So, here we are near the end of the first month of the Arctic spring and there is still more ice than usual off Labrador and conditions in the Barents Sea are improving daily. The fear-mongers can blather all they like about the potential risks of bears swimming in summer – but spring is the critical season as far as sea ice is concerned for polar bears and all polar bear biologists know it. Polar bears consume 2/3 of all the food they need for the year during April-June and so far, ice conditions are looking just fine.
There is enough ice where there needs to be ice for polar bears to gorge themselves on new-born ringed and bearded seals – and that’s really all that matters. More ice off Labrador means more hunting ground for the Davis Strait polar bears that depend on the tens of thousands of young harp seals born this year off the Front.
Posted in Life History, Sea ice habitat
Tagged bearded seal, facts, feeding, harp seal, hunting, Labrador, polar bear, polynya, ringed seal, sea ice, Southern Beaufort, Svalbard
Polar bear habitat in the Southern Beaufort for May 2015 was a contrast between the development of recurring polynyas (patches of open water) and tremendously thick sea ice. So it’s interesting to see where the polar bears tagged by USGS biologists chose to hang out.
The total number of bears being tracked in May – 23 – is down markedly from the 30 bears USGS biologists started with in April.
Most of the collared bears were concentrated in May along the shore lead (crack of open water) that normally develops between the shorefast ice and the pack ice offshore. That’s especially understandable this year, since most of that pack ice is 3-5 m thick (10-16 ft) – see the maps below.
Posted in Sea ice habitat
Tagged Beaufort Sea, Chukchi Sea, habitat, open water, polar bear, polynya, satellite collars, sea ice, shore lead, spring sea ice, thick ice, tracking, USGS
Hudson Bay sea ice coverage is only slightly below average for this time of year (week of 14 May, below) but well above levels for 2006, when Western Hudson Bay breakup was relatively early).
Figure 1. Sea ice coverage over Hudson Bay for the week of 14 May, 1971-2015. Canadian Ice Service. Click to enlarge.
Even at its highest extent in April, Hudson Bay is only 97-98% ice covered (due to persistent shoreleads and polynyas), which means ice levels are currently only 10% or so below maximum. In other words, there is still lots of polar bear hunting habitat over the bay.
That’s a bit lower than ice coverage was for the last two years at this date (2013-2014), which had average or above average ice cover. However, there is currently a bit more ice on Hudson Bay than there was in 2011 and 2012 – and much more than there was in 2010 and 2006.
With masses of very thick, multiyear ice off Alaska this spring, the developing polynyas (open water) at either end of the Beaufort Sea are providing essential polar bear hunting habitat.
Patches of open water in the Beaufort Sea are naturally recurring phenomena. This year we have two excellent examples, shown by the yellow arrows in the sea ice thickness map above (from the Naval Research Laboratory).
The eastern-most polynya forms in the Canadian portion of the Beaufort most years in the spring. This open water feature is so common it has a name – the Cape Bathurst polynya. Last year, there wasn’t an obvious polynya there until sometime in June, but in 1975, a patch of open water almost as large (or larger) as this year’s had developed by the end of May (Fig. 1).
Figure 1. Cape Bathurst polynya at 28 May 1975 (Smith and Rigby 1981:Fig. 14h) and the polynya this year at 14 May (Canadian Ice Service). See discussion in the text below about the relative sizes. Click to enlarge.
According to the experts that study them, the timing and extent of the polynya formation depends on wind (Dunbar 1981:29), not temperature. This means that this spring’s polynya formation in the eastern Beaufort isn’t a symptom of global warming, it isn’t “missing polar bear habitat,” and it isn’t a sign of early sea ice breakup.
In fact, the Cape Bathurst polynya is a critical place for ringed seals and bearded seals to congregate in spring. Therefore, this is where many Southern Beaufort polar bears go to hunt. The presence of the polynya is especially crucial in years like this one, when very thick sea ice covers most of the Beaufort Sea. Continue reading
Posted in Life History, Sea ice habitat
Tagged Alaska, Arctic, bearded seal, Beaufort Sea, Cape Bathurst, Cleator, ice thickness, open water, Point Barrow, polynya, ringed seal, sea ice, spring, Stirling