Tag Archives: summer

New paper updates lack of trend in W Hudson Bay breakup/freeze-up dates to 2015

A newly-published paper shows that there has been no trend in the time Western Hudson Bay polar bears spent onshore between 2001-2015 due to sea ice conditions at breakup or freeze-up (previously available to 2010 only), despite the marked decline of global sea ice since 2007.

castro-de-la-guardia-et-al-derocher-2017-fig-3-no-caption

Figure 3 from Castro de la Guardia (2017) showing freeze-up and breakup dates and ice-free days 1979-2015 for Western Hudson Bay. Figure with caption is copied below, with explanation of symbols.

Previously, a 2007 paper by Eric Regehr and colleagues for WHB bears up to 2004, which was used to support the US bid to list polar bears as ‘threatened’ with extinction, concluded that between 1984 and 2003, bears were spending 3 weeks long onshore than they did in the 1980s.

The big news from Castro de la Guardia (2017) is that polar bears spent longer onshore from 1979-2015 by … 3 weeks. That is, no change from the situation in 2004. Wow!

Note the population size of the entire WHB subpopulation has also not declined since 2004 and is currently estimated at about 1030, based on a 2011 aerial survey (Stapleton et al. 2014).

Thanks to Andrew Derocher for the heads-up tweet.

From the abstract (my bold):

We found that the ice-free period in this region lengthened by 3 ± 0.8 wk over the period 1979−2015. Polar bears migrated onshore 2 wk earlier and offshore 1 wk later in the period 2005−2015 than in 1980−1989.

Here is the region in question, illustrated by Fig. 1 from the paper:

castro-de-la-guardia-et-al-derocher-2017-fig-1a-locationThe significant information contained in this paper is breakup and freeze-up dates and length of the ice-free period data for 2010-2015, which has been unavailable until now. More excerpts and comments below, including Figure 3 with its caption. Continue reading

Arctic sea ice grows & Churchill polar bears into their 4th month of fasting

A quiet year for problems in the polar bear capital of the world (Churchill, Manitoba) so far – despite this year tying for the second-lowest minimum since 1979 – and the ice is growing fast. In fact, Arctic ice growth in the second half of September was rapid and there is now more ice than there was at this date in 2007 and 2012 (when polar bears in those regions considered most at risk did not die off in droves).

masie_all_zoom_4km-2016-oct-12

Pessimistic polar bear specialists are wrong  – polar bears are much more resilient to low sea ice levels in summer than they assume: their own data from low summer ice years proves it.  If you’ll recall from my previous post, polar bears seem to have barely survived the extensive sea ice coverage during the Last Glacial Maximum – in other words, too much ice (even over the short term) is their biggest threat. Polar bear numbers, as confirmed by the latest estimates in the 2015 IUCN Red List assessment, are higher now than they have been since the 1960s, despite almost 10 years of summer sea ice minimums below 5.0 mk2.

Churchill Polar Bear Alert reports and Arctic sea ice comparisons at this date, in detail below.

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Polar bear onshore in Tuktoyaktuk got so close to kids they heard it breathing

A report from the CBC this morning (with video) of a large polar bear wandering about the village of Tuktoyaktuk on the (Canadian) shore of the Eastern Beaufort Sea on Thursday (29 September) that got very close to a group of children playing outside. Fortunately, no one was hurt.

tuk-polar-bear-sighting-sept-29_cbc-oct-1-2016-headline

That this was a rare event is evident in the awe and excitement in the voices of the residents as someone recorded the movements of the bear through town (picture quality is not the best, but clear enough).

As I’ve said before, with more bears we can expect more interactions with people and more sightings like this that haven’t happened in decades. Map and quotes below.
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Polar bears seldom catch seals they stalk in summer – it’s why they fast

This short BBC video shows why polar bears are so often unsuccessful in their summer hunts – adult bearded seals are the species most often available on the ice. These seals are not only predator-savvy but there are lots of escape routes in the melting ice, and this has always been so.

“Hungry polar bear surprises a seal – The Hunt: Episode 2 Preview – BBC One”

Melting ice in summer is not a new phenomenon (e.g. NASA photo below from mid-July 2016) – Thomas Grenfell and Gary Maykut described the process of melt pond development back in the 1970s:

“Melt ponds reach the maximum extent shortly after the disappearance of the snow, when they may cover upwards of 50% of the ice.”

sea-ice_melt-ponds_nasa-taken-13july2016_sm

Melting summer ice has always made it challenging for polar bears to catch seals, as this quote from Ian Stirling (1974) show, based on his work in the Central Canadian Arctic in the summer of 1973 (July and August):

There is a great abundance of natural holes in the ice during summer, anyone of which a seal could surface through.

This is still true in areas like the Southern Beaufort Sea today (e.g. Whiteman et al. 2015): the ice melts and in some areas, disappears completely in summer.

It’s why polar bears – unlike other species of bears in summer – depend on their stored fat to see them through until the ice reforms in the fall.

The meme “If there’s no ice, there’s no ice bear” is political-style rhetoric, not science.

[When polar bear scientists say “sea ice” or “ice” – they mean summer sea ice. Sea ice in winter and spring are not predicted to decline by 2100 to any appreciable degree and that has been true since sea ice predictions began]

Polar bears in Hudson Bay and Davis Strait routinely go 4-5 months without sea ice in the summer and have done since studies on them began. Yet, all of the polar bear subpopulations in Hudson Bay and Davis Strait are stable or increasing.

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Tracking polar bears in the Beaufort Sea during August 2016

Only three females with collars are still being tracked by USGS researchers in the Beaufort Sea and all of them spent August 2016 on the sea ice in the eastern portion, off the coast of Banks Island.

tranquilized_pb570_s-beaufort-march-2014_usgs

Meanwhile, as Arctic sea ice nears the annual low, NSIDC predicts that 2016 will likely not set a new record but may bottom-out below 2007 (the second-lowest since 1979). The impact of low September sea ice on polar bear health and survival, based on recent research reports, will be the topic of an upcoming post.
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Most polar bears easily deterred this time of year, lucky Labrador boaters discover

A polar bear female accompanied by a cub recently attempted to board a small sailboat anchored in a remote harbour off central Labrador – giving the two American boaters below deck a mighty big surprise.

Labrador polar bear encounter Torngat boat_CBC 30 Aug 2016

‘He said ‘it’s a bear, it’s right on the boat, make some noise.'” – Nancy Zydler

The encounter occurred south of the same national park where a much-publicized attack occurred in July 2013 (see previous posts here and here) but had a happier ending. See more below from a CBC report released this morning (based on a radio interview) and some ecological context for the sighting not mentioned by the reporter.
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Sea ice habitat Canada update for 23 July 2016 vs. 2014 & the start of bear problems

Sea ice breakup is always a little bit different year to year but since I have the maps archived, take a look at the differences and similarities at this date for this year compared to 2014…

Sea ice extent Canada 2016 July 23_CIS

Sea ice extent Canada 2014 July 23 CIS

Is there evidence that any polar bears – say Western Hudson Bay bears, for example – were negatively affected by sea ice levels in 2014? Not that I’ve heard. In fact, quite the opposite.

Polar bear guide and blogger Kelsey Eliasson, writing from Churchill, Manitoba, had this to say about the condition of bears and freeze-up that year (16 Nov. 2014):

“With these families appearing [heading out to the ice], it really sums up at just what a productive season this has been for the western Hudson Bay population. Any guide who knows their stuff will tell you this was a banner year for cubs, one we haven’t seen in a long time.”

Meanwhile, bears are starting to come ashore and cause a bit of grief:

Southern Hudson Bay (two days ago): “Polar bear shot after wandering through Kashechewan” [see map below for location: the bear shot was a cub that appears to have been separated from its mother and sibling, who were spotted several km away not causing any trouble]

Iqaliut, Baffin Island (this morning): “Polar bear rips 6 tents pitched in Iqaluit park”

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