You may or may not have noticed that even though Chukchi Sea ice coverage has been way below average this melt season, there has been no hue-and-cry about poor suffering Chukchi polar bears. That’s because polar bear biologist’s own research has shown that the health and survival of these bears has not been negatively impacted by low summer sea ice. There may be threats from poaching in Russia, but not lack of summer sea ice.
As of this date, developing sea ice is only just approaching Wrangel Island, a major polar bear denning region in the Chukchi Sea, see maps below (Ovsyanikov 2006).
Yet, polar bear specialists insist that neighbouring Beaufort Sea bears – who endure a much shorter open-water season – are in peril of extinction because of scarce summer sea ice.
There may not be ice for Western Hudson Bay polar bears to walk on yet but there is still more ice forming along the northwest shore of the bay than last year at this time or even the year before. The Canadian Ice Service (CIS) map for 5 November shows this early formation.
What’s present is mostly grey ice defined by CIS as:
“Young ice 10-15 cm thick, less elastic than nilas [a kind of new ice] and breaks on swell. It usually rafts under pressure.”
Polar bears generally need ice about 30 cm thick to support their weight, which could take a day or two – or a week or two, depending on the weather in northwestern Hudson Bay. For Churchill, along the central coast of western Hudson Bay, ice thick enough for walking will not likely be far behind, given the long-range forecast of freezing weather. In recent years, most Churchill polar bears have left the ice by around 20 November. More maps and graphs for this week below.
Great news for Western Hudson Bay polar bears! Following up from sea ice conditions last week, CIS maps show ice forming all along western Hudson Bay – not a huge amount, but the beginning of the end of the ice-free season, which recently has not occurred until mid-November (Cherry et al. 2013).
There is above-average sea ice coverage in Foxe Basin and Davis Strait, and only slightly below average coverage in the Beaufort Sea (see graphs below). Polar bear habitat is shaping up very nicely indeed across Canada and the US this year.
Good news for Southern Beaufort polar bears! Sea ice converging on the north shore of Alaska earlier than any year since 2011 at least, according to NSIDCs regional ice plots (below).
But wait, their Masie ice maps show it’s actually the earliest since 2008 (although the ice movement onshore was also earlier than 2006 and 2007, see below). And it’s still a full week before the end of October, the first month of Arctic fall (October-December). Lot’s of seal hunting habitat.
This emphasizes the fact that the primary problem faced by Southern Beaufort sea polar bears is not scarce summer ice but by thick sea ice conditions in the spring. Bears photographed near Kaktovik this year were in excellent condition (see here and here, taken by Kelsey Eliasson, Polar Bear Alley). If folks have been seeing starving bears, they haven’t said anything that I’ve been able to find.
Ice maps below.
Fall is the season when polar bears that have spent the summer fasting can return to the refreezing sea ice to resume successful hunting. For polar bears, fall is the second-most important time of year for hunting, after spring.
The date when freeze-up occurs across the Arctic varies from place to place and year to year, but the process is well underway this year. The US National Snow and Ice Data Center’s MASIE map for 20 October 2015 (above) shows 7.7 mkm2 of sea ice, up from the annual low of 4.41 mkm2 almost 6 weeks ago.
In The Arctic Journal, 7 October 2015: Unstable thinking about polar bear habitat [not my title choice]
This is a previously unpublished summary, written exclusively for The Arctic Journal, of my peer-reviewed, fully referenced essay on this topic that was published earlier this year by the Global Warming Policy Foundation in their “Briefing Paper” series (#16, June 8, 2015: The Arctic Fallacy: Sea Ice Stability and the Polar Bear), which includes a foreword by Dr. Matthew Cronin, Professor of Animal Genetics at the University of Alaska Fairbanks. Pdf here.
Here are the essential points, one by one:
Posted in Conservation Status, Sea ice habitat
Tagged Arctic Journal, decline, GWPF, habitat, IUCN, polar bear, population size, sea ice, spring, summer, thick spring ice
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
At this time of year, sea ice extent numbers are meaningless for polar bears. The extreme low September minimum of 2012 – when masses of polar bears didn’t die – showed rational people that this is true. Even the low 2007 summer extent, which hit earlier in the season than 2012, had little to no negative impact.
In late summer, bears outside the Canadian Archipelago either retreat to shore or stay on the sea ice as it retreats north into the Arctic Basin (see image below, click to enlarge). Most bears in the Archipelago have ice year round, so life doesn’t change much. This means that it does not matter to polar bears how much area the Arctic Basin ice covers in September – for their needs, 1.0 mkm2 would be plenty.
Still, Southern Hudson Bay polar bears had extended hunting opportunities in July this year (whether or not they hunted successfully) and for this date, Hudson Bay had more ice remaining than any year on record. Yes, more than even 1992 but only by a few percent. See charts and maps below.
Posted in Life History, Sea ice habitat
Tagged Arctic basin, fasting, habitat, Hudson Bay, MASIE, minimum, passive microwave, polar bear, sea ice, September, starving, summer, thin ice
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
Sea ice in at least three Eastern Canadian polar bear subpopulations is well above normal for this time of year, which means many bears are likely not ashore yet. The same is true in the Beaufort and Barents Seas – ice is melting but there is still a fair amount of sea ice close to popular shores. Cause for cheering, not raising alarms.
Southern Hudson Bay, Foxe Basin, and Davis Strait, all have above average sea ice coverage, according to the Canadian Ice Service (see charts below).
Hudson Bay ice levels are particularly striking: the anomaly map below (“departure from normal”) is almost entirely blue (positive), showing how far it is above average. No wonder supply ships needed icebreaker help yesterday to get into Inukjuak on the eastern shore. Most of the ice is technically in the Southern Hudson Bay polar bear subpopulation region, which has a stable population.
Posted in Conservation Status, Sea ice habitat
Tagged Beaufort, Davis Strait, habitat, Hudson Bay, melt, polar bear, science, sea ice, Southern Hudson Bay, summer, Svalbard