Tag Archives: habitat

2015 may be the earliest in many years that W. Hudson Bay polar bears head for the sea ice

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).

Canadian Arctic Oct 29 2015_CIS

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.
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Beaufort Sea polar bear habitat highest since 2008 at this date

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).

r01_Beaufort_Sea_ts_4km

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.
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Winter returns to the Arctic – freeze-up 2015 at October 20 expands polar bear habitat

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.

masie_all_zoom_4km_2015 Oct 20

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.

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Sea ice is not a stable habitat for polar bears – summarized today in The Arctic Journal

In The Arctic Journal, 7 October 2015: Unstable thinking about polar bear habitat [not my title choice]

Unstable thinking about polar bear habitat_Oct 7 2015 title page

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:
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September minimum 2015 looks like the earliest end of Arctic melt season since 2007

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

masie_all_zoom_v01_2015252_4km

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.
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Summer habitat for most polar bears is either shoreline or sea ice in the Arctic Basin

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.

Greenland W coast_Female w cubs_2006_Mads Heide-Jorgensen_NOAA sm

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.

Sea ice and summer refuges for polar bears_17 Aug 2015

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.

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Long underwater stalk by polar bear shows how hard it is to catch seals in 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.

Underwater stalk_01

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.

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Polar bear habitat update: Eastern Canada well above normal, lots of sea ice worldwide

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.

Stirling 01 no date_sm

Southern Hudson Bay, Foxe Basin, and Davis Strait, all have above average sea ice coverage, according to the Canadian Ice Service (see charts below).

Sea ice concentration in Canadian waters at 23 July 2015. Canadian Ice Service. Click to enlarge.

Sea ice concentration in Canadian waters at 23 July 2015. Canadian Ice Service. Click to enlarge.

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.

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Alarm over future summer polar bear habitat disguises how good conditions are right now

Despite the public outcry last week over future polar bear survival, the polar-bears-are-doomed crowd can’t hide the fact that this year, spring sea ice habitat for polar bears worldwide has been excellent.

A polar bear walks on the Arctic Ocean ice Aug. 21, 2009.

This year on 19 July, for example, Hudson Bay had greater than 150,000 square km more sea ice than there was in 2009 on that date (526.2 vs. 368.5 mkm2)(1992 was a particularly cold year and most bears left the ice as late in 2009 as they did in 1992).1 Conditions have also been excellent for pregnant females around Svalbard – Norwegian polar bear researchers recently reported a good crop of cubs this spring.

Hudson Bay breakup July 20 2015_CIS

Worldwide, there was exactly the same amount of Arctic sea ice present on 18 July 2015 as there was back in 2006 (Day 199) – 8.4 mkm2. By 19 July (day 200), 2015 had more ice than 2006 (8.4 mkm2 vs. 8.3).

All this means that recent summer ice melt has not impinged on the spring feeding period that is so critically important for polar bears. So much ice left in early summer means there was lots of sea ice in the spring (April-June), even in the Southern Beaufort Sea.

The only region with sea ice coverage well below the last five years is the Chukchi Sea (see plots below, click to enlarge). So why aren’t we hearing the-sky-is-falling stories about Chukchi bears? Because biologist have already demonstrated that polar bears in the Chukchi do very well even with no summer sea ice.
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Polar bear habitat looking good for early summer – last days before the fast

Some polar bears may already be living mostly off the fat put on over the spring but others may catch a seal or two on the sea ice before the summer fast begins – since the ice hasn’t left the coast in most regions quite yet. Polar bears eat little in summer, whether they spend their time on land or on the sea ice.

PolarBearCV1LG_USGS

Sea ice is still high over Hudson Bay – for this time of year, it hasn’t had this much polar bear habitat since 2009. Davis Strait and Foxe Basin are also above average – Davis Strait hasn’t had this much ice since 1992 (the Mt. Pinatubo cold year). Polar bear subpopulation refresher map below.

PB map-all-populations PBSG original plus Okhotsk
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