Western Hudson Bay sea ice breakup for polar bears like the 1980s for 3 of the last 5 yrs – Watts Up With That?

From Polar Bear Science

Susan Crockford

The 1980s and early 1990s are said to have been the “good old days” for sea ice conditions and polar bears in Western Hudson Bay, with all tagged bears usually ashore by mid-to-late August. Then an abrupt step-change in sea ice breakup dates brought polar bears to shore an average of two weeks earlier in the late 1990s. From then until 2019, the only significant outlier to all tagged bears being ashore by about late July was 2009, which was such an unusually cold year that the last bears came ashore about August 20.

That pattern changed in 2020, when the last bears came off the ice as late as they had in 2009, on August 21. Something similar happened in 2022, when the last bears came off a small remnant of ice even later, about August 26. And this year, the bears may be moving ashore even later: there is even more ice remaining off WH and much of it is thick compacted ice that hasn’t melted much over the last few weeks, which means bears have been as late onshore as the 1980s for three out of the last five years.

About 40% of all tagged bears were still offshore at August 8. Below, chart showing position of tagged polar bears at August 8 (11/27 or 41% are still on the ice):

Two years ago, at August 7, 2022 (below), there appeared to be barely any ice off WH but we know that satellites notoriously under-report ice by up to 20% during the melt season because they misclassify melt-ponds over ice as open water. Still, the last tagged bears stayed offshore another two weeks in 2022 on whatever bits of ice remained, like they did in the 1980s when there was more ice available:

This year the situation is even more unusual. Against all predictions of deteriorating summer sea ice conditions, there is a large patch of thick to very thick sea ice off W. Hudson Bay. Below, see the daily sea ice stage of development chart (i.e. thickness) for August 10: W. Hudson Bay has much more ice this year than 2022, and there could be even more misclassified as open water:

Polar bear specialist Andrew Derocher dutifully reported the unexpected tagged polar bear/sea ice situation in WH last week but failed to mention that this is the third time in five years that bears have been offshore the first week in August as they were in the 1980s even as he acknowledges that this phenomenon should be good news for bear survival.

In my opinion, 40% of all tagged bears being offshore is what I would call more than “some.” So many bears offshore and the current ice conditions suggest it’s possible that more than one or two bears might remain on that large block of thick ice until very late August or even early September, which might be the first time that’s happened since the 1980s (if it even happened then).

For comparison, in 2022, at August 5, 33% of tagged bears (8/24) were still out on small patches of ice that satellites were obviously under-reported because (given that some bears appear to be on no ice whatsoever):

Even with some bears onshore, there has not yet been a problem bear report issued by the town of Churchill for 2024. In 2020, the first problem bear report (for the last week of August) was not released until September 1, so we may have to wait a few weeks more to find out the situation there.