Tag Archives: tagged bears

Early sea ice breakup in W Hudson Bay caused by “record breaking” warmth in 2023 but not 2015?

According to Polar Bears International, the “3rd-earliest” breakup date for Western Hudson Bay was caused by a “record breaking” heat wave in May. Western Hudson Bay sea ice hit the 30% coverage threshold used by PBI to define “breakup” on 17 June this year, prompting speculation about potential future impacts on polar bear survival should breakup come even earlier.

This year’s break-up date of June 17 is the 3rd earliest in the 45 years of satellite-based sea ice data from Western Hudson Bay, after 2015 and 2003.” [Flavio Lehner, PBI]

17 June 2023 is day 168 on the Julian calendar used to graph the data in the image included in the PBI essay (see copy below). However, the data point for 2003 is about three days earlier, on day 166 (14 June) and the point for 2015 is on day 152 (1 June).

If “record-breaking” heat caused this year’s early ice retreat, what caused the ice to retreat more than two weeks earlier in 2015? May was warm that year along the west coast as well but obviously not “record-breaking” warmth, because the records were broken this year. In fact, whatever warmth that occurred only affected ice melt in the western sector, while very thick ice over the rest of the bay resisted melt and allowed bears to stay out many weeks later than usual.

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Not predicted: more sea ice than average in southern-most Arctic first week of August

Polar bear habitat update for the first week of August 2019 shows there is still more sea ice than average in Hudson Bay, the southern-most area of continuous habitation for this species. That certainly wasn’t part of the predictions of doom, especially since freeze-up in that region for the last two years has also been earlier-than-average which means a shorter ice-free season than we’ve seen for decades.

Hudson Bay weekly departure from normal 2019 Aug 5

Despite ice coverage for the Arctic ice as a whole being marginally lower than it has been since 1979 for this time of year, sea ice for the first week of August was also above average around Svalbard in the Barents Sea and higher than the last few years in the Central Arctic, which is a critical summer refugium for polar bears that live in the peripheral seas of the Arctic Ocean, including the Chukchi (see photo below, taken in early August 2018).

Chukchi Sea polar bear Arctic_early August 2018_A Khan NSIDC small

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