New Data Shows Svalbard Polar Bears Are Fatter Than They Were in 1993 Even though Low Sea Ice Continues – Are You Up to Speed With That?
Researchers in Norwegian Polar Institute finally updated their spring data, showing that male polar bears are even fatter in 2024 than in 1993, and the number of new cubs is just as high, despite sea ice continuing at low levels. low in the region, especially during the summer months.
Area
The area surveyed in August 2015 where polar bears were found, as shown below (Aars et al. 2017) included the northern Svalbard ice sheet. The spring surveys carried out in March/April appear to have only covered the mainland areas of the Svalbard archipelago.
Sea ice conditions
This year, at the end of May around Svalbard:
In the wider area of the Barents Sea:
Unfortunately, Norwegian Ice Authority data only goes back to 1997, so we can’t know specifically what conditions were like in 1993, but other sources show more extensive sea ice in all seasons .
Hopen Island, circled on the map below, is so far south that bears could only roost there when icefall in the Barents Sea spread (Andersen et al. 2012; Derocher et al. 2011).
Chart below, Copied from polar bear MOSJ website, showing the number of days from 1979-2024 when sea ice covered the surrounding area Hopen Island in the fall (October 1 – December 31) exceeds 60%. In the early 1990s, the ice surrounding Hopen was unusually dense (black line). By 1994, many female bears were using the island for breeding grounds (top of the blue line) but after 2007, few bears did so due to lack of sea ice.
Spring 2024 data
Norway’s latest data shows lion cub recruitment (the number of cubs in a litter), reproduced below, at its highest ever in 2024 and as high as 1993 before sea ice began to decline, although by 2023 the figure had decreased. lowest since 1993.
Data on the body condition of male bears in spring (March-May, reproduced below), monitored since 1993, show a slight decrease until 2000.
However, after 2000, the bear’s body condition increased over the next two decades until 2024 despite a significant reduction in sea ice cover, making the bear’s overall condition in 2024 is better than 1993 and any year since then.
Conclude
This 2024 data from male Svalbard bears mirrors data from female bears captured up to 2017, showing a similar pattern (Lippold et al. 2019): less sea ice in recent years This means bears are in better shape than they were in the 1990s when there was more sea ice.
Lippold and colleagues (2019: 988) have stated this clearly for female polar bears (I bolded]:
“Unexpectedly, the body condition of female polar bears in the Barents Sea increased after 2005, even though the sea ice receded after 2005. ∼50% since the late 1990s in the region, and the length of the ice-free season increased by more than 20 weeks from 1979 to 2013. These changes are also accompanied by winter ice melt, which is especially pronounced in the Barents Sea compared to other Arctic regions. Despite the decreasing amount of sea ice in the Barents Sea, polar bears may not lack for food as long as there is sea ice during their peak feeding period. Polar bears feed heavily from April to June when ringed seals give birth and are particularly vulnerable to predation, while predation rates during the rest of the year may be low.”
As I explained before, this is almost certainly caused by the fact that there is less sea ice in the summer. increase primary productivityy — more plankton feeds more fish, which in turn feeds more seals — which creates plenty of seals for polar bears to feed on when there is sea ice in the spring (Crockford 2023; Frey and al 2022).
Norwegian authors conclude their 2024 polar bear report by stating [my bold]:
Although sea ice loss has been recorded around Svalbard in recent years and is expected to continue in the coming decades, the size of the subpopulation is likely to remain below carrying capacity. contain.
It is therefore possible that the current subpopulation is still growing, or at least stable, even though available habitat has become poorer for much of the year. …
Observations to date cannot demonstrate that changes in climate have had a clear impact on the subpopulation.
Presenter
Aars, J., Marques, T.A., Lone, K., Anderson, M., Wiig, Ø., Fløystad, IMB, Hagen, SB and Buckland, ST 2017. 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 bears (Ursus maritimus) distributes maternity wards in Svalbard, Norway. Polar biology 35:499-508.
Crockford, S.J. 2024. State of the Polar Bear 2023. Summary report 67. Global Warming Policy Foundation, London. Download PDF This.
Derocher, A.E., Andersen, M., Wiig, Ø., Aars, J. and Biuw, M. 2011. Sea ice and polar bear den ecosystem on Hopen Island, Svalbard. Marine ecological process chain 441:273-279.
Frey, KE, Comiso, JC, Cooper, LW, et al. 2022. Primary productivity of the Arctic Ocean: seaweed responses to climate warming and sea ice decline. 2020 Arctic Report Card. NOAA. DOI: 10.25923/Oje1-te61 https://arctic.noaa.gov/Report-Card/Report-Card-2022/Arctic-Ocean-Primary-Productivity-The-Response-of-Marine-Algae-to-Climate-Warming-and-Sea-Ice- Depression
Lippold, A., Bourgeon, S., Aars, J., Andersen, M., Polder, A., Lyche, J.L., Bytingsvik, J., Jenssen, B.M., Derocher, A.E., Welker, J.M., and Routti, H. 2019. Temporal trends of persistent organic pollutants in Barents Sea polar bears (Ursus maritimus) related to changes in eating habits and body condition. Environmental Science and Technologymedicine 53(2):984-995. Take paper This.
Related
