Tag Archives: polynya

Polar bear habitat update mid-May: little change since 1989 despite CO2 increase

Sea ice habitat for polar bears has not become progressively worse each year during their season of critical feeding and mating, as some scaremongers often imply. It’s true that absolute extent of Arctic ice is lower this spring than it was in 1979. However, according to NSIDC Masie figures, polar bear habitat at mid-May registers about 12 million km2, just as it did in 2006 (although it is distributed a little differently); other data show spring extent has changed little since a major decline occurred in 1989, despite ever-rising CO2 levels.

Polar bear feeding_Shutterstock_sm

In other words, there has been virtually no change in sea ice cover over the last 12 years, despite the fact that atmospheric CO2 has now surpassed 410 parts per million, a considerable and steady increase over levels in 2006 which were about 380 ppm (see below, from the Scripps Oceanographic Laboratory, included in the Washington Post story 3 May 2018):

Scripps CO2 curve at 29 April 2018

Not only that, but if rising CO2 levels were responsible for the decline of sea ice and implied effects on polar bears since 1979 (when CO2 levels were around 340 ppm), why has spring ice extent been so variable since 1989 (when the first big decline occurred) but so little changed overall since then? See the NSIDC graph below for April:

Sea ice 2018 April average_NSIDC graph

This year on day 134 (14 May), global ice cover registered 12.3 mkm2:

masie_all_zoom_4km 2018 May 14

In 2016 on the same day, the overall extent was much the same but there was more ice in the Chukchi and Bering Seas and less in the eastern Beaufort:

masie_all_zoom_4km 2016 May 14

More close-up charts of different regions below for 2018 vs. 2016, showing more detail.

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Polynya refresher: open water in spring is due to winds & currents, not ice melt

Arctic sea ice begins to open up in spring at predictable locations due to currents and prevailing winds and this was as true in the 1970s as it is today. Polynyas and widening shore leads that most often get mistaken for early sea ice melt are those in the Beaufort and Chukchi Seas and in Hudson Bay.

Beaufort Sea male polar bear USGS_2005 Amstrup photo

But contrary to concerns expressed about possible negative implications of these early patches of open water, these areas have always been critical congregation areas for Arctic seals and are therefore important feeding areas for polar bears.

Seal habitat frozen open lead_Beaufort 2008_Miller

Seals hauled out beside a lightly frozen over lead in Beaufort Sea ice, 2008. USFWS.

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Southern Beaufort sea ice melt in May: good news for polar bears or catastrophe?

Last week biologist Andrew Derocher recently implied via twitter that less sea ice in the eastern portion of the Southern Beaufort (SB) this year at mid-May is harmful to polar bears (calling it “a hole in the ice where polar bears used to live“), but both long-term and short-term data don’t support such a glass-half-empty interpretation.

Not only does spring breakup of sea ice in the SB normally begin with such open patches of water (see the video above from last year) — driven by the powerful currents of the Beaufort Gyre, not ice melt (explained in detail here) — it may actually be necessary for the survival of local seals, polar bears and whales in spring and early summer (Citta et al. 2015; Crawford et al. 2015; Harwood et al. 2015; Stirling et al. 1981).

As I’ve pointed out before, the biggest threat to SB bears is thick sea ice in spring and its associated late breakup, a 2-3 year-long phenomenon unique to this region known to have occurred about every 10 years since the early 1960s (well documented in the scientific literature) but which has not (as far as I know) happened since 2004-2006.

In other words, a considerable patch of open water and less concentrated ice in the eastern SB around Cape Bathurst is almost certainly a good thing for this particular subpopulation (see previous post here for an in-depth discussion) because historically, when a polynya of some extent has not formed by April or May it has been devastating for local marine mammals.

The fact that an extensive patch of open water existed at mid-May in this region last year and the year before (2015 and 2016) — with no public hue-and-cry about a great dying of SB bears from Derocher or anyone else — suggests that open water in the eastern SB this year is likely to be beneficial for SB polar bears, or at least benign. Continue reading

Ice maps vs. observations in the W. Arctic – polar bear habitat reality check

Last Wednesday (8 June 2016), the US Coast Guard rescued walrus hunters from Shishmaref in the Bering Strait who got stuck in sea ice that is barely visible on sea ice maps. It’s a rare glimpse of what sea ice really looks like up close compared to what you see on the ice maps.

Watch the video here: https://www.dvidshub.net/video/embed/467959

[Unfortunately, the screencaps from the video, like the one below, are less impressive than the film. In the video, you can see the hunters walking on the ice around their trapped boat – the ice does not visibly move]

Shishmaref_ice_CoastGuard 02_8 June 2016

Have a look at the sea ice maps below for the day the incident took place. They show what appears to be hardly any ice in the area.

This is a good lesson for assessing what’s been going on in the Beaufort Sea a bit further east, where winds and currents have opened up a rather large patch of open water surrounded by considerable expanses of sea ice – at issue is the possible impact on polar bear spring feeding for April and May.
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Beaufort Sea fractured ice due to strong Beaufort Gyre action – not early melt

The Canadian Ice Service has a cool NASA animated video showing the Beaufort Gyre in action – you can actually see the solid mass of ice crack and swirl west and north under the pressure of the massive corkscrew current – see original here (tips on getting yourself oriented in the video below the screencap) and view below, for Apri 4- May 3, 2016:

Beaufort Gyre video screencap_21 April 2016_labelled

Note that the video is oriented with Banks Island on the bottom and the shore of Alaska along the left-hand side, as if the locator map provided was rotated as below:

Beaufort Gyre video screencap_locator map_rotated

The big ‘bite” of ice being torn out to the south of Banks Island is the Amundsen Gulf.

The caption for the NASA video says this (my bold):

“MODIS Terra imagery taken between April 4 and May 3, 2016 of the Beaufort Sea. The animation highlights the gradual ice breakup due to the Beaufort gyre.

So, early breakup here is due to Beaufort Gyre action – not early seasonal melt.
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Tracking polar bears in the Beaufort Sea in April 2016 and early polynya formation

putting_collar_on_polar_bear_slider_USGS

Here’s the update on the polar bears fitted with satellite collars or ear tags in the Beaufort by USGS biologists over the last two years. Five new bears were added last month, which means there are now thirteen bears being tracked. Ice conditions are somewhat different than they have been in the past but concluding that such a situation means trouble is premature, I think (see here). Continue reading

Polar bear habitat update end of April 2016: Plenty of sea ice for feeding

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.

Cambridge Bay_we re OK_from Joe Prins

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.

Harp seal pup_DFO Newfoundland
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