Hudson Bay sea ice loss has not accelerated since 2014: in fact, summer ice cover has improved

This is an early breakup year for Hudson Bay but sea ice loss has not been accelerating. While some Western Hudson Bay bears have been on land for weeks, others are still out on melting remnants of sea ice, much of it invisible to satellites. This is only the third year since 2014 that the bay has had less than usual amounts of ice, which means most years since then have had normal or nearly normal ice coverage, similar to the 1980s. Hardly the ever-worsening catastrophe of sea ice loss story being spun in the media for Western Hudson Bay polar bears.

From the tracking map above, out of the 38 visible tags or collars on bears at 11 July 2023, 16 bears (42%) were on land and 22 (58%) were still out on the sea ice. That’s virtually identical to the 40/60 percent split last week when there was even more ice.

Ice coverage this week

For the week of 10 July 2023, this ice chart from the Canadian Ice Service (below) suggests that at least four tagged bears (see chart above) are resting on ice that the satellites can’t see. It’s unlikely they are swimming because they were in similar locations last week. This is an earlier-than-usual breakup pattern, similar to what was documented for the two decades after the step-change in 1995.

Polar bears and sea ice

NASA Earth Observatory recently (12 July 2023) provided a bullhorn for activist polar bear specialists to advance their scary narrative about Hudson Bay polar bears (my bold):

In 2023, some Western Hudson Bay polar bears started to return to shore in mid-June, but others lingered on the ice well into July. “Mid-June is early to have bears on land,” said University of Alberta scientist Andrew Derocher. “When I started studying polar bears in Western Hudson Bay in the 1980s, we would have bears on the ice well into August.”

…

Despite some of the bears swimming ashore early, Derocher noted that many bears were still out on the ice in early July, despite how little ice was left and how fragmented the last bits of ice had become.

“The bears on ice are hanging on at extraordinarily low ice levels,” Derocher said. “But better for them to be there trying to kill another seal than on land with little or nothing to eat. Bears can feed and keep putting on weight well into the summer if they have the ice. For polar bears, it truly is survival of the fattest.”

Funny that Derocher doesn’t mention that polar bears were out on the ice well into August in both 2020 and 2022: no, he leaves that part out and emphasizes that breakup is early this year.

Do polar bears in Hudson Bay kill seals in July and August

Also, despite Derocher’s statement to NASA, there is no documented evidence that western or southern Hudson Bay polar bears routinely kill seals from melting sea ice in July and August. Derocher assumes they do but he has no evidence that this actually happens because no one has ever studied this phenomenon. It’s unlikely that more than a few seals spend extented periods hauled out on sea ice in mid-summer because most of them, including adults and juveniles, will be out in open water feeding.

What’s normal breakup for Hudson Bay?

The diagram below is from a paper by Ian Stirling and colleagues (2004), and it shows what the usual or normal pattern of sea ice breakup was between 1971 and 2000. Ice conditions this year are about what was expected in late July or about two weeks early (dark grey). According to the analysis by Castro de la Guardia and colleagues (2017), breakup in 2015 was about two weeks earlier than it had been prior to 1995 or similar to this year.

Mid-July ice cover 2015-2023

However, the pattern this year is unusual compared to the last nine years. Since 2014, only 3 years out of 9 (2023, 2021 and 2017) had less than usual amounts of ice at mid-July. Four years (2016, 2019, 2020, and 2022) presented conditions that would be considered “normal” based on Stirling et al.’s long-term data (1971-2000), while 2015 and 2018 had lots of ice at mid-July but more of it than usual was in the northeast quadrant.

In other words, Hudson Bay has had normal sea ice cover at mid-July more often than it has had reduced ice cover. This means sea ice loss over the Bay has not been accelerating, rather ice coverage has been improving overall since 2014 compared to the two decades before. That’s why the claimed 27% decline in polar bear numbers for Western Hudson Bay between 2017 and 2021 could not be blamed on lack of sea ice: sea ice conditions were mostly been very good in those years.

Have a look at the ice charts below, starting with this year:

References

Castro de la Guardia, L.., Myers, P.G., Derocher, A.E., et al. 2017. Sea ice cycle in western Hudson Bay, Canada, from a polar bear perspective. Marine Ecology Progress Series 564: 225–233. http://www.int-res.com/abstracts/meps/v564/p225-233/

Stirling, I., Lunn, N.J., Iacozza, J. et al. 2004. Polar bear distribution and abundance on the southwestern Hudson Bay coast during open water season, in relation to population trends and annual ice patterns. Arctic 57(1):15-26. https://journalhosting.ucalgary.ca/index.php/arctic/article/view/63539 Open access.