In Churchill, every year polar bears gather on the shores of Hudson Bay to wait for the big freeze, and every year they’re waiting longer.
This was the exact statement at seven minutes into the BBC’s Arctic Live programme last night. This was immediately followed up with the comment, “But the prospect of a future without them is impossible to imagine”.
This unsurprisingly set the scene for the rest of that segment of the programme. The Arctic is warming, ice is melting and polar bears are endangered.
As I showed yesterday, there is no truth in the claim at all.
But let’s look at one more graph, this time the week by week ice coverage for Hudson Bay in 2015, as presented by the Canadian Ice Service:
It starts at the beginning of October, and runs to the end of December. As can be seen, the refreeze, which began in the last week of October, occurred just when it would be expected to. During November, ice coverage was, if anything, above average.
Arctic mammal expert, Dr Susan Crockford, actually addressed this issue three years ago:
This is a follow-up to an earlier post, Polar bear problems in N Hudson Bay not due to late freeze-up, to counter some misinformation that’s being circulated about the history of Hudson Bay freeze-up dates.
Polar bear biologists working in Western Hudson Bay published new definitions of breakup and freeze-up earlier this year. The new method better reflects how polar bears interact with seasonal changes in sea ice on the bay.
Formerly, 50% ice coverage levels were used to assign the date when major ice change phenomena were reached each year (breakup in summer, freeze-up in fall (e.g. Gagnon and Gough 2005). The new method (Cherry et al. 2013, see discussion here) defines breakup at 30% ice coverage and freeze-up at 10%.
Cherry and colleagues had a fairly complicated method of defining 30% coverage for breakup in Western Hudson Bay. However, freeze-up in the fall is much simpler because ice always forms first along the western shore, starting in the north.
This means that the weekly graphs of ice development provided by the Canadian Ice Service for Hudson Bay, which are expressed as a percentage (just like the Cherry et al. study), can be used to compare freeze-up dates historically.
These graphs refute the absurd claim that freeze-up on Hudson Bay has been “one day later each year” over the last 30 years – an assertion repeated just the other day at PBI.
If we use the 10% threshold, we can see that this arrived in the second week of November last year, exactly when the 1981-2010 median was.
Looking at this week for each year back to 1994, there is no obvious trend, and certainly no evidence to back up the BBC’s claim.
We can do one more test. Using the Canadian Ice Service data again, I have plotted the week when sea ice concentration passed above the 10% threshold, for each year since 1994. (Week 46 is November 12th).
As you can see, the refreeze occurred in week 47 for most of the years. Two years, 1998 and 2010, had the latest dates, whilst 1995, 2000, 2004 and 2015 had the earliest. It is clearly not the case that every year polar bears gather on the shores of Hudson Bay to wait for the big freeze, and every year they’re waiting longer.
I will be firing off a complaint to the BBC tonight.
Apparently the next episode in the series will look at “climatological changes taking place in the Arctic”. No doubt, this will also myths and prejudice, rather than actual facts.
Source: NOT A LOT OF PEOPLE KNOW THAT
