Sea ice development over Hudson Bay, Hudson Strait, and Davis Strait has been rather unusual this year but what that might mean for polar bears over the coming winter and spring is hard to tell.
Note: The Canadian Ice Service seems to be in the process of updating its sea ice page and graphing features that used to be available weekly on Thursday have not been available until the following week. This means the most recent graphs available are for the week of 11 December (see below).
Posted in Sea ice habitat
Tagged 1992, Davis Strait, El Nino, Foxe Basin, freeze-up, heavy sea ice, Hudson Bay, Hudson Strait, polar bear, polar bear facts, sea ice, western hudson bay
“Blizzards, we had fog — we had to sleep in the helicopter, on the sea ice one night, because we couldn’t fly anywhere,” Markus Dyck, senior polar bear biologist with the GN, told Nunatsiaq News Sept. 5.”
Fog was the theme of polar bear research this summer in Queen Maud Gulf, otherwise known as the M’Clintock Channel polar bear subpopulation region.
The ice has been heavy in that region as well, according to a the National Snow and Ice Data Center (NSIDC) and reported yesterday in another story (“Heavy pack ice in NW Passage ice creates tough conditions this year: Pack ice clogs Queen Maud Gulf“).
For maps showing where M’Clintock Channel and Queen Maud Gulf actually are, see the maps — and more quotes — below.
Posted in Population, Sea ice habitat
Tagged biopsy dart, heavy sea ice, helicopter survey, M'Clintock Channel, Markus Dyck, Northwest Passage, NSIDC, polar bear, population estimate, population survey, Queen Maud Gulf, tagging
Remember Ian Stirling’s claim that late freeze up in Western Hudson Bay in 2009 was forcing polar bears to resort to cannibalism (here and here), with gut-wrenching images and video provided for the media? Or Steve Amstrup’s claim for a similar phenomenon in the Southern Beaufort in 2004?
I pointed out that Stirling’s claim was way overblown and that Amstrup’s incidents were almost certainly the result of heavy ice in the spring (not low ice in summer), similar to the heavy ice conditions and polar bear starvation documented in the same region back in 1974-1976.
It turns out that the heavy ice conditions documented in the Eastern Beaufort in the mid-1970s had much broader effects on polar bears and ringed seals than has been appreciated.
Posted in Cannibalism, Conservation Status, Sea ice habitat
Tagged Beaufort Sea, Bering Sea, body condition, cannibalism, Chukchi Sea, heavy sea ice, Ian Stirling, Jack Lentfer, John Burns, mortality events, polar bear, Polar Bear Specialist Group, ringed seals, spring sea ice, starving polar bears, Steven Amstrup, summer ice minimum
One aspect of the recently published study on Chukchi Sea polar bears (Rode et al.2014 [now in print]
2013; see here and here) has not been stressed enough: their finding that the differences in overall condition between bears in the Chukchi and Southern Beaufort Seas came down to disparities in spring feeding opportunities and therefore, the condition of spring sea ice.
The fact that spring — not summer — is the most critical period for polar bears is something I’ve pointed out before (see here and here, for example) but it’s worth repeating at this time of year, when all eyes are on the annual ice minimum. It is often treated as a given that the decline in extent of summer sea ice in the Arctic since 1979 has been detrimental to polar bears. However, this is an assumption that we can now say is not supported by scientific evidence (see summary of that evidence here).
The results published by Rode et al. (2014
2013) not only add further support to the conclusion that declines in summer sea ice have not harmed polar bears, but should put the matter to rest – unless new evidence to the contrary is produced.
Chukchi bears, the report tells us, had more food available in the spring than Southern Beaufort bears (see map below) and this was the primary reason that bears were doing very well in the Chukchi and not quite as well in the Southern Beaufort. And because the polar bears for this study were captured and measured in mid-March to early May, from 2008 to 2011, they reflect spring-time conditions for 2008-2011 as well as year-round conditions from 2007 through 2010.
This means that the annual low ice extent for 2007 (record-breaking at the time), in the fall before this study began, had no discernible negative effect on either Chukchi or Southern Beaufort polar bears – and neither did similarly low annual minimums in two of the three remaining years of the study (Fig 1).
Posted in Conservation Status, Life History, Sea ice habitat
Tagged annual summer minimum, arctic sea ice, Beaufort Sea, body condition, Cherry, Chukchi, declining sea ice, Eastern Beaufort, good news, heavy sea ice, Hudson Bay, ice-free Arctic, litter size, loss of summer ice, Pilfold, polar bear, record low, Regehr, ringed seals, Rode, sea ice extent, Southern Beaufort, Stirling, summer ice minimum, summer sea ice, thick spring ice
The polar bear biologists and professional activists of the IUCN Polar Bear Specialist Group (PBSG) continue to insist that since 1979 increasingly smaller amounts of Arctic sea ice left at the end of summer (the September ice minimum) have already caused harm to polar bears. They contend that global warming due to CO2 from fossil fuels (“climate warming” in their lexicon) is the cause of this decline in summer ice.
In a recent (2012) paper published in the journal Global Change Biology (“Effects of climate warming on polar bears: a review of the evidence”), long-time Canadian PBSG members Ian Stirling and Andrew Derocher (both of University of Alberta) summarized their position this way:
“Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze-up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long-term survival”
I’ve spent the last year examining their evidence of on-going harm, but in addition, I’ve looked at the evidence (much of it not mentioned in the Stirling and Derocher paper1) that polar bears have either not been harmed by less sea ice in summer or have thrived in spite of it.
This is a summary of my findings. I’ve provided links to my original essays on individual topics, which are fully referenced and illustrated. You are encouraged to consult them for complete details. This synopsis (pdf with links preserved, updated; pdf with links as footnotes, updated) complements and updates a previous summary, “Ten good reasons not to worry about polar bears” (pdf with links preserved; pdf with a foreword by Dr. Matt Ridley, with links as footnotes).
Update 8 September 2013: to include links to my post on the recently published Chukchi population report; updated pdfs have been added above.
Update 22 January 2014: added figure comparing March vs. September sea ice extent using the same scale, from NOAA’s “2014 Arctic Report Card,” discussed here.
Posted in Conservation Status, Population, Sea ice habitat, Summary
Tagged Arctic, Barents Sea, Beaufort Sea, body condition, breakup dates, cannibalism, Chukchi, climate change, climate warming, Davis Strait, death spiral, Derocher, global warming, harm to polar bears, heavy sea ice, Hudson Bay, hybridization, ice-free, negative effects, polar bear, polar bear numbers increasing, Polar Bear Specialist Group, Polar Bears International, prolonged ice-free season, ringed seals, sea ice, sea ice decline, September ice minimum, Stirling, summary, summer ice minimum, victim of climate change
We know that thick-ice springs occurred in 1974, 1975, 1986, 1992, 2004, and 2005 in the former ‘Eastern Beaufort’ – now the southern portion of the ‘Northern Beaufort’ and the eastern portion of the ‘Southern Beaufort.’ We know that these severe spring ice conditions negatively impacted both polar bears and ringed seals in this region every decade since the 1960s because the effects have been documented by numerous studies conducted in April through May for polar bears (Amstrup et al. 2006; Cherry et al. 2009; Pilfold et al. 2012; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1980; Stirling et al. 1993; Stirling et al. 2008) and in June and July for ringed seals (Harwood et al. 2012; Smith 1987), see previous posts here, here, and here.
For example, even though Ian Stirling and colleagues argued in their 2008 paper that the thick spring ice conditions in 2004, 2005 and 2006 (but not those in previous decades) were caused by storms initiated or intensified by greater amounts of open water in previous summers, they did not deny that the thick-ice springs occurred. They stated quite clearly that:
“The 1960s, 1970s, and 1980s each experienced a two- to three-year decline in seal productivity in the eastern Beaufort Sea and Amundsen Gulf, associated with heavy ice conditions, around mid-decade. Each was followed by a decline in polar bear reproduction and condition, after which both seal and bear populations recovered (Smith, 1987; Harwood et al., 2000; Stirling, 2002). The beginning of each of those three periods was associated with heavy ice conditions through the winter before the reproductive decline of the seals, followed by a late spring breakup.” [my bold]
So, I have to say, I was shocked but not surprised to find that in the more recent scientific literature, the phenomenon of thick-ice springs every decade in Southern and Northern Beaufort has been deliberately ‘disappeared.’
Not surprised because I suspected it had happened — this issue was a feature of the Stirling and Derocher (2012) paper from late last year which was the topic of my very first blog post, “Cooling the polar bear spin.”
However, I think it is important to document how the transmogrification of sea ice effects on polar bears was managed in the scientific literature so that everyone can see exactly what has been done. In a truly astonishing move for what is supposed to be a field of science, thick-ice springs have been effectively replaced by an open-water red herring as the scourge of Southern Beaufort polar bears.
Posted in Advocacy, Conservation Status, Sea ice habitat
Tagged Beaufort Sea, Cherry, Derocher, Eastern Beaufort, heavy sea ice, Northern Beaufort, open water, Regehr, ringed seals, Rode, Southern Beaufort, status, Stirling, summer ice minimum, thick spring ice
I’ve written before about the incidents of starving polar bears in the eastern portion of the Southern Beaufort Sea (here, here, and here). For two or three years every decade since the 1960s, shorefast ice in the Eastern Beaufort (Fig. 1) has become too thick and compressed in the spring for ringed seals to maintain their breathing holes, so most or all of them presumably go elsewhere — as seals did in Greenland when ice got too thick there (Vibe 1965). With few or no seal pups born during March and April in thick ice years, some bears had a hard time finding enough food: starving bears and dying cubs were the result.
Figure 1. ‘Eastern Beaufort’ (yellow square) polar bear study region.
The communities of Tuktoyatuk (locally known as ‘Tuk’), and Sachs Harbour on southern Banks Island have been used as base camps for polar bear research because they are accessible by plane via the larger community of Inuvik.
The light blue portions along western Banks Island and the Eastern Beaufort/Yukon mainland coast indicate shallow continental shelf areas (20 km wide in places) where extensive shorefast ice develops every winter.
Main map from Beaufort Sea Partnership, inset map from Wikipedia.
I’ve been trying to get my head around why this would happen in the Eastern Beaufort. Once or twice – maybe – but several times every decade? What on earth drives such a process?
So, I did some reading (actually, quite a lot of reading) and have what appears to be at least a partial answer.
All indications are that the occasional development of exceptionally thick spring ice in the Eastern Beaufort is the result of an entirely natural, cyclical phenomenon. However, some polar bear biologists are attempting to blame the latest episode (but not earlier ones) on increased amounts of open water in the Chukchi Sea during fall of the early 2000s. That doesn’t seem a plausible explanation to me, given the history of the sea ice in this region. Have a look.
Figure 2. Beaufort sea pressure ridges, spring 1949. Courtesy Wikipedia (from NOAA’s “At the ends of the Earth” image collection #corp1014).
Posted in Life History, Sea ice habitat
Tagged Arctic storms, Banks Island, Beaufort Gyre, Eastern Beaufort, Harwood, heavy sea ice, ice thickness, Melling, multiyear ice, pressure ridges, Ramseier, ringed seals, shorefast ice, spring ice conditions, Stirling, Vibe