Tag Archives: variation

Now 20 years with no trend in ice breakup dates for Western Hudson Bay polar bears

Straight from the horse’s mouth: all polar bear females tagged by researchers around Churchill in Western Hudson Bay last year were still on the ice as of 25 June. With plenty of ice still remaining over the bay, spring breakup will be no earlier this year than it has been since 1999. Contrary to predictions of ever-declining ice cover, the lack of a trend in sea ice breakup dates for Western Hudson Bay is now twenty years long (a hiatus, if you will) and yet these bears are repeatedly claimed to have been seriously harmed in recent years by a loss of sea ice.

Derocher 2019 WHB collared females 25 June all bears still on the ice

In fact, WH bears have faced relatively few ‘early’ years of sea ice breakup and breakup has never come before the 15th of June. The earliest recent spring breakup date did not come in 2012 – when sea ice hit a summer record low – but in 1999, when Hudson Bay sea ice suddenly began to melt by late June rather than mid-July (Cherry et al. 2013; Castro de la Guardia et al. 2017; Lunn et al. 2016). And this year, as has been the case since 1999, breakup looks to be about two weeks later (give or take a week or so, at around 1 July), than was the case in the 1980s and early 1990s.

In other words, there has been no escalation of breakup dates since 1999: there has been no declining trend in breakup dates for Western Hudson Bay polar bears for 20 years (and no trend in fall freeze-up dates either).

UPDATE 26 June 2019: Here is the latest sea ice chart for the week of 24 June 2019 from the Canadian Ice Service (all that dark green is thick first year ice >1 m thick):

Hudson Bay weekly stage of development 2019 June 24
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USGS promotes another flawed polar bear model: GHG emissions still “primary threat”

It’s still based on the same flawed ecological premise as all previous models – it assumes that sea ice was a naturally stable habitat until human-caused global warming came along. It also uses slight-of-hand maneuvers to correlate declining summer sea ice and declining polar bear population numbers.

PolarBearCV1_USGS_2009

Just because they keep repeating the same hype doesn’t make it true.
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Arctic sea ice extent total for March does not equal global polar bear habitat

Only half or less of the estimated 2.6% loss per decade of March sea ice extent since 1979 (Fig. 1, below) represents a decline in polar habitat. That’s because several regions with sea ice that are not home to polar bears, like the Sea of Okhotsk, are included in Arctic sea ice totals.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015, which includes ice in the Sea of Okhotsk and the Sea of Japan, a decline of 2.6% per decade. NSIDC, March summary 2015.

Figure 1. Average monthly Arctic sea ice extent for March 1979-2015 (which includes ice in the Sea of Okhotsk, the Sea of Japan, and the Baltic, where polar bears do not live), shows a decline of 2.6% per decade. NSIDC, March summary 2015.

Both the Sea of Okhotsk and northern Sea of Japan (Fig. 2) have sea ice in winter (which is included in total Arctic sea ice records) but they are not truly “Arctic” – neither is connected to the Arctic by continuous ice, even when the ice is at its maximum extent (nor is the Baltic Sea — in contrast to Hudson Bay and the east coast of North America, which are connected to the Arctic by continuous ice).

Sea of Okhotsk_1979 March marked_PolarBearScience

Figure 2. Location of the Sea of Okhotsk and Sea of Japan. Insert ice map for March 1979 from NSIDC shows it’s position relative to the Arctic proper.

That lack of connection to Arctic pack ice is probably the main reason that polar bears never colonized the Sea of Okhotsk, even though western Arctic seal species (ringed, bearded, spotted, and ribbon) and Arctic whales  (bowhead and beluga) live there. Polar bears don’t currently live in the Sea of Okhotsk and all evidence suggests they never have.

Sea ice maps show that about half of the total ice extent difference between March 1979 and March 2015 was due to a relatively large decline in sea ice cover for Sea of Okhotsk and northern Sea of Japan — regions without polar bears. Surely no reputable scientist or journalist would suggest that the “record low” maximum ice extent for 2015 has any relevance for polar bear health and survival? [or for Northwest Passage travel, for that matter] Sadly, they would.

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