I’ve been busy with work-related activities lately and will be for several more weeks. Until then…
Sea ice changes since March 15 [Update added May 10, see below]
Lots of ice everywhere – even in Hudson Bay. A bit less ice in the Barents Sea (north of Norway) than there was two months ago at the sea ice maximum March 15 (see Fig. 1 below compared to the extent at May 5 in Fig. 2: both from NSIDC). But there is still quite a bit around Svalbard – that group of islands between NE Greenland and NW Norway (see Fig. 3 below a MASIE image, where this situation is more apparent).
Polar bears are eating and mating at this time of year (early May being the tail-end of the season in most areas) – and right now, they have a huge, circumpolar ice platform for those activities.
1972 – a bit over 40 years ago. Seven years before we had reliable sea ice extent data from satellites and the year before the international agreement was signed by Arctic nations to protect polar bears from overhunting.
In 1972, a bear biologist by the name of Jack Lentfer was working for the Alaska Department of Fish and Game, stationed at the Naval Arctic Research Lab in Barrow. Lentfer was one of the founding delegates of the Polar Bear Specialist Group, where he represented US interests until 1981.
In the proceedings of the 1972 PBSG meeting (Lentfer 1972a), Lentfer stated the following in his report to the group:
“Long term warming and cooling trends occur in the Arctic and probably affect polar bear distribution and numbers. Climatic trends should be considered when assessing bear distributions and population data on a long term basis.” [my bold]
Warming and cooling, not just warming.
He also had a paper published that year (Lentfer 1972b), entitled “Polar bear: Sea ice relationships.” Forty years on, I thought it was worth having a look at what Lentfer told his fellow polar bear biologist colleagues back then. Continue reading
Posted in History, Sea ice habitat
Tagged climate, cooling trends, Lentfer, PBSG, Polar Bear Specialist Group, population trend, sea ice extent, summer ice minimum, warming trends, winter ice maximum
The authors of a new paper out in PLoS Genetics (Cahill et al. 2013, entitled “Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution”) propose to explain how and why the brown bears (aka grizzlies) of the ABC islands of southeast Alaska (Admiralty, Baranof, and Chicagof – see previous post here), got to be so genetically distinct from brown bears on the Alaska mainland and so surprisingly similar (genetically) to polar bears. The authors determined (using a model) that this genetic pattern could be explained by an ancient hybridization event resulting from female polar bears cavorting with male brown bears in SE Alaska.
I had some issues with the way the paper was promoted by some of the co-authors, which I dealt with separately here. More importantly, I found the scenario these geneticists offered to explain how hybridization might have occurred to be patently implausible. Geological and fossil evidence from SE Alaska largely refutes their scenario, although another explanation may be more tenable. It is not impossible, in my opinion, that hybridization occurred in SE Alaska during the last Ice Age, but if it did, it almost certainly did not happen the way Cahill and colleagues suggest.
Posted in Evolution
Tagged ABC bears, black bears, brown bears, Cahill, genetics, Haida Gwaii, hybridization, Jim Baichtal, last glacial maximum, polar bear evolution, Prince of Wales Island, ringed seals, SE Alaska, sea ice extent, Tim Heaton
On Monday, March 25, the National Snow and Ice Data Center (NSIDC) announced that March 15 2013 was likely the maximum extent reached this winter. Note that just a few days ago, I discussed the relationship between maximum extent of sea ice and the global distribution of polar bears around the Arctic (see March 20th post here).
NSIDC says: “Arctic sea ice extent on March 15 was 15.13 million square kilometers (5.84 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole.” Click to enlarge.
A new paper out in the journal PLoS Genetics proposes that a hybridization event between female polar bears and male brown bears (aka grizzlies) occurred in Southeast Alaska at the end of the last ice age. I’ll get to a discussion of the paper itself (coming in a day or two) but first I have a few things to say about the global warming hyperbole generated by the people promoting the paper. I found it simply mind-boggling.
While the paper itself (Cahill et al. 2013: “Genomic Evidence for Island Population Conversion Resolves Conflicting Theories of Polar Bear Evolution”) contains only one short phrase that could possibly be interpreted as linking the results to future scenarios of catastrophic global warming, some of the co-authors have made statements (for the press release and in media interviews) that spin the global warming mantra right over the top. Continue reading
Posted in Advocacy, Evolution, Sea ice habitat
Tagged ABC bears, Beth Shapiro, brown bears, Cahill, climate, Ed Green, global warming hype, hybridization, ice age, polar bear evolution, polar bear spin, sea ice extent, sea ice models
It’s like pulling teeth, getting up-to-date information on breakup dates of Hudson Bay sea ice. You’d think with the importance of this seasonal event to the polar bears of Hudson Bay (some of which, we’re told, face the most perilous future of all polar bears worldwide), we’d get a press release every summer alerting us to the precise date of sea ice breakup and the subsequent arrival of the bears onshore. I’m thinking of something similar to the dispatches we get from the National Snow and Ice Data Center (NSIDC) when Arctic sea ice reaches its yearly maximum (e.g. March 2012) and its yearly minimum extent (e.g. September 2012).
Sadly, this is not the case.
So I was intrigued to see that a new paper just out in the Journal of Animal Ecology, by Seth Cherry (a Ph.D. student of Andrew Derocher) and colleagues, dealt with Hudson Bay breakup dates. I was hoping for some data beyond 2007, which has been the limit of information provided so far by polar bear biologists (see previous posts here and here). Unfortunately, because the methods for determining breakup dates in this paper are so different from previous ones (more detail below), the new data (1991-2009) can’t be compared to earlier studies that go back to 1979. But there is some good news.
Although you wouldn’t know it by the author’s conclusion, the results of the study confirm for this region my previously stated contention that polar bears need spring and early summer ice (March through June) for gorging on young, fat seals and documented declines in sea ice have rarely impinged on that critical feeding period – by which I meant, bears have seldom, if ever, been forced off the ice of Hudson Bay as early as June.
The study also confirms that there has not been any kind of spectacular retreat of sea ice breakup dates – coming earlier and earlier in the season – over the last 19 years and that polar bears did not arrive on shore in 2009 until very late – approximately 22 August – the same date they came ashore in 1992.
Below are two figures from the paper: one (the map) necessary to understand the new “Cherry method” of calculating breakup dates for Hudson Bay (no disrespect intended) and the other (the graph), which presents the data collected. The table with my converted breakup dates is below them. A few quotes from the study and some comments on it follows.
UPDATE (March 21 2013; 6:12 PM PST). A typo in the table has been fixed (2001 is Jun 21 not Jul 21) and the post amended accordingly.
I’ve said it before but it’s worth saying again now that the sea ice in the Arctic is approaching its seasonal maximum extent and thickness: polar bears are limited by winter sea ice extent (Fig.1), not by the minimum extent of ice in the summer. Otherwise, their distribution would resemble the summer sea ice minimum (Fig. 2), not the winter maximum.
Despite the hue and cry about “declining sea ice,” polar bears are still as well distributed throughout their available winter habitat as they were in 1979, when detailed sea ice records began – see the map below. See further details on polar bear distribution here.
Figure 1. Polar bear distribution map (adapted from the one provided by the PBSG) compared to sea ice concentration at Feb 28 (at or near the seasonal maximum extent) 1979 and 2013. I can’t see a difference – can you see a difference? The only place there is consistently sea ice in winter but not polar bears is the Sea of Okhotsk, but there is no evidence that polar bears have ever lived there despite the presence of seals. Click to enlarge
Benny Peiser over at the Global Warming Policy Foundation has just posted an essay by well-known author Matt Ridley (including “The Rational Optimist”), entitled “We should be listening to Susan Crockford” which is included as a foreword to a pdf of my earlier post, “Ten good reasons not to worry about polar bears.”
This stand-alone pdf is especially suitable for sharing with friends and policy makers.
I encourage you to have a look.
As I mentioned here in an update to my March 7th post, Damian Carrington at the Guardian Environment blog had this telling quote about the CITES deliberations that took place prior to the vote to ban polar bear trade (by uplisting its status from Appendix II to Appendix I):
As the debate raged, national delegates from other countries got confused by the strident but conflicting claims. “Where is the truth? Is it true that the polar bear is declining. Is it true that trade is increasing? We need to know,” said the Egyptian delegate.[my bold]
Indeed. Was there “truth” in the presentations heard by delegates? By that I mean, honest presentations of facts so that delegates could make up their own minds, or facts loaded with spin to sway the decision one way or another? I wasn’t there so I can’t say. But we can get some impression of what might have been said from two
press releases statements issued after the vote failed by two parties that were actively promoting acceptance of the US-led proposal.[Update: Humane Society Press Release is here] Continue reading
Posted in Advocacy, Conservation Status, Population, Sea ice habitat
Tagged advocacy, Chukchi, CITES, Hudson Bay breakup, Humane Society, Polar Bear Specialist Group, sea ice extent, sea ice minimum, US Fish & Wildlife
This article from yesterday about sea ice in the Bering Sea is priceless: while we are still being told that below average ice coverage (common 10-20 years ago) is a sign of global warming that means the end of polar bears sometime in the future, it turns out that too much ice is bad, less ice is friendlier and lots of ice is hopefully something that we’ll never see again.
From the article:
After a 2012 Bering Sea snow crab season that saw unusually severe sea ice inhibit fishermen’s efforts to catch almost 89 million pounds of the shellfish, 2013 is shaping up to be much friendlier.
According to Kathleen Cole, a forecaster with the National Weather Service ice desk, this winter was unlikely to match 2012, even before it began. Despite some recent rumors of encroaching ice into the Bering Sea fishery, the situation is better than last year, she said.
“We’re just not going to have a year like last year. It’s going to be, by no means, that bad,” she said. “Last year was something that we’d never seen before, and hopefully something that we’ll never see again.”
Sea ice is still well above average in the Bering Sea this year – as it has been for 7 of the last 10 years. See the ice extent map from NSIDC from yesterday below and my previous post from December 2012: Now that Bering Sea ice cover is high again, variability is normal (note that polar bears of the Bering Sea are considered part of the “Chukchi Sea” subpopulation, which we know practically nothing about, see previous post here). Continue reading