Hudson Bay sea ice update: many polar bears are still on low concentration ice offshore

Almost half of all tagged Western Hudson polar bears are still out on the ice of Hudson Bay, even though much of it is broken up in pieces: as of yesterday, 10 out of 22 bears were still offshore.

Mother and cub near Churchill last year, 30 October 2021.

This is shaping up to be a great year for Hudson Bay bears!

It also appears none of the bears onshore are causing problems in Churchill, as the Polar Bear Alert Program weekly reports for Churchill have not yet begun. Last year the first report was issued for the first week of July, while in 2020 the first report didn’t come out until the end of August.

Sea Ice Charts

For the first week of August 2022.

Weekly chart for 1 August 2022 by stage of development (i.e. thickness):

Daily charts for 4 August 2022 by concentration (below), Northern and Southern Hudson Bay (note all of this ice, as in the chart above, is first year ice >1.2m thick):

Tracking polar bears with collars

According to Andrew Derocher (3 August), who installed the tracking devices on these 22 bears:

Some W. Hudson Bay polar bears hanging out on the last sea ice. It’s been too cloudy to get a good ice image but there’s precious little left. August ashore is a great year for the bears!

Note that the ice charts Derocher uses show only ice >50% concentration, which at this time of year leaves out a lot of polar bear habitat. Some bears are staying out on the ice as long as physically possible while a few others at the same latitude headed to shore much earlier: clearly, there is some aspect of individual preference regarding when bears decide to head ashore and is not all based on some set-in-stone threshold of ice concentration as polar bear specialists would have you believe.

Compare the charts above to Derocher’s chart below: what looks like bears on open water north and south of Churchill are actually tagged bears on low concentration sea ice (which is probably used by even more untagged bears):

via polarbearscience

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August 4, 2022 at 09:54PM

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