There’s almost more blue in the Canadian Ice Service “departure from normal” charts for this week than red, which means more sea ice than usual, especially in the eastern half of the bay and northern Labrador. Eventually, the melting ice will force polar bears ashore where they will fast for 4-5 months, living off the fat they’ve put on over the spring feeding season.
Last week’s media coverage made me realize that James Hansen’s testimony to a US Senate committee in 1988 provided well-timed answer to a vexatious problem facing polar bear biologist Ian Stirling. Thirty years ago, Stirling was struggling to understand why polar bear productivity in Western Hudson Bay had dropped. He was ripe for the suggestion from Hansen (and his follow-up paper) that human-caused global warming could be the explanation. An interview with Stirling and colleague Andrew Derocher published in 2016 helps connect the dots.
Many bears were in poor condition in the fall of 1983 (Calvert et al. 1986:19, 24; Ramsay and Stirling 1988). In general, the 1980s saw weights of bears decline and cub mortality increase, with a marked increase in the loss of whole litters over what had been documented in the 1960s and 1970s (Derocher and Stirling 1992, 1995).
Until Hansen and climate change came along, density-dependent effects (such as the number of bears out-pacing food supply) were seen as the most likely explanation. But sea ice decline blamed on human-caused global warming was suddenly a new possibility that Stirling soon embraced (Stirling and Derocher 1993). By the late 1990s, sea ice coverage on Hudson Bay had indeed declined but the correlation with polar bear productivity produced a weak trend that was not statistically significant (Stirling et al. 1999).
The 1999 Stirling paper did not provide scientific evidence to explain the 1980s decline in productivity as much as it presented a novel scapegoat to blame when a more plausible explanation could not be made.
Bottom line: Global warming could not have been the proximate cause of the productivity changes in WH polar bears documented during the 1980s but Stirling spent the next two and a half decades vigorously pushing climate change as the cause of all polar bear ills. Continue reading
Posted in Conservation Status, Life History, Population, Sea ice habitat
Tagged body condition, climate change, decline, density-dependent response, global warming, Hansen, natality, polar bear, productivity, sea ice, Stirling, survival
Despite pronouncements from one polar bear specialist that “ice in Hudson Bay is in rapid retreat” a look back in time shows that there is more thick first year ice over the Bay this year for the week of the summer solstice than there was in 2004 – and much less open water than 1998.
Below, 2018, June 18 (the week of the summer solstice):
Compare the above to the same week coverage chart for 2004, below:
Ice coverage for some other recent years are shown below compared to 1998, the year the ice breakup pattern on Hudson Bay changed. Speed and melt sequences vary according to the amount of thick first year ice present, discussed previously here.
PS. If you’re wearing white today, flaunt it! Tell your friends and colleagues that you’re celebrating the success of polar bears despite such low summer sea ice since 2007 that 2/3 of them were predicted to disappear.
Posted in Sea ice habitat
Tagged breakup, decline, freeze-up, Hudson Bay, melt, observations, polar bear, retreat, sea ice, solstice, thick first year ice
Wednesday 21 June is the longest day of the year: wear something white tomorrow to acknowledge and celebrate the success of polar bears despite such low summer sea ice since 2007 that 2/3 of them were predicted to disappear.
White tie, white shirt, white socks work too. Keep cool and signal to the world that you love outstanding survivors of climate change, fat though they may be.
Read here and here.
Global sea ice extent at 19 June 2018, well past the end of the intensive spring feeding period for polar bears:
Last week, the Norwegian Polar Institute updated their online data collected for the Svalbard area to include 2017 and 2018 — fall sea ice data and spring polar bear data. Older data for comparison go back to 1993 for polar bears and 1979 for sea ice, showing little to no impact of the reduced ice present since 2016 in late spring through fall.
Here’s what the introduction says, in part [my bold]:
“…The polar bear habitat is changing rapidly, and the Polar Basin could be ice-free in summer within a few years. Gaining access to preferred denning areas and their favourite prey, ringed seals, depends on good sea ice conditions at the right time and place. The population probably increased considerably during the years after hunting was banned in 1973, and new knowledge indicates that the population hasn’t been reduced the last 10-15 years, in spite of a large reduction in available sea ice in the same period.”
See Aars et al. 2017 for details on the 2015 Svalbard polar bear population count, keeping in mind that the subpopulation region is called “Barents Sea” for a reason: only a few hundred individuals currently stick close to Svalbard year round while most Barents Sea bears inhabit the pack ice around Franz Josef Land to the east (Aars et al. 2009; Crockford 2017, 2018).
Posted in Advocacy, Conservation Status, Sea ice habitat
Tagged Barents Sea, body condition, decline, denning, Derocher, Franz Josef Land, litter size, mothers with cubs, polar bear, population, sea ice, Svalbard
Just out (6 June 2018) — new population assessment and status maps of the 19 polar bear subpopulations according to Environment Canada. Contrary to the map presented at the Range State meeting in February 2018 (pdf here), these maps show Western Hudson Bay and Southern Hudson Bay (along with the Southern Beaufort) as “likely declined.” A new category has been added for the Barents Sea: it’s considered “data deficient/uncertain,” but a population estimate of 2,001-3,000 has been provided.
No press release or other notice regarding the availability of these new maps was issued, as far as I know: I came across them by accident while looking for something else.
Global map above, more below, including a comparative map that shows 2010, 2014, and 2018 together. I will update the two recent posts of mine (here and here) that used the February Range State map with the information that more recently revised maps are now available.
Polar bear season for St. Lunaire-Griquet Newfoundland ran from 6 March to 10 June this year — three long months when polar bears came to visit the community during the season when bears are usually occupied with feeding on young seals and mating.
Below is a map of the region: St. Lunaire-Griquet is at the tip of the Northern Peninsula of Newfoundland, just north of St. Anthony (where some of the action in my polar bear attack thriller, EATEN, takes place):
As of yesterday (June 10), when the last sighting of a fat and healthy polar bear took place, there was still quite a mass of thick first year ice (>1.2 m thick) off the northern peninsula of Newfoundland, amongst a field of icebergs:
The first sighting in the area this year was back in early March, which I blogged about here. Fortunately, the Davis Strait bears that occupy the East Coast pack ice are usually well feed at this time of year and seldom pose a serious threat to humans: the fact that visitors ashore are often easily pursuaded to leave (or do so on their own) suggests they are more curious than hungry.
Posted in Life History, Polar bear attacks, Sea ice habitat
Tagged ashore, East Coast, Eaten, harp seal, icebergs, Newfoundland, polar bear, sea ice, sightings, St. Anthony