Posted on August 29, 2019
Sea ice melt in the Arctic Basin leaves an area for polar bears larger than Greenland
Most polar bears that spend the spring feeding in the peripheral seas of the Arctic Basin (such as the Beaufort, Chukchi, Kara, and Barents Seas) remain on the persistent pack ice of the central Arctic during the summer and this August, that refugium is still larger than Greenland. Most of these bears do not use this July-September Arctic Basin ice as a hunting platform unless they are very lucky: the few seals available are hard to catch. For the most part, polar bears fast or eat very little during the summer whether they are on land or on ice (see references in this post).
Since early June, sea ice experts have been wringing their hands over the melting of Arctic sea ice and offering breathless speculation that this year’s September minimum could be – gasp! – as low as or less than 2012 or even less. But now, as the graph of ice cover at 28 August shows below, that outcome is looking not just unlikely but virtually impossible (the blue line is 2019 extent, red dashed line is 2012, and the brown line is 2016):
As expected, the failure of the ice to remain on track to set a new record September low due to global warming is shrugged off with a reminder that summer ice extent “is sensitive to changes in daily weather conditions.”
According to NSIDC Masie ice charts shown below, there is exactly the same amount of ice in the Arctic Basin this year at the end of August – 3.0 mkm2 – as there was in 2012: it was just distributed a little differently. This makes the usual summer refugium for many polar bears larger in area than all of Greenland, which is only about 2.17 mkm2. That’s plenty of space for thousands of bears to hang out for a few months.
Sea ice in the Arctic Basin at 26 August 2019 (3.0 mkm2):
Sea ice in the Arctic Basin at 26 August 2012 (3.0 mkm2):
At 26 August 2019, sea ice was still present in the peripheral seas: packed into the Canadian Arctic Archipelago, off northeast Greenland and the northern Barents Sea as well as the northern Laptev Sea. This is lots of ice for summering polar bears:
Barents Sea and Svalbard
In 2012, the Barents Sea was totally ice-free by late July yet when the Svalbard polar bear population survey was completed in August 2015, the population had grown by 42% – this was apparently a non-statistically significant increase but definitely not a decline. Ongoing research shows Svalbard bears are still thriving.
The low sea ice coverage in the western Arctic since early summer this year has been more than balanced out by the abundance of ice in the eastern Arctic: ice loss in the Beaufort and Chukchi Seas early in the season was the Barents Sea’s gain.
Barents Sea polar bears now have ice close to shore this summer but it remains to be seen if this will garner any advantage to their health and survival compared to previous years.
Last year at the beginning of August (above), there was no ice anywhere near Svalbard but this year just days from the end of August (below) the northeast portion of Svalbard is surrounded by ice that’s 2 metres thick! However, polar bears don’t need thick ice: half a metre of ice (i.e. 50 cm) is more than enough to support a full grown bear. We know this because in the fall, bears on land head out on ice when it’s about 30 cm thick.
Svalbard ice extent this year is much higher than average:
Sea ice at Svalbard, 26 August 2019:
Compare above to 27 August 2012 (below):
Polar bear specialist Andrew Derocher claims that lots of ice this year around Svalbard is good news for polar bears but the evidence from previous years shows that no ice around Svalbard at the height of summer has not been detrimental to their health and survival (Aars 2018; Aars et al. 2017; Andersen et al. 2012; Crockford 2019a, b).
Canadian Arctic Archipelago
Even more than a week earlier in 2012 (below, the only image I have is 19 Aug) the ice was mostly clear through the eastern approach to the northern route of the Northwest Passage. By the end of August, one small boat had made it through that tricky northern passage, which looks highly unlikely to be possible this year for vessels other than icebreakers.
Here is a satellite image of the route published by NASA on 2 August 2012, but note this caveat:
“According to reports from the Canadian Ice Service, ice appeared to retreat quickly from Parry Channel in late July and early August 2012, but the channel was probably not entirely open. In some cases, sea ice can be thin enough to escape detection by a satellite sensor, but still be thick enough to hamper navigation.”
Northwest Passage routes:
The fact that the Royal Canadian Mounted Police schooner St. Roch was able to transit the northern passage in the summer of 1944 from east to west, encountering little ice for much of the middle portion of the journey, is evidence that ice-free conditions in Parry Channel occurred naturally even before global warming. A detailed account of the St. Roch voyages (a fascinating read with a map and lots of pictures, from Canadian Geographic 1945) is available here in pdf format.
Aars, J. 2018. Population changes in polar bears: protected, but quickly losing habitat. Fram Forum Newsletter 2018. Fram Centre, Tromso. Download pdf here (32 mb).
Aars, J., Marques,T.A, Lone, K., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The number and distribution of polar bears in the western Barents Sea. Polar Research 36:1. 1374125. doi:10.1080/17518369.2017.1374125
Andersen, M., Derocher, A.E., Wiig, Ø. and Aars, J. 2012. Polar bear (Ursus maritimus) maternity den distribution in Svalbard, Norway. Polar Biology 35:499-508.
Crockford, S.J. 2019a. State of the Polar Bear Report 2018. Global Warming Policy Foundation Report 32, London. pdf here.