Svalbard Norway now has extra polar bear habitat than it did 20 years in the past

From Polar Bear Science

Posted on March 1, 2020 | 

Sea ice round Svalbard, Norway on the finish of February 2020 is means above common, because the graph beneath reveals – with extra polar bear habitat now than there was in 20 years.

Some comparability charts beneath present that the graph above contains some very excessive ice years within the 1980s (reaching that dotted line above the imply) for which solely international charts can be found.

Nevertheless, opposite to solutions that extra Svalbard ice is healthier for polar bears, there isn’t a proof that low extent of sea ice habitat in winter or summer time during the last 20 years harmed polar bear well being, reproductive efficiency, or abundance. Actually, polar bear numbers in 2015 have been 42% larger than they have been in 2004 (though not a major improve, statistically talking) and most bears have been discovered to be in glorious situation.

This implies a return to extra intensive ice to the Svalbard area in winter could have little affect on the well being of all the Barents Sea subpopulation, though it’d change the place pregnant females are capable of make their maternity dens if ice kinds early sufficient within the fall. In different phrases, the inhabitants ought to proceed to develop because it has been doing because the bears have been protected by worldwide treaty in 1973.

After substantial thick ice endured into July final summer time, at 28 February 2020 Svalbard is nearly surrounded by ice, as is Bear Island to the south (that little patch of gray on the backside, encompass by inexperienced and yellow) – the presence of pack ice invariably brings polar bears to Bear Island. There’s substantial ice off the west coast (giving polar bears quick access to settlements there) and really shut drift ice (purple, 9/10-10/10 protection) is dominant at each north and south ends, which was not true even twenty years in the past, as I present beneath:

At 2019 for a similar date, the ice was not fairly as intensive or as concentrated, with open water between Spitzbergen and Nordaustlandet:

2017 was very odd, with a giant patch of open water to the northeast of Nordaustlandet (the primary and solely time this has occurred in winter, so far as I do know):

In 2014, so little ice reached south of Svalbard that Bear Island is left off the chart, which was additionally true again to 2008 (however the island got here again to the maps in 2017):

The yr with something near the quantity of ice as this yr, at this date, within the Norwegian Ice Service document (which solely goes again to 1997) was twenty years in the past, within the yr 2000 (see chart beneath). On the finish of February 2000, Svalbard was fully surrounded by ice, with a thick band of ice off the west coast and far ice to the south, though the ‘tongue’ of open water extending north of Spitzbergen that has been attribute of situations for the final 20 years was already current:

See 2020 beneath once more for comparability with 2000 above. Discover that in 2000 the ice didn’t attain Bear Island and there was not almost as a lot “very shut drift ice’ as this yr (cross-hatched within the chart above, purple within the 2020 chart beneath), particularly to the north and south of Spitzbergen. This yr, that distinguished ‘tongue’ of open water north of Spitzbergen is gone and there may be extremely concentrated ice between Spitzbergen and the big northeastern island of Nordaustlandet. Additionally, in 2020 the ice extends to this point south it runs off the underside of the chart past Bear Island:

By 2001 (beneath), a change within the sample of sea ice in the course of the winter that had been the norm within the 1980s and 1990s (mentioned beneath) set in. From 2001 onward, there was much less ice than ordinary by the top of February and/or much less concentrated ice, particularly on the west coast and north of Spitzbergen. Whereas this yr’s sample is a stark reversal of that pattern, it will likely be a couple of years earlier than we are able to inform if that is one other shift or simply yearly variation.

For the interval 1979-2020, polar bear habitat round Svalbard presently of yr was in all probability at its most intensive in 1979, because the NSIDC chart for February reveals (beneath, the place the magenta line is the 1981-2010 imply), even whereas ice within the Bering Sea was beneath common (extra on that in one other submit):

Within the 1980s, Svalbard ice diversified up and down however typically above the long-term imply (see 1986 beneath, for instance):

Polar bear well being and copy values are solely accessible in detailed kind again to 1993 however there may be not a lot distinction between the 1990s and the 2010s (see graphs beneath, but in addition see Larsen 1972; Wiig 1998). The variety of females with one yr previous cubs (mortality is all the time highest within the first few months and these surveys are performed in April, simply after moms with new cubs emerge from their delivery dens) has not modified:

Nor has the burden of grownup males modified over this era:

What has modified is the variety of females capable of make dens on the islands of the west coast of Svalbard (see graph beneath).

Most polar bear females that after routinely made their maternity dens on the japanese islands of the Svalbard archipelago (see map beneath) now den on the ocean ice to the east and north of Svalbard, on the ice across the archipelago of Franz Josef Land, or on the islands of Franz Josef Land itself (Aars 2015, 2018; Aars et al. 2009, 2017; Andersen et al. 2012).

Aars and colleagues discovered solely about 200-250 bears have been loyal to the instant Svalbard area in 2015 (Aars et al. 2017). Throughout 2004 inhabitants survey, Aars and colleagues (2009) discovered about 3 times extra bears within the Russian sector of the Barents Sea than round Svalbard (for a complete estimate of about Three,000 bears). This reality is the idea of my suggestion that the 2015 survey that was restricted to Svalbard (Aars et al. 2017) might plausibly be extrapolated to provide a inhabitants estimate for all the Barents Sea of about Three,750 at 2015 (Crockford 2017, 2019, 2020), nonetheless not a statistically important improve given the strategies used.

If Svalbard sea ice habitat continues to differ sooner or later because it has since 1979, there isn’t a motive that Barents Sea polar bear inhabitants development is not going to carry on going.

References

Aars, J. 2015. Analysis on polar bears at Norwegian Polar Institute. On-line seminar (‘webinar”), January 14. pdf right here.

Aars, J. 2018. Inhabitants modifications in polar bears: protected, however rapidly shedding habitat. Fram Discussion board Publication 2018. Fram Centre, Tromso. Obtain pdf right here (32 mb).

Aars, J., Marques, T.A., Buckland, S.T., Andersen, M., Belikov, S., Boltunov, A., et al. 2009. Estimating the Barents Sea polar bear subpopulation. Marine Mammal Science 25: 35-52.

Aars, J., Marques,T.A, Lone, Okay., Anderson, M., Wiig, Ø., Fløystad, I.M.B., Hagen, S.B. and Buckland, S.T. 2017. The quantity and distribution of polar bears within the western Barents Sea. Polar Analysis 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. 2017. Testing the speculation that routine sea ice protection of Three-5 mkm2 ends in a higher than 30% decline in inhabitants dimension of polar bears (Ursus maritimus). PeerJ Preprints 2 March 2017. Doi: 10.7287/peerj.preprints.2737v3 Open entry. https://doi.org/10.7287/peerj.preprints.2737v3

Crockford, S.J. 2019. The Polar Bear Disaster That By no means Occurred. World Warming Coverage Basis, London. Obtainable in paperback and book codecs.

Crockford, S.J. 2020. State of the Polar Bear Report 2019. World Warming Coverage Basis Report 39, London. pdf right here.

Larsen, T. 1972. Norwegian Polar Bear Hunt, Administration,and Analysis. Bears Their Biology and Administration 2: 159-164.

Wiig Ø. 1998. Survival and reproductive charges for the polar bears at Svalbard. Ursus 10:25–32.

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