USGS biologists were clearly busy this spring putting more satellite radio collars and glue-on tags on Southern Beaufort Sea polar bears but there’s some surprising information in their April 2015 tracking map about current sea ice conditions.
From the 2013-2014 issue of “Polar Bear News” (USFWS).
What’s interesting is that the sea ice maps they use show less dark spots that might be open water this year than were present last year in late April. Oddly, this phenomenon has one prominent biologist worried about “challenging” polar bear habitat developing this year – without mentioning last year at all.
The USGS track map for April 2015 is copied below.1
Posted in Life History, Sea ice habitat
Tagged Beaufort Sea, Chukchi Sea, Eastern Beaufort, habitat, ice maps, melt ponds, polar bear movements, polar bears, satellite collars, satellite images, sea ice, Southern Beaufort, tracking polar bears, USGS
The trouble is, sea ice researchers and atmospheric scientists have not drawn that conclusion, despite what a new paper by Pilfold and colleagues imply. It shows just what lengths desperate IUCN Polar Bear Specialist Group (PBSG) biologists will go to in order to link the recent decline of Southern Beaufort bear numbers to global warming while ignoring similar past declines.
Posted in Advocacy, Life History, Sea ice habitat
Tagged Beaufort Sea, climate change, Derocher, Eastern Beaufort, extinction, feeding, future, global warming, IUCN Polar Bear Specialist Group, models, Pilfold, polar bear, population, predation, predictions, Red list, ringed seals, Southern Beaufort, Stirling, thick spring ice, threatened
This week, Arctic sea ice in Canada, where 2/3 of the world’s polar bears live, had more sea ice than was present in the early 1970s. Globally, the ice is spitting-distance close to the 1981-2010 average calculated by the NSIDC for this date – which means lots of winter/spring hunting habitat for polar bears.
This is the peak of the polar bear birthing season (both in the wild and in zoos.) Newborns will be snug in maternity dens built by their mothers onshore or on the sea ice; the rest of the population will be out on the ice.
Regional ice charts going back to the late 1960s and early 1970s for this week show even more surprises — have a look.
Posted in Sea ice habitat
Tagged baffin bay, Davis Strait, Eastern Beaufort, Eastern Canada, Hudson Bay, ice extent, polar bear, polar bear habitat, polar bears in winter, sea ice, Southern Beaufort, Western Arctic
Poor polar bear researchers: there are few full time jobs worldwide and research is underfunded.
This is not my opinion but the facts according to Andrew Derocher and Ian Stirling (2011) — see Fig. 1 and 2 below. I do not dispute them.
Figure 1. The distribution of full-time polar bear researchers worldwide. From Derocher and Stirling 2011, invited speaker presentation to the 2011 Polar Bear Meeting in Nunavut, Oct 24-26.
Since Derocher and Stirling have raised the issue, I contend it’s perfectly valid to ask: are polar bear biologists who proclaim their heartfelt fear for the future of polar bears at every opportunity behaving as advocates for polar bears or protecting their own careers?
Posted in Advocacy, Conservation Status
Tagged 2011 polar bear meeting Nunavut, Circumpolar Action Plan for Polar Bear Conservation, conflict of interest, conservation, COSEWIC, Derocher, Eastern Beaufort, expert testimony, government jobs, grant funding, helicopter survey, jobs, oil money, polar bear research, Southern Beaufort, Stirling, western hudson bay
Here’s the ground-truth follow-up to my suggestion of what polar bear habitat would likely look like 6 weeks after the minimum extent was reached this year – which was looking then like it would mirror 2009.
You’ll find my discussion, posted on September 22, here. At that point (September 13), ice extent was 5.1 million square kilometers; now it is 9.1 million square kilometers (Fig.1).
Have a look at the maps below: Fig. 2 to see how ice extent at October 31st compares to ice extent at the end of October 2009, and Fig. 3 to see what ice concentrations looked like in the Canadian Arctic.
Posted in Life History, Sea ice habitat
Tagged Beaufort, Canadian Ice Service, Chukchi, Eastern Beaufort, Ferguson, grey-white ice, Hudson Bay, polar bear, sea ice extent, summer ice minimum, young ice
Here is the follow-up to my post on the July track map for 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 track map for September was posted on the USGS website on October 17 (delayed due to the US government shutdown) and is copied here below (Figure 1). The ice rebounded during the second half of the month (after the annual minimum was reached on September 13). The ten bears from July were down to eight – their collars might have stopped working or fallen off (most likely), they might have left the area entirely (also possible) or they might have died (the researchers don’t say which).
Figure 1. Original caption: “Movements of 8 satellite-tagged polar bears for the month of September, 2013. Polar bears were tagged in 2013 on the spring-time sea ice of the southern Beaufort Sea. All 8 of these bears have satellite collar transmitters [i.e., all are females]. Polar bear satellite telemetry data are shown with Ice Analysis charts from 26 August, 2013. Ice Analysis charts are made available by the National Ice Center. The land cover is made available by Natural Earth. Click on the above image to enlarge.” [Note that the dots with the polar bear icons are the end points (end September), while the other end of the string is their position in early September, indicating that the ice is now moving towards the shore. The pink dot present in August is almost entirely obscured by the purple dot, which is overlapping the yellow dot on shore in Alaska; also, the light brown dot is on Banks Island, far right.]
It appears that of the eight polar bears still being followed by USGS researchers in September, four are on shore and four are still on the ice.
Only time will tell if the four females on shore are pregnant and preparing maternity dens for the winter, but this seems the likely reason they are not on the ice with the others.
One very interesting point worth noting:
the one bear (light brown) captured onshore in the Southern Beaufort
subpopulation region in the spring of 2013
, has moved into the Northern Beaufort
subpopulation region, on Banks Island (see map here
), and may be denning there. This inter-subpopulation movement is relatively uncommon.
The map for July 2013 is below, for comparison: Continue reading
Posted in Life History, Sea ice habitat
Tagged Beaufort Sea, denning females, Eastern Beaufort, females with radio collars, habitat, Northern Beaufort, polar bears, sea ice extent, Southern Beaufort, summer ice minimum, summer sea ice, tracking polar bears, tracking polar bears by satellite, USGS
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
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
Now that we have a plausible explanation (previous post here) for why shorefast ice in the Eastern Beaufort got too thick for ringed seals every ten years or so, it’s time to talk about the effect that this recurring sea ice phenomenon might have had on polar bear population numbers.
We know from the reports of polar bear biologists that without fat young seals to eat in the spring, some bears in those thick-ice springs came close to starving and many mothers lost all or most of their cubs (Amstrup et al. 2006; Stirling 2002; Stirling and Lunn 1997; Stirling et al. 1980; Stirling et al. 2008). This presumably had some impact on population numbers – the question is: how bad was it?
None of the reports on the effects of the thick ice have given us any indication of how many polar bears might have died or lost their cubs. However, Ian Stirling and colleagues (Stirling et al. 2011) recently published a paper on the Northern Beaufort subpopulation that looked, at first glance, to have done just that.
You have to keep in mind that the geographic area in question – the Eastern Beaufort – is not an official polar bear subpopulation region – at least, not any more. As Fig. 1 below shows, the Eastern Beaufort was once its own, strictly Canadian region (or at least, a strictly Canadian research region) see previous post here), but management is now shared between two subpopulations and managed by two governments (Canada and the USA). About half of the bears of the “Eastern Beaufort” reside in the ‘Northern Beaufort’ subpopulation and the other half live in the ‘Southern Beaufort’ subpopulation.
Figure 1. Re-jigging of polar bear subpopulations now splits what used to be
an entirely a Canadian research segment, called the “Eastern Beaufort” (map on the left, from Stirling and Lunn 1997), into management regions called “Southern Beaufort” (shared with the USA) and “Northern Beaufort,” with the Canada-USA border at 141 W (map on the right, from Stirling et al. 2011, Fig. 1). Labels added. Most of the polar bears sampled for the Stirling et al. paper were captured along the west and south coasts of Banks Island, although a few were captured in M’Clure Strait and in Amundsen Gulf.
Despite the changing boundaries, ringed seals and polar bears in the Eastern Beaufort have been the focus of research since the early 1970s. In part, this is because the region has been targeted for oil exploration and studies on both species have been part of the associated ecological impact assessments (Stirling et al. 1993).
Getting back to the point, did Stirling et al. 2011 find fluctuations in polar bear numbers in the Northern Beaufort that might reflect the periodic bouts of thick spring ice in the Eastern Beaufort? Unfortunately, no — the data lack necessary precision. You’ll see why, I think, from the summary below. Continue reading
Posted in Population, Sea ice habitat
Tagged Amundsen Gulf, Banks Island, Eastern Beaufort, Ian Stirling, ice thickness, Northern Beaufort, population estimates, population numbers, Southern Beaufort, 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