Annals of global warming: No, polar bears are not “fine” — suffer from loss of sea ice

Press release from The Journal of Animal Ecology (links added here):

For polar bears, it’s survival of the fattest

One of the most southerly populations of polar bears in the world – and the best studied – is struggling to cope with climate-induced changes to sea ice, new research reveals. Based on over 10 years’ data the study, published in the British Ecological Society‘s Journal of Animal Ecology, sheds new light on how sea ice conditions drive polar bears’ annual migration on and off the ice.

Led by Dr. Seth Cherry of the University of Alberta, the team studied polar bears in western Hudson Bay, where sea ice melts completely each summer and typically re-freezes from late November to early December. “This poses an interesting challenge for a species that has evolved as a highly efficient predator of ice-associated seals,” he explains. “Because although polar bears are excellent swimmers compared with other bear species, they use the sea ice to travel, hunt, mate and rest.”

Polar bear and two cubs wait for ice to reform

Caption from EurekAlert: An adult female polar bear wearing a GPS-satellite linked collar with her two 10-month-old cubs waits for the sea ice to re-form onshore in western Hudson Bay, Manitoba, Canada. Photo Copyright Andrew Derocher, Univeristy of Alberta.

Polar bears have adapted to the annual loss of sea ice by migrating onto land each summer. While there, they cannot hunt seals and must rely on fat reserves to see them through until the ice returns.

Dr. Cherry and colleagues wanted to discover how earlier thawing and later freezing of sea ice affects the bears’ migration. “At first glance, sea ice may look like a barren, uniform environment, but in reality, it’s remarkably complex and polar bears manage to cope, and even thrive, in a habitat that moves beneath their feet and even disappears for part of the year. This is an extraordinary biological feat and biologist still don’t fully understand it,” he says.

From 1991-97 and 2004-09, they monitored movements of 109 female polar bears fitted with satellite tracking collars. They tagged only females because males’ necks are wider than their heads, so they cannot wear a collar. During the same period, the team also monitored the position and concentration of sea ice using satellite images.

“Defining precisely what aspects of sea ice break-up and freeze-up affect polar bear migration, and when these conditions occur, is a vital part of monitoring how potential climate-induced changes to sea ice freeze-thaw cycles may affect the bears,” he says.

The results reveal the timing of polar bears’ migration can be predicted by how fast the sea ice melts and freezes, and by when specific sea ice concentrations occur within a given area of Hudson Bay.

According to Dr. Cherry: “The data suggest that in recent years, polar bears are arriving on shore earlier in the summer and leaving later in the autumn. These are precisely the kind of changes one would expect to see as a result of a warming climate and may help explain some other studies that are showing declines in body condition and cub production.”

Recent estimates put the western Hudson Bay polar bear population at around 900 individuals. The population has declined since the 1990s, as has the bears’ body condition and the number of cubs surviving to adulthood.

Young polar bear challenged by lack of sea ice, Andrew Derocher photo

Caption from EurekAlert: This is a subadult polar bear on a lake on the shores of Hudson Bay in Manitoba, Canada in November waiting for the sea ice to re-form. Copyright Andrew Derocher, Univeristy of Alberta.

Because polar bears’ main food source is seals, and these are hunted almost exclusively on sea ice, the longer bears spend on land, the longer they must go without energy-rich seals. “Climate-induced changes that cause sea ice to melt earlier, form later, or both, likely affect the overall health of polar bears in the area. Ultimately, for polar bears, it’s survival of the fattest,” says Dr. Cherry.

He hopes the results will enable other scientists and wildlife managers to predict how potential climate-induced changes to sea ice freeze-thaw cycles will affect the ecology, particularly the migration patterns, of this iconic species.


Seth Cherry et al (2013). ‘Migration phenology and seasonal fidelity of an Arctic marine predator in relation to sea ice dynamics’, doi: 10.1111/1365-2656.12050, is published in the Journal of Animal Ecology on Wednesday 20 March 2013.


8 Responses to Annals of global warming: No, polar bears are not “fine” — suffer from loss of sea ice

  1. Ed Darrell says:

    Journal of Animal Ecology and Wiley have made the Cherry/Derocher article available free:


  2. JamesK says:

    Yes, yes, people are getting dumber. It’s called Republicanitis.

    It has two other names “Conservatitis” and “Teabaggeritis.”


  3. Ed Darrell says:

    Are people getting dumber?

    Dumb first, then dumber — pushing on to pure stupid.

    Misquoting movies: “Facts? We don’t got no facts. We don’t need no STINKIN’ FACTS!”

    Making Bertrand Russell a prophet.

    Making false ridicule of DaVinci, who surely would have said, “Eppure, lei si scalda.”


  4. jsojourner says:

    Ah, nice. The old, “It was cold this winter. Ergo, climate change is a myth” meme.

    Are people getting dumber?


  5. […] Annals of global warming: No, polar bears are not “fine” — suffer from loss of sea…. […]


  6. Ed Darrell says:

    Mark at Pseudo-Polymath and Stones Cry Out, drily (and he hopes, drolly) notes in denial:

    Interesting post on the first day of Spring when it’s 13 degrees out (and global temperatures have been flat for almost 20 years).

    Argument by analogy is dangerous, but those who eschew facts and reality for faith, especially in issues of science, sometimes appear unable to understand any other way. So here goes.

    Mark, global warming is a lot like altitude sickness. You get altitude sickness when you get too high in elevation; best immediate cure is to come down to lower elevation. The Earth gets global warming when carbon dioxide gets too high. Best immediate cure is to bring down CO2 levels.

    If a human has altitude sickness, they may feel no worse if they lie down for a while. But they are still sick, and still at risk, so long as they are at altitude. If a guy gets ill at 11,000 feet, noting that while staying at 11,000 feet they haven’t died yet, is not the same thing as saying altitude sickness has abated, and it’s foolish at that point to pretend the guy is healthy, nor even healthier.

    Temperatures haven’t plateaued for 20 years — there’s that old Denial Virus making people crazy again — but if they had, we’d be foolish to think things are okay, especially since CO2 levels continue to rocket (see counter on the bottom right side of this blog). See these ten charts that show the error of that Denialism, Inc., chart you link to, to begin. If you’re serious about understand the chart, what it says, and how it mangles statistical work in climate change, here’s a pretty good lay explanation.

    You’ve doomed the altitude-sick guy to serious heart, lung and brain damage, and perhaps death, Mark, just as “Gormogon” wants to doom the planet. Don’t pretend Jesus said leave the lamp wicks untrimmed and the oil vessels empty so long as the Sun shines; don’t pretend Daniel said, “We’ve got seven bad years coming, so let’s binge eat, binge drink and be merry now, for tomorrow we die.”

    Denialism blinds otherwise intelligent, and otherwise compassionate, people to odd, often destructive behaviors. Heck, it dooms them to self-destructive behaviors.

    (Bad enough these guys don’t know their own scriptures; hate it when they misinterpret science as if they had the facts.)

    And, Mark, you missed the entire point: It doesn’t matter what your denialist charts show. The bears don’t have internet, nor newspapers, nor college libraries, and they don’t even get daily weather forecasts. The decline in polar bears is real. You claim the explanation of the experts is wrong, and therefore there is no problem?

    Even you ought to be able to see the denialism symptoms there, and how denialism isn’t helping the bears.


  7. […] post on the first day of Spring when it’s  13 degrees out (and global temperatures have been flat for almost 20 […]


  8. […] post on the first day of Spring when it’s  13 degrees out (and global temperatures have been flat for almost 20 […]


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