From the end of October to mid-December, there has been a rapid expansion of polar bear habitat.
This month, I’ve constructed two all-in-one images that show the progressive growth of the ice relative to some critical polar bear onshore summer refuge areas and denning territory. I’ve also included a map that compares 2013 to 2009 at 18 December with the average for the 1980s, and one that shows ice thickness.
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Comments Off on Polar bear habitat update, December – still like 2009
Posted in Sea ice habitat
Tagged Canadian Ice Service, dens, ice development, MASIE, onshore, polar bear, polar bear habitat, sea ice extent, sea ice thickness, sea ice volume, winter ice
Freeze-up in the Arctic (~October-November) is important to polar bears because for those animals that have spent the ice-free period on shore (not all do), it marks the end of their summer fast — they can finally resume seal hunting.
Polar bears in the most southern regions, like Southern Hudson Bay, Western Hudson Bay, and Davis Strait (see Fig. 1), routinely experience the longest ice-free period. As these bears all spend the summer on shore, they appreciate a timely return of the ice.
Figure 1. Polar bear subpopulations defined by the IUCN Polar Bear Specialist Group (PBSG), with a few extra labels added. I’ve rotated the original map 90 degrees (right) to make it easier to relate to the ice maps below. WH is Western Hudson Bay; SB is Southern Beaufort. Courtesy PBSG. Click to enlarge.
Southern Hudson Bay bear populations routinely experience an ice-free season that is just as long as it is for Western Hudson Bay bears. However, Southern Hudson Bay polar bears numbers have remained stable over the last 30 years. Some folks insist that Western Hudson Bay bear numbers are shrinking to a worrisome degree, despite indications that the recent decline could be nothing more than a return to sustainable levels after a rapid population increase in the late 20th century (similar to changes documented for the Davis Strait and Barents Sea subpopulations).
Have a look at how sea ice – essential polar bear hunting habitat – has developed within these regions over the last 10 days or so (end of November 2013) and how November 2013 compares to November 1979. The ice maps tell the freeze-up story.
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Comments Off on Polar bear habitat update, end of November 2013
Posted in Sea ice habitat
Tagged Barents Sea, Canadian Ice Service, Davis Strait, Hudson Bay, polar bear habitat, Polar Bear Specialist Group, polar bears, prolonged ice-free season, sea ice extent, Southern Hudson Bay, Svalbard, western hudson bay
What did I tell you, back in mid-September?
Have a look at all the polar bear habit, ten days shy of the end of November!
Figure 1. MASIE sea ice extent for November 18, 2013 (using US National Ice Center data). You have to look closely but there is indeed ice forming around Svalbard (just above the tip of Greenland) and in James Bay (southern Hudson Bay). Click to enlarge. High resolution map here.
Figure 2. Canadian Ice Service map. Ice developing rapidly in northern Hudson Bay, Foxe Basin and Davis Strait (between southern Greenland and Baffin Island), with ice also forming along the shore in James Bay (the southern-most region where polar bears are onshore at the moment). Click to enlarge.
Comments Off on Polar bear habitat virtually everywhere now
Posted in Sea ice habitat
Tagged Canadian Ice Service, Davis Strait, Foxe Basin, James Bay, polar bear habit, polar bears, sea ice extent, sea ice maps, Southern Hudson Bay, Svalbard, western hudson bay
Today I’ll discuss the response by Polar Bears International representative Steven Amstrup to a comment submitted during their recent “webchat” at The Guardian (Wednesday, November 6), which had to do with the fact that polar bears survived warm periods in the geological past, particularly interglacials.
[Here’s a pdf file of all the questions that were answered by PBI staff: PBI webchat Q&A, also available here]
This is the comment (the first portion of #4 on my list), submitted by MarkBLR:
There was a paper in Science magazine last year (link …) indicating that polar bears became a distinct species about 600kya (+/- 300k years).
This means that they have survived at least two (and possibly eight) previous inter-glacials, in particular the Eemian (130kya to 110kya), when temperatures in the Arctic were 5 to 8 degrees Celcius warmer than current temperatures for several thousand years.
Note that their numbers apparently decreased significantly during the Eemian, and slowly increased as temperatures cooled, but “climate change” was not enough on its own to make them extinct. [my bold]
[We can perhaps forgive Mark for not being able to spell “Celsius” correctly, but Amstrup (see below) has no excuse. The paper in Science Mark refers to is Hailer et al. 2012, discussed in a previous post here. Note that the actual question Mark asked is not included here because Amstrup responded to this portion of his comment only]
Amstrup tries to convince Mark and other readers that polar bear resilience through Eemian warming is irrelevant to the issue of future survival, which I’ll demonstrate is not the case at all.
Here is what Amstrup had to say:
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Comments Off on Eemian excuses: the warm was different then, polar bears were fine
Posted in Evolution, Population, Sea ice habitat
Tagged Amstrup, average global temperature, Bering Sea, computer models, Eemian interglacial, effective population size, extinction, Hudson Bay, Miller, MIS 5e, polar bear, Polar Bears International, Sangamonian, sea ice extent, summer ice minimum, threatened
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).
Figure 1. Oct 30 2013 Maisie sea ice extent, 9.1 mkm2. Click to enlarge.
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.
Comments Off on Polar bear habitat update for October 31, 2013
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. “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, on shore in Alaska and the light brown dot is ashore on Banks Island, centre right of the map; two of the bears present in July (see Fig. 2 below) are no longer being tracked - 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.] Click to enlarge](https://i0.wp.com/polarbearscience.com/wp-content/uploads/2013/10/beaufort-tracking-usgs-bear-movements-september-2013.jpg){kind=tracking}
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.]
The map for July 2013 is below, for comparison: Continue reading
Comments Off on Tracking polar bears in the Beaufort Sea: September map
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
According to the National Snow and Ice Data Center (NSIDC, Sept. 20 report), the annual sea ice minimum extent was reached on Sept. 13, 2013.
At 5.10 million square kilometers, this year’s low was a whopping 1.69 million square kilometers above the minimum extent for 2012 (which was the lowest since 1979) and well within two standard deviations of the 1979-2010 average. (Two standard deviations: “Measurements that fall far outside of the two standard deviation range or consistently fall outside that range suggest that something unusual is occurring that can’t be explained by normal processes”).
The minimum extent for 2013 is virtually indistinguishable from the minimum for 2009, which was 5.13 million square kilometers. The ice was distributed a bit differently in 2009 – more in the east and less in the west — than it was this year (see Fig. 1 below).
Figure 1. I used JAXA to plot the date the 2013 minimum was reached (September 13, 5.10 million square kilometers, white) with an overlay (purple) for the same date back in 2009 (September 13, 2009, 5.13 million square kilometers), when that year’s minimum was reached. Areas of overlap are pink.
You’ll know from previous discussions here that the annual minimum reached in late summer has little impact on polar bear health and survival (see excellent summary of the evidence for that here). What matters most to polar bears is the presence of ample ice in spring and early summer (March-June), which is their critical feeding period.
But after the fast that many polar bears endure over the height of the summer, they are eager to get back onto the ice and resume hunting. When in the fall does that become possible?
I wondered what the similarity in extent for 2013 and 2009 might tell us about polar bear habitat development over the next month or so.
In other words, what might polar bears this year expect in the way of sea ice development by say, the end of October? When might they be able to start hunting?
Comments Off on What polar bear habitat could look like in another 5-6 weeks
Posted in Life History, Sea ice habitat
Tagged Baffin Island, Chukchi Sea, Davis Strait, Hudson Bay, Hudson Bay breakup, Hudson Bay freeze-up, hunting platform, JAXA, NSIDC, polar bear habitat, polar bears, sea ice decline, sea ice extent, spring ice, summer ice minimum, Svalbard
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).
Figure 1. Sea ice extent at August 27, 2007 – the lowest extent that year (downloaded September 15, 2013 from IARC-JAXA, Arctic Sea-ice Monitor). At the time, it was the lowest extent recorded since 1979 (2012 broke that record). This (2007) was the fall before the Rode & Regehr study on Chukchi/Southern Beaufort polar bears began (2008-2011). The ice was almost as low in 2008 and 2010, while 2009 was more like 2013.
Comments Off on Record sea ice loss in 2007 had no effect on polar bears, Chukchi study confirms
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
I’ve been in the process of looking at the status of polar bears in the Baffin Bay region, which lies to the north of Davis Strait (Fig. 1), but a related issue caught my attention that I think deserves discussion.
Figure 1. Polar bear subpopulations defined by the Polar Bear Specialist Group (PBSG). Note that Baffin Bay, Davis Strait, Western Hudson Bay and Southern Hudson Bay are all similar in that they become ice-free by early fall (the September minimum) or even before.
Recall that in a recent post on the Beaufort Sea ice extent comparison offered by the National Snow and Ice Data Center (NSIDC) here, I commented:
“What puzzled me was why they featured only the last 7 years when satellite data go back to at least 1979. Is there something in that data they don’t want us to see?”
Something similar struck me about the analysis of sea ice in Baffin Bay and Davis Strait conducted by polar bear researchers Karyn Rode and colleagues (Rode et al. 2012). In their comparison of body condition (relative fatness) of bears in Davis Strait and Baffin Bay (see previous post here), they introduced an entirely new sea ice metric – “mean daily summer sea ice concentration,” defined as the mean of values between May 15 and October 15 each year based on ice charts provided by the Canadian Ice Service.
Why invent a metric that has never been used (as far as I know) for analysis of polar bear health, survival or success?
Why not use breakup dates, as has been done for decades for subpopulations in Hudson Bay (e.g. Cherry et al. 2013), where the ice also disappears in late summer?
Is there something in the ice data for Baffin Bay and Davis Strait that Rode and colleagues don’t want us to see?
Since I had already made a composite of Cryosphere Today ice maps at July 12 for my discussion of the Chukchi/Beaufort NSIDC analysis mentioned above, it was relatively easy to look at what was going on in Baffin Bay and Davis Strait on that date in mid-summer. Keep in mind that ice extent and concentration at July 12 records the state of polar bear habitat prior to the late summer decline in sea ice that occurs every year.
Comments Off on Baffin Bay-Davis Strait ice concentration comparison – why use the “summer mean”?
Posted in Life History, Sea ice habitat
Tagged baffin bay, breakup dates, Cryosphere Today, Davis Strait, Karyn Rode, sea ice concentration, sea ice extent, Seth Cherry, Southern Hudson Bay, summer ice minimum, summer sea ice mean, western hudson bay
The most recent issue of Arctic Sea Ice News provided by the National Snow and Ice Data Center (NSIDC) – the official US keeper of sea ice data – (July 17, 2013) included an interesting graph of sea ice extent in the Chukchi and Beaufort Seas at July 12.
They present the data for 2007 to 2013, compared to the new 30 year average1, and note that the Beaufort Sea had “the most extensive ice cover seen there in the last seven summers.” It is also clear from their graph that the 2013 extent was virtually identical to the average in both regions (Fig. 1).
Figure 1. Graph of sea ice extent at July 12 each year from 2007 to 2013 from the National Snow and Ice Data Center, NSIDC. “Climatology” (last set of bars) is the 30 year average (1981-2010) extent at this date.1 It is clear from the graph that the 2013 extent was virtually identical to the 30-year average. Map from Wikipedia.
What puzzled me was why they featured only the last 7 years when satellite data go back to at least 1979. Is there something in that data they don’t want us to see?
There is no similar data in graph form available that I could find but there is the wonderful comparative sea ice mapping tool provided by Cryosphere Today, operated by the University of Illinois.
So, in the absence of numerical data to compare to the Fig. 1 graph, I chose visual data to ask the question: what could there be about the long-term record of Chukchi/Beaufort sea ice data that the NSIDC might not want us to know?
The ice coverage at mid-summer (July 12) provides a snapshot of what sea ice conditions are like for polar bears before the summer melt season gets into full swing, so this historical perspective is quite revealing. [See previous posts here, here, and here for more on Chukchi/Beaufort polar bears.]
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Comments Off on Chukchi-Beaufort ice extent comparison – why feature only the last 7 years?
Posted in Sea ice habitat
Tagged 30 year baseline, Beaufort Sea, Chukchi Sea, climatology, Cryosphere Today, NSIDC, polar bear status, sea ice extent, summer sea ice
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