Category Archives: Sea ice habitat

Melt season update – Bering Sea ice abundant & Davis Strait ice 2nd highest since 1971

Polar bear habitat in the eastern Bering Sea has expanded since the official spring “maximum extent” was called for late February, and Davis Strait sea ice is tied for 2nd highest since 1971 for this week. Both regions have healthy polar bear populations and spring conditions suggest this will continue into this year.

Rode and Regehr 2010_Chukchi_report2010_Fig1_triplets_labelled

Although the melt season is underway, as of yesterday (22 April, Julian day 112) overall Arctic sea ice extent (Fig. 1) was higher than it was on the same date in 2014, 2007, and 2004 (see also Fig. 2). Despite the record low extent in February (Fig. 3), that pessimists at Polar Bears International suggested was relevant to polar bear heath and survival, I showed that was misleading.

Figure 1. Sea ice extent at 22 April (Julian day 112) for 2015, at 13.976 mkm2, was well within 2 standard deviations and higher than 2007 (shown) as well as 2004 and 2014 (not shown – see it for yourself here).

Figure 1. Sea ice extent at 22 April (Julian day 112) for 2015, at 13.976 mkm2, was well within 2 standard deviations and higher than 2007 (shown), as well as higher than 2004 and 2014 (not shown – see it for yourself here). Click to enlarge.

Sea ice maps and charts tell the story of current polar bear habitat throughout the Arctic.
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Polar bears barely survived the sea ice habitat changes of the last Ice Age, evidence suggests

While the polar bear is an Ice Age species, genetic and fossil evidence suggests it barely survived the profound sea ice changes associated with the Last Glacial Maximum, one of the most severe glacial periods of the Pleistocene.

polar_bear_usfws_no date_sm

A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals.

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Spring ice alarm deflated – 2015 ice now as high as 2014 & Davis Strait highest since 1971

Arctic ice extent (at 14.1mkm2) on 15 April, was virtually identical to 2014 on that date, and higher than 2006. But the record goes to Davis Strait, which recorded the highest ice extent since 1971 for the week of April 16, while the waters of Eastern Newfoundland to the south (where most harp seals have their pups) had the third highest ice extent since 1969. Lots of fat baby seals are just what polar bears need at this time of year.

Harp seal pup_DFO Newfoundland

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Polar bear habitat update: highly concentrated ice in eastern Hudson Bay this spring

Sea ice in eastern Hudson Bay (bright white in the map below) is more concentrated than at this time last year and similar to the ice found in the Central Canadian Arctic.

Sea ice extent Canada 2015 April 11 CIS

There is more concentrated ice (10/10 concentration) in the east side of the Bay than there was in 1992, a heavy ice year blamed in part on the eruption of Mt. Pinatubo (Chambellant et al. 2012) that resulted in the latest breakup date for Western Hudson Bay since 1991.

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Challenging polar bear fearmongering about Arctic sea ice extent for March 2015

Here are some facts to counter the misinformation and fearmongering being spread via twitter by a polar bear biologist who is getting carried away with his conservation activism.

Arctic Sea ice extent March greater than PB habitat_April 12 2015

Following up on my last post, I note that Arctic regions with sea ice but not polar bears were about 0.32 mkm2 below last year’s March average extent – which means the total ice decline from 2014 (0.4 mkm2) represents only a slight decline in polar bear habitat, most of which is in the Barents Sea (and due primarily to the state of the AMO, not global warming).

Sea ice extent for the Sea of Okhotsk and Baltic Sea combined (both areas without polar bears)1 were about 0.6 mkm2 below average this year for March. Average extent for March (according to NSIDC) is 15.5 mkm2, which means this year’s extent (14.4 mkm2) was 1.1 mkm2 below average, of which less than half (0.5 mkm2) was “lost” polar bear habitat.

IUCN Polar Bear Specialist Group biologist Andrew Derocher has been saying this is a “huge loss for polar bears” (see below): rational analysis of the facts show it is not. Continue reading

Arctic sea ice extent total for March does not equal global polar bear habitat

Only half or less of the estimated 2.6% loss per decade of March sea ice extent since 1979 (Fig. 1, below) represents a decline in polar habitat. That’s because several regions with sea ice that are not home to polar bears, like the Sea of Okhotsk, are included in Arctic sea ice totals.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015, which includes ice in the Sea of Okhotsk and the Sea of Japan, a decline of 2.6% per decade. NSIDC, March summary 2015.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015 (which includes ice in the Sea of Okhotsk, the Sea of Japan, and the Baltic, where polar bears do not live), shows a decline of 2.6% per decade. NSIDC, March summary 2015.

Both the Sea of Okhotsk and northern Sea of Japan (Fig. 2) have sea ice in winter (which is included in total Arctic sea ice records) but they are not truly “Arctic” – neither is connected to the Arctic by continuous ice, even when the ice is at its maximum extent (nor is the Baltic Sea — in contrast to Hudson Bay and the east coast of North America, which are connected to the Arctic by continuous ice).

Sea of Okhotsk_1979 March marked_PolarBearScience

Figure 2. Location of the Sea of Okhotsk and Sea of Japan. Insert ice map for March 1979 from NSIDC shows it’s position relative to the Arctic proper.

That lack of connection to Arctic pack ice is probably the main reason that polar bears never colonized the Sea of Okhotsk, even though western Arctic seal species (ringed, bearded, spotted, and ribbon) and Arctic whales  (bowhead and beluga) live there. Polar bears don’t currently live in the Sea of Okhotsk and all evidence suggests they never have.

Sea ice maps show that about half of the total ice extent difference between March 1979 and March 2015 was due to a relatively large decline in sea ice cover for Sea of Okhotsk and northern Sea of Japan — regions without polar bears. Surely no reputable scientist or journalist would suggest that the “record low” maximum ice extent for 2015 has any relevance for polar bear health and survival? [or for Northwest Passage travel, for that matter] Sadly, they would.

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Tracking polar bears in the Beaufort Sea – March 2015 map

Here is the March 2015 follow-up to my post on the July 2013 track map for female 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 USGS track map for March 2015 is copied below.

Three out of eight female bears tagged in the Southern Beaufort Sea were in the Chukchi Sea subpopulation region during March – not surprising, many bears cross this “boundary.”
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