not looking as dire as the weekly “departure from normal” chart (below, 19 June 2017) might suggest (all that “less than normal” red and pink, oh no!!):
Posted in Conservation Status, Life History, Sea ice habitat
Tagged breakup, concentration, early breakup, extinction, habitat, ice charts, observations, polar bear, predictions, sea ice, survival, trends
Polar bear population estimates for Western Hudson Bay have recently become contentious because one specialist has been making statements that confuse the issue. As we all wait for the release of the report on the WHB aerial survey of 2016, it’s worth going over the recent history of these counts and what they have revealed.
The official count for bears in WHB (used by the IUCN Polar Bear Specialist Group, the IUCN Red List, and Environment Canada) is 1030, based on an aerial survey of the entire region conducted in 2011 (Stapleton et al. 2014).
Since last year, Andrew Derocher (University of Alberta) has been telling any media pundit who will listen that WHB polar bears have declined from about 1200 bears in the 1980s to only 800 or so bears today (one example here) — a statement that is clearly not true. In recent months, however, whether due to complaints from the public or from his colleagues, he’s qualified that statement by saying it’s the number of bears in the “core” area of WHB that has declined.
But is Derocher’s revised statement a clear scientific interpretation of the facts? Have a look at the details below and see if you come to the same decision I have: that it’s not possible to compare WHB ‘core’ area polar bear population estimates over time.
Posted in Life History, Population, Sea ice habitat
Tagged breakup dates, Churchill, counting polar bears, Derocher, early breakup, estimates, Ontario, polar bear, population numbers, Wapusk National Park, western hudson bay
Breakup for Western Hudson Bay (WHB) is looking to be later than usual this year, given that the average breakup date since 1991 has been July 1 (using a 30% threshold) – only a few days from now – and the ice in WHB is nowhere near 50% coverage, let alone 30%.
Note that few WHB bears come off the ice around Churchill – most come ashore along the southwest coast of Hudson Bay (almost into SHB) and make their way north over the course of the summer to meet the ice as it reforms in the fall north around Churchill – that’s why it’s called a “migration.”
There’s still a lot of ice left in Hudson Bay, as the Canadian Ice Service map for 29 June 2016 (below) shows:
It seems to me that breakup for WHB this year is looking rather like 2014, which was something like a week later than the average since 1991, but time will tell. See below for comparison to 2009 (a late breakup year), 2015, and 2013 (lots of variability!), as well as a discussion of when bears come ashore in relation to this sea ice breakup benchmark.
Posted in Life History, Sea ice habitat
Tagged 30 percent coverage, breakup, Cherry, Churchill, early breakup, late breakup, onshore, polar bear, sea ice, Southern Hudson Bay, variability, western hudson bay
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
Evolution is not just for the long-term – natural selection also goes on over short time periods. In the case of polar bears, this adaptation is almost certainly critical for its long-term survival.
Hudson Bay female with cub Wapusk National Park, Thorsten Milse, Government of Canada
Not all polar bears are identical — that is the reality that allows natural selection to operate.
I will argue that early breakup years in Western Hudson Bay weed out individual polar bears that do not have the physiological or behavioral characteristics necessary to be useful members of the population – and that this is a good thing for the entire population.
Posted in Evolution, Population, Sea ice habitat
Tagged adaptation, declining sea ice, early breakup, evolution, historical sea ice record, indivdual variation, late freeze-up, natural selection, NSIDC, polar bear, resilience, sea ice minimum, sea ice variability, Stirling, Stroeve, survival, western hudson bay
“Our results suggest that mark–recapture estimates may have been negatively biased due to limited spatial sampling. We observed large numbers of bears summering in southeastern WH, an area not regularly sampled by mark–recapture.” Stapleton et al. 2014.
Polar bear at Wapusk National Park in August 2011. Courtesy Parks Canada.
We’ve seen the results of this 2011 study before, in government report format. But now it’s been revamped, peer-reviewed and published in a respected scientific journal – it actually came out in February, without fanfare, but I’ve only just come across it.
Some excerpts below, with conclusions that should raise some eyebrows.
Posted in Conservation Status, Population, Sea ice habitat
Tagged aerial survey, early breakup, endangered, invalid methods, later-than-average breakup, mark-recapture, polar bear, population estimate, Seth Stapleton, Southern Beaufort, Southern Hudson Bay, threatened, US Fish and Wildlife Service, Wapusk National Park, western hudson bay
In the last few days, ice coverage on Western Hudson Bay finally dropped below the 30% level that now defines ‘breakup’ for polar bears: a few bears near Churchill started to come ashore late last week but most will stay on the ice until the end of July. That means breakup this year was unofficially July 8th, a week later than average (July 1) for the third year in a row.
Don’t’ tell that to the folks at Polar Bears International, though, because they’re busy telling people that the ice-free season for Western Hudson Bay bears is now longer than it was before the 1990s. What they mean is that the overall trend is toward early breakup dates.
But what they don’t admit is that over the last 44 years, breakup was a full two weeks earlier than average for Western Hudson Bay only six times and only three of those early breakups occurred within the last 13 years. See the calculations below and see what you think.
Posted in Sea ice habitat
Tagged average breakup date, breakup, Canadian Ice Service, Churchill, early breakup, ice charts, Kelsey Eliasson, late breakup, Polar Bear Provincial Park, prolonged ice-free season, Seth Cherry, Wapusk National Park, western hudson bay
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