Polar bear habitat update at mid-June: more than enough for survival

Here we are at the middle of June, when most polar bears are pretty much done with hunting seals for the season. And despite hand-wringing from some quarters, sea ice extent is down only marginally from average at this time of year and certainly not enough to impact polar bear survival.

Given the large expanse of open water in the Southern Beaufort so early in the season, one resident pessimist insists those polar bears are “challenged” by the lack of ice. If he is right, there should be reports of dozens upon dozens of skinny and dying bears along the coast of Alaska this summer. If not, he will pretend he never suggested any such thing.

So far, despite the early loss of ice in some regions, there have been no reports of polar bears ashore unusually early. Hudson Bay still has lots of thick first year ice, so despite the overall reduced Arctic ice coverage, none of the three Hudson Bay polar bear populations are facing the earlier-than-usual sea ice breakup this year as we keep being promised will show up. In fact, there hasn’t been a significantly early breakup in Western Hudson Bay since 2010 (see previous posts here and here).

Arctic in General

From NISDC at 13 June, 2019 (gold) compared to 2012 (dashed line) and 2018 (blue):

From NSIDC Masie at 13 June 2019:

Compare above to 2017:

Canada (home to about half the worlds polar bears)

Sea ice in Canada on 14 June 2019, with abundant ice everywhere except the coast of Labrador in the east and the Southern Beaufort in the west:

Compare the above to 2017 on the same date:

Beaufort Sea

‘Departure from normal’ chart from Canadian Ice Service below shows a lot of red (less than average) for the week of 10 June 2019, indicating lots of open water:

Looks bad, right? However, what ice that is left is primarily thick first year ice (dark green, >1 m thick) or metres-thick multi-year ice (brown), with solid patches of it along the shore (i.e. shore-fast ice). Keep in mind that ice edges are where seals congregate, so that’s where most bears hang out at this time of year:

Polar bear specialist Andrew Derocher over the last week or so:

Rapid sea ice loss presents major challenges for #polarbears. There are 2 strategies for the summer: move to shore or go north with the ice. Neither is optimum. On land some bears feed on subsistence harvested bowheads. Going north is increasingly a bad option: big energy cost. https://t.co/KswbkpAKbS

— Andrew Derocher (@AEDerocher) June 6, 2019

Ice loss is a challenge for #polarbears & the farther summer sea ice moves offshore, the more problematic it becomes. The Beaufort Sea bears either move to land or follow the ice north. Following the ice 500+ km N & the same distance S in the autumn has energetic consequences. https://t.co/rD43tKmVpS

— Andrew Derocher (@AEDerocher) June 11, 2019

Hudson Bay

All of the dark green in the chart below is thick first year ice >1 metre in thickness (light green is thinner ice and blue is open water):

Compare the above to 2010 for the same week (an early breakup year):

Barents Sea

More or less average levels of ice in the Barents Sea this spring:

And this is what it looks like on a map:

Looking across the top of the Arctic (below, for Day 164 or 13 June 2019, via NSIDC Masie), we see more ice than in recent years in the east (Barents/Kara Seas) and less in the Chukchi Sea, but all in all, no major catastrophe for polar bears. Some will come ashore shortly for the summer fast while most will take to the ice: it’s what they have always had the ability to do. Bears that have feed well over the spring do not require sea ice to survive over the summer.

Bottom line: