Winter sea ice habitat for polar bears still abundant enough to sustain a thriving species

From Polar Bear Science

Susan Crockford

In contrast to summer sea ice, winter ice in the Arctic was again abundant this year. The slight decline since 1979 has so far been no cause for concern to polar bears, who are thriving.

According to the US National Snow and Ice Data Center report (5 April 2023), the average ice extent for March was 14.44 mkm2, considered the “winter”value (as compared to “summer” which is the average for September). The extent for this year was certainly below the long-term average but nowhere near being gone for good and nowhere near the low extent for winter at the height of the Eemain interglacial, when there was no ice at all in the Bering Sea (Polyak et al. 2010).

Numbers don’t tell the whole story. Critically for polar bears, there was abundant ice in every subpopulation region where the species depends on newborn seals for food at this time of year, from the Bering Sea to the Barents Sea. There is even a fair amount off southeast Greenland, home to the newest subpopulation of bears.

While some researchers and the media focus on the fact that some Arctic ice is getting thinner, this is not an issue for polar bears who require ice less than 2 m thick at this time of year (Derocher et al. 2004).

That means abundant first year ice, especially near shore and over Hudson Bay (shown below), is excellent news for polar bears.

In their 2004 paper, Derocher and colleagues state this unequivocally in the first sentence of their abstract:

Polar bears (Ursus maritimus) live throughout the ice-covered waters of the circumpolar Arctic, particularly in near shore annual ice over the continental shelf where biological productivity is highest.

That means abundant first year ice, especially near shore and over Hudson Bay, is excellent news for these species.

Moreover, a study by George Durner and colleagues (2019:8625) on the use of sea ice in summer and winter by Southern Beaufort Sea polar bears over two recent decades (1996-2006 and 2007-2016) compared to a 1985-1995 decade baseline concluded:

During the ice maximum season (i.e., winter), polar bears used the best habitat available, which changed relatively little across the three decades of study.

Ian Stirling and colleagues (1999:294) could not have said it more clearly in their paper about Western Hudson Bay polar bears:

Polar bears reach their lightest weights of the year in late March, just before the birth of the next cohort of ringed seal pups. This fact suggests it is the success of their hunting in spring and early summer that enables them to maximize the body reserves necessary for survival, reproduction, and nursing of cubs through the rest of the year.


Derocher, A.E., Lunn, N.J., and Stirling, I. 2004. Polar bears in a warming climate. Integrative and Comparative Biology 44(2):163-176.

Durner, G.M., Douglas, D.C., and Atwood, T.C. 2019. Are polar bear habitat resource selection functions developed from 1985-1995 data still useful? Ecology and Evolution 9(15):8625-8638.

Polyak, L., Alley, R.B., Andrews, J.T., et al. 2010. History of sea ice in the Arctic. Quaternary Science Reviews 29:1757-1778.

Stirling, I., Lunn, N.J., and Iacozza, J. 1999. Long-term trends in the population ecology of polar bears in Western Hudson Bay in relation to climate change. Arctic 52(3):294-306.

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April 15, 2023 6:10 am

The maximum arctic ice extent in 1974 was the same at 14.4 mkm2 (Parkinson and Cavalieri, 1989).

Steve Case
Reply to  Scissor
April 15, 2023 7:22 am

The IPCC used to show that, but it’s been fudged and finally removed from their charts:

Sea Ice Extent 5 graphs.jpg
Reply to  Steve Case
April 15, 2023 8:55 am

The drift to grift began around 1990 and accelerated between 1995 and 2000.

Joseph Zorzin
Reply to  Scissor
April 15, 2023 9:45 am

sounds like a grift emergency! 🙂

Reply to  Joseph Zorzin
April 15, 2023 9:57 am

Or maybe a crisis.

Chris Norman
Reply to  Scissor
April 16, 2023 10:45 pm

Do you have a link?

Tom Halla
April 15, 2023 6:28 am

If you think it through, the seals, and therefore the bears, need ice edges, not solid ice coverage.

Steve Case
April 15, 2023 6:43 am

It’s always important to note what the mainstream media doesn’t report, and out of the first 20 Google (News) searches, only one came up with the usual crap:

     The Washington Post
     Why Russia’s war in Ukraine is bad news for polar bears

If you followed the link, we are told that monitoring polar bears on Wrangle Island has been interfered with:  

     Dino Grandoni writes:
     “The loss of knowledge of polar species in particular comes at a crucial time
     in the Arctic, a region warming faster than anywhere else in the world.” 

general custer
April 15, 2023 6:56 am

Polar bears! While the ecofolks love to worry about these animals they certainly have no wish to see them wandering in their neighborhood. In fact, if sacred species like pandas were digging through suburban trash dollies there would be requests for a bounty on the cuties. Coyotes, a close relative of the family pets, are deemed a threat to society now.

Joseph Zorzin
Reply to  general custer
April 15, 2023 9:48 am

supposedly, they’re now see frequently in Boston

Ron Long
April 15, 2023 8:02 am

Yahoo for another report, from Dr. Susan, showing our brother, the Polar Bear, once upon a time an indicator species for Global Warming, is thriving. However, I’m a little conflicted, cheering on an Apex Predator, who like appetizers of all flavors.

Reply to  Ron Long
April 15, 2023 9:55 am

Some experiments concerning polar bears and their choice of appetizers would be very interesting.

Ron Long
Reply to  Scissor
April 15, 2023 10:11 am

Do you mean like AlGore?

April 16, 2023 8:12 am

Worth remembering, prior to the last ice age that began approximately 2.4 million years ago, yesterday in geologic time, there was no such thing as polar bears. They did not exist as a species.

The north coast of greenland was a temperate arboreal forest with temps 50 degrees warmer than today. There was NO ice at the north pole, or very little. No glaciers in Greenland to speak of.

The human species had just emerged. Lucy, the autralopithecus afarensis famously found somewhere like Olduvai Gorge, had lived a few hundred thousand years earlier.

So we had no impact on climate. The current fear-mongering is made completely out of the context of the earths history. Recent history.

NASA starts all their time series in the middle of the ice age. So yeah, todays readings on temperature and CO2 and whatever will look pretty amazingly dangerous by comparison with those readings. But thats because of where you start your data.

Intellectual malfeasance.

Chris Norman
April 16, 2023 7:02 pm

The growth in Arctic ice, coincident with the reducing Solar Cycles, 
The annual maximum extent in millions of square kilometres. 
Year, area, date. 
Source: the NSIDC.
2017…………………..14.43……..March 7    
2018……up to…….. 14.48……..March 17
2019……up to……… 14.78……..March 3
2020……up to……… 15.05……..March 5 
2021…down to…….. 14.77……..March 21
2022….up to…………..14.88………Feb 25

Chris Norman
April 16, 2023 10:43 pm

And the max for 2023 is March 6th at 14.62.
Obviously the NSIDC teaming up with NASA Giss is beginning to kick in.

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