Sea ice in the Bering Sea this winter was said to be the lowest since the 1850s, largely driven by persistent winds from the south rather than the usual north winds although warm Pacific water was a factor early in the season (AIRC 2018). But what, if any, impact is this surprisingly low winter and spring ice cover likely to have on Chukchi Sea polar bear health and survival?
In fact, research on Chukchi Sea polar bears has included so few examples of individuals utilizing the Bering Sea in winter (Jan-March) and early spring (April-May) that any conclusions regarding an impact from this year’s sea ice conditions are likely to be invalid. In short, we don’t know what will happen since it has not happened before within living memory; the opinions of polar bear specialists must be taken with a grain of salt because so many of their previous assumptions have turned out to be wrong (Crockford 2017a,b, 2018), see here, here, and here. Seals, walrus and polar bears are much more flexible and resilent to changes in habitat conditions than most modern biologists give them credit for and consequently, it will be fascinating to see how the ice will change over the coming months and how the animals will respond.
Posted in Conservation Status, Life History, Sea ice habitat
Tagged Bering Sea, Chukchi Sea, facts, fast, feeding, habitat, hunting, ice-free period, mating, polar bear, science, sea ice, seals, starving
Sea ice extent in the Arctic is a bit below average this year at mid-winter but there are no data to suggest this situation will have a negative impact on polar bears.
[Photo above is sea ice off the coast of Labrador, Canada on 26 March 2007 (from Wikimedia): polar bears in the southern portion of the Davis Strait subpopulation have been particularly successful in recent years because in late March through May/June they hunt abundant numbers of young harp and hooded seals in this habitat]
Polar bear researchers presume that most animals eat little to nothing over the winter, because it explains why even non-pregnant bears are at their lowest weight at the beginning of spring.
Sea ice charts and maps below. Continue reading
There is still below average ice extent in the Barents Sea but there is no data whatsoever to indicate that this situation poses a problem for polar bears, given that as far as researchers know, polar bears eat little or nothing during the winter. That’s why the bears are at their leanest at the end of winter and why seal pups born in early spring are such a critical food source.
Note on map below (from WUWT Sea Ice Page, marked; original here) that polar bears are not found in three areas that are included in the total Arctic ice extent figures: below-average or above-average ice in the Sea of Okhotsk, Baltic Sea, and Gulf of St. Lawrence have no impact on polar bear health and survival.
Additional ice maps below. Continue reading
Posted in Life History, Sea ice habitat
Tagged Baltic, Barents Sea, Derocher, facts, fast, Gulf of St. Lawrence, polar bear, risk, sea ice, Sea of Okhotsk, t, threatened, winter
Polar bear habitat in the Arctic Basin this year appears to have reached its apex days earlier than average. As of 12 September, freeze-up of Arctic sea ice had begun. Unless something dramatic happens over the next few days, this will make 2015 the earliest September minimum since at least 2007, using NSIDC data.1
The two lowest September ice extents (2007 and 2012) were also both later than average; this year’s minimum is the fourth lowest (see chart below).
Of course, all this fuss about how low the September minimum gets is irrelevant to polar bears: they are either on land or in the Arctic Basin, and virtually all are living off stored fat no matter where they are (see Arctic Basin bear here). What matters is when the refrozen ice reaches pregnant females that have preferred denning spots onshore (like in Svalbard) or for bears onshore waiting to return to the ice to hunt (like Davis Strait, and Western and Southern Hudson Bay bears). We won’t know that until October (for Svalbard) or November (for E. Canada).
Again, no sea ice death spiral or polar bears in peril because of it.
UPDATE 15 September 2015, 11:00 am PDT: Just published at the NSIDC website, 2015 minimum has been (tentatively) called at 4.41 mkm2, confirming my figure taken from their interactive graph (see below). However, despite the fact that their own data show that sea ice extent stayed at that value for three days, NSIDC has chosen the last day of that 3-day period rather than the first to represent the 2015 minimum. Go figure. That makes 2015 tied with 2011 for the earliest date for their official records, which seems more than a little self-serving and means I’m not changing the title of my post. NSIDC have also modified slightly some of the official extent figures for past minimums (added below) but it doesn’t really change anything.
Posted in Sea ice habitat
Tagged Arctic, death spiral, fast, freeze-up, habitat, MASIE, melt, minimum, NSIDC, polar bear, sea ice, September, summer
The longest-ever-recorded underwater dive by a polar bear, stalking three bearded seals, shows in striking fashion how truly difficult it is for a polar bear to catch a seal from summer sea ice. After the long dive, the bear (see below screen capture) erupts from the water to try and take the seal resting on the ice but it escapes.
The paper reporting this dive, by Ian Stirling and photographer and Arctic expedition organizer Rinie van Meurs, has hit the news again in a big way, as it finally appeared in print. I wrote about it in June here, when it came out in press. The video was shot on 19 August 2014, at the height of the Arctic summer (July, August, September).
CBC Radio posted the video and interviewed van Meurs yesterday (“As It Happens” 4 August), in which he reportedly made this astonishing statement:
“…after 27 years working, I have seen clearly changes in the sea ice. I don’t need to see the NASA records and graphs and all that.”
Indeed, who needs science and all that? You just have to look out the window of your ship! Anecdotal reports are what count as evidence to people who are not scientists. Van Meurs, who is not a scientist, is who the media gets to interview. Where’s co-author Stirling, the scientist?
More stills from the van Meurs video below – too bad, so sad, the bear gets no seal. Why polar bears eat little in the summer even if they are out on the ice hunting, as I discussed here.
Posted in Life History, Sea ice habitat
Tagged anecdotal reports, bearded seal, dive, evolution, fast, habitat, polar bear, science, scientific evidence, sea ice, stalk, summer, underwater
Most of these bears are close enough to shore to hit the beach if that’s where they wanted to be but they’re on the sea ice.
I’ve been posting these USGS tracking maps for two years.1 The map archive at USGS goes back to December 2009. Seeing all animals on the ice in July is usual for Southern Beaufort polar bears.
During August, a few of these females usually come ashore (see here and here), probably because they plan to den there later. But most polar bear females stay out on the ice, no matter how far it contracts into the Arctic Basin. Only about 5% of SB bears spend time on land during the summer.
See the July track map below and some sea ice maps and graphs for the region.
A polar bear paper just out in Science concludes the experts were wrong, polar bears are not “walking hibernators” – in summer, they slow down and live off their accumulated fat just like other mammals. Take home message: experts are not infallible and spring fat is critical for polar bear survival over the summer.
This paper presents no compelling evidence that Southern Beaufort polar bears, or those in any other region, lack the ability to survive predicted summer sea ice declines in future decades – although they claim it does. See what you think.
Posted in Life History, Sea ice habitat
Tagged Alaska, Amstrup, Arctic Fallacy, Beaufort Sea, Ben-David, fast, fat, hibernation, polar bear science, polar bears, Regehr, sea ice, Southern Beaufort, summer, temperatures, walking hibernator, Whiteman