Dr. Susan Crockford
Sea ice is well above recent levels for this time of year in the Southern Beaufort and only time will tell if that’s bad news for polar bears. Seals need the open water that early summer polynyas provide in order to feed and some polar bears make use of the hunting opportunities (Stirling and Cleator 1981; Stirling et al. 1981).
It’s been a decade since there was this little open water at the beginning of summer in the western North American Arctic, especially the Southern Beaufort. It’s looking unlikely there will be extensive open water until well into July, which may result in many fewer bears on shore in early summer. Recall that in July 2019, NOAA employees counted 31 fat, healthy bears onshore along the Alaska coast.
Past and Present conditions
The Cape Bathurst polynya in the Eastern Beaufort Sea west of Banks Island was usually prominent in May during the late 1970s (images below from Smith and Rigby 1981):
As you can see, this polynya was present in classic formation at May 15 this year:
However, by early June it had almost entirely re-frozen:
Now, at the first day of summer, the polynya is only just starting to open back up again and the ice surrounding it is thick multiyear ice (brown) and thick first year ice >1.2m (dark green):
The chart below shows there is more ice than usual in the Eastern Beaufort (blue):
The classic CIS chart shows what this looks like as ice coverage vs. open water:
Compare the above chart for this year (above) to previous years (below).
On or about the same date going back in time shows how unusual this situation is: there hasn’t been this little open water since 2013.
Stirling, I. and Cleator, H. (eds). 1981. Polynyas in the Canadian Arctic. Canadian Wildlife Service, Occasional Paper No. 45. Ottawa.
Smith, M. and Rigby, B. 1981. Distribution of polynyas in the Canadian Arctic. In: Polynyas in the Canadian Arctic, Stirling, I. and Cleator, H. (eds), pg. 7-28. Canadian Wildlife Service, Occasional Paper No. 45. Ottawa.
Stirling, I, Cleator, H. and Smith, T.G. 1981. Marine mammals. In: Polynyas in the Canadian Arctic, Stirling, I. and Cleator, H. (eds), pg. 45-58. Canadian Wildlife Service, Occasional Paper No. 45. Ottawa. Pdf of pertinent excerpts of above papers here.