Sea ice adjacent to all major polar bear onshore summer refugia at 31 July 2019

For all the hand-wringing over sea ice extent this year and its supposed similarity to 2012, what is truly remarkable is that at the end of July ice remains adjacent to every single major terrestrial summer refugia known to be important for polar bears. Those refugia sites include (from west to east, starting in the Chukchi Sea): Wrangel Island, western Chukotka, Severnaya Zemlya, Franz Josef Land, East Greenland, virtually all the islands of the Canadian Arctic Archipelago (including Southampton Island in Foxe Basin and the southwest and eastern coasts of Baffin Island), and Western Hudson Bay.

masie_all_zoom_4km 2019 July 31

Few bears spend the entire summer onshore along the Alaska coast: most still spend the summer on the sea ice and move with it as it contracts toward the Arctic Basin, as do many bears in the Barents, Kara, East Siberian, and Chukchi Seas. Until a few weeks ago, however, there was enough ice present that Beaufort Sea bears could go ashore if they wanted to do so.

2012 conditions

For comparison, here is what Arctic ice extent looked like in 2012 at the end of July, see a close-up here: more ice in the western Arctic (Chukchi Sea) but less in the east (especially the Barents Sea and Hudson Bay.

Sea ice 2012 July 31 MASIE long view

Just a note to keep in mind: there was not a huge die-off of polar bears in 2012 or the following winter. There is no evidence the low summer sea ice extent that occurred in 2012 (or in 2007) had any significantly negative effect on polar bear survival – see my new book (The Polar Bear Catastrophe That Never Happened) for details.

Hudson Bay

The blue in the chart below from the Canadian Ice Service for the last week of July 2019 shows a substantial amount of ice present that is more than average in Hudson Bay and on the southwest coast of Baffin Island:

Hudson Bay weekly departure from normal 2019 July 29

The ice that remains in Hudson Bay is shown in the chart below as thick first year ice (> 1.2 m thick), although satellites at this time of year have a hard time distinguishing melt ponds on ice from open water. As a consequence, the amount of ice present is strongly underestimated, especially if it is of low concentration:

Hudson Bay weekly stage of development 2019 July 29

The most recent report from polar bear researcher Andrew Derocher on the location of bears his team had tagged earlier this year shows almost half were still on the ice as of 27 July (see below). The reason that so many bears seem to be on ice that doesn’t exist is primarly because Derocher uses a filter for these maps that only shows ice that is >50% concentration:

Derocher 2019 WHB 12 pbs ashore 12 still on ice with some unaccounted for at 27 July chart

Derocher has finally admitted in public that polar bears have little chance of catching a seal at this time of year: summer hunting success is poor during summer in part because there is so much open water but also because the naive young seals they depend upon are out in open water feeding.

In other words, the reason that polar bears easily survive an onshore fast of 4-5 months over the late summer/early fall is that they would get very little to eat (if anything) even if they stayed out on the ice. It’s the fat put on in spring/early summer (from gorging on baby seals) that carries them over the summer, no matter where they choose to spend it. And because ice conditions in spring across the Arctic have been good so far, with abundant prey, polar bears are thriving despite the recent decline in summer sea ice.

The bears seen so far near Churchill in Western Hudson Bay have been in very good condition. Latest problem polar bear report is copied below (the 3rd of the season), see discussions on the other two here.

Churchill problem bears_week 3_2019 July 22-28 posted July 30

Svalbard and the Barents Sea

The chart below shows ice in the Barents and East Greenland Seas at the end of July, with Franz Josef Land (an important summer refuge and denning area) on the far right. Ice breakers headed for the North Polar earlier in the season had trouble navigating this area of sea ice:

Barents Sea ice extent 2019 July 31_NIS

According to the Norwegian Ice Service, sea ice coverage for the area around Svalbard alone was still above the long term average at the end of July:

Svalbard ice extent 2019 July 31_graph_NIS

Beaufort Sea

While there is less ice than usual in the Beaufort Sea off Alaska, what is present is mostly very thick multi-year ice mixed with thick first year ice (> 1.2 m) that’s a perfect refuge for polar bears over the summer:

Western Arctic weekly stage of development 2019 July 29

For the Western Arctic as a region, Canadian Ice Service data shows this year is not the lowest it’s ever been at the end of July, although it is lower than usual:  the lowest extent since 1981 occurred in 2012 (although 1998, 2008, 2011 and 2016 were almost as low).

Western Arctic Alaska historical ice cover same week 2019 July 29

So far, I have seen no reports of polar bear activity onshore in Alaska and although there is almost certainly a few present, it appears none of them are causing trouble.

 

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