By Polar Bear Science
Dr. Susan Crockford
Areas of open water or thin ice in the spring are essential for the survival of arctic species, as I have emphasized in my recent peer-reviewed article on polar bear ecology. Sea ice remains abundant in spring (April to June), which is an important feeding period for polar bears: they must consume about two-thirds of their total calories for the year. Most of those calories come from newborn seals (brim, beardand harp).
In southern areas, such as Hudson Bay and Davis Strait, almost all of this feeding is completed by the end of May, making June a opportunistic hunting time for most bears. : if they find the seal, they will kill and eat it but if not, they can do without. It’s not just my opinion but the reason given by polar bear expert to explain why polar bear populations in the southern Hudson Bay did not refuse in the 2000s despite the sudden increase in the ice-free season:
…Although parting has lasted up to three to four weeks in parts of Hudson Bay, it still occurs no earlier than late June or early July, thus not affecting the brood’s chances of feeding. Neonatal annular seals are born in March-April east of Hudson Bay. Thus, losing a few days or weeks of hunting opportunities during June and July will deprive adult seals of the opportunity to forage, but not the crucial period of spring when they really are. hyperphagic. [Obbard et al. 2016:29]
Polynyas around the world
From my paper, unlabelled (Crockford 2022, open access). Some polynyas, like the vast area off the coast of Siberia, are not actually open water but areas of thin ice that seals and bears can penetrate easily. As a result, they are often difficult to detect on sea ice charts.
Sea ice in mid-May
Canada (May 15, 2022)
Arctic in general (May 15, 2022)
Close-up by area May 13, 2022
Bering / Chukchi / Beaufort (May 13, 2022)
Barents / Kara Sea (May 13, 2022)
Canada’s East Coast / Western Greenland (May 13, 2022)
Presenter
Crockford, SJ 2022. Polar bear fossils and archaeological records from the Pleistocene and Holocene relate to sea ice levels and open water polynyas. Open Quaternary 8 (7): 1-26. https://doi.org.10.5334/oq.107
Obbard, ME, Cattet, MRI, Howe, EJ, Middel, KR, Newton, EJ, Kolenosky, GB, Abraham, KF and Greenwood, CJ 2016. Body condition trends in polar bears (Ursus maritimus) from the South Hudson Bay subpopulation associated with sea ice changes. Arctic Science 2 (1): 15-32. https://doi.org/10.1139/as-2015-0027
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