At the seasonal minimum 2015, the Arctic Basin was still almost full of sea ice, down only 0.3 mkm2 below the maximum it could ever be.
Remember that spending the summer in the Arctic Basin for most polar bears is just like sitting on the western shore of Hudson Bay – they are all waiting for the refreeze. In either location, they might find something to eat, they might not.
Below are NSIDC MASIE sea ice maps for 10 April 2015 (as big as it gets, basin filled) vs. 17 September 2015: Continue reading
Two out of seven polar bears with collars in the Southern Beaufort Sea either spent the month of August on ice that satellites couldn’t see – or they spent the entire month swimming around the Beaufort. Which seems most likely?
See previous discussions here and here regarding the problem satellites have in accurately detecting melting ice. The presence of these two bears is evidence that there is more polar bear habitat than satellites record as officially present. This was also an issue for Hudson Bay bears earlier this year.
Five out of the seven visible females were on the ice in August – but are the other six bears that were visible last month spending the summer in the Arctic Basin like the one I reported last week? Or have their collars actually failed or dropped off? USGS isn’t saying.
See the August track map below, from the USGS Tracking Polar Bears website1 and a sea ice map.
Researchers in the Arctic Basin yesterday spotted a hugely fat pregnant polar bear female on broken ice over water about 2,500 meters deep. Some people seem to find this surprising but it’s what I discussed last week.
Photo above by Tim Kenna from aboard the Coast Guard cutter Healy. Researchers are in the area as part of the “TRACES of Change in the Arctic” program. Another perspective on the bear and the location it was spotted on 24 August 2015 below, as well as some background on Arctic Basin bears.
At this time of year, sea ice extent numbers are meaningless for polar bears. The extreme low September minimum of 2012 – when masses of polar bears didn’t die – showed rational people that this is true. Even the low 2007 summer extent, which hit earlier in the season than 2012, had little to no negative impact.
In late summer, bears outside the Canadian Archipelago either retreat to shore or stay on the sea ice as it retreats north into the Arctic Basin (see image below, click to enlarge). Most bears in the Archipelago have ice year round, so life doesn’t change much. This means that it does not matter to polar bears how much area the Arctic Basin ice covers in September – for their needs, 1.0 mkm2 would be plenty.
Still, Southern Hudson Bay polar bears had extended hunting opportunities in July this year (whether or not they hunted successfully) and for this date, Hudson Bay had more ice remaining than any year on record. Yes, more than even 1992 but only by a few percent. See charts and maps below.
Posted in Life History, Sea ice habitat
Tagged Arctic basin, fasting, habitat, Hudson Bay, MASIE, minimum, passive microwave, polar bear, sea ice, September, starving, summer, thin ice
While the polar bear is an Ice Age species, genetic and fossil evidence suggests it barely survived the profound sea ice changes associated with the Last Glacial Maximum, one of the most severe glacial periods of the Pleistocene.
A map of sea ice extent at the climax of the Last Glacial Maximum (both perennial and seasonal ice), prepared with the help of a colleague, makes it possible to discuss what genetic and fossil evidence can tell us about the probable effects of glacial conditions on polar bears and ringed seals.
Posted in Evolution, Sea ice habitat
Tagged Arctic basin, genetic bottleneck, ice age, last glacial maximum, LGM, perennial ice, Pleistocene, polar bear, population bottleneck, population decline, ringed seal, sea ice, sea ice habitat, sea level, seasonal ice
In an attempt to get themselves out of a mess of their own making, the IUCN Polar Bear Specialist Group (PBSG) has just dug their hole even deeper.
Although the minutes of their 2014 June meeting (pdf here) contained this statement…
“K. Laidre summarized the need for the PBSG to do a better job of communicating accurate and balanced science about polar bears.” Pg. 28
…you might conclude, after reading the rest of this post, that polar bear specialists don’t really understand what these terms mean.
Due to the flack they have been catching over their global polar bear population estimates, the PBSG determined that another clarification was in order. [As opposed to the first clarification, a footnote the group planned to insert in an upcoming report, which PBSG chairman Dag Vongraven sent to me in May)]
The new clarification, apparently co-authored by Steve Amstrup and Andy Derocher (PBSG 17 minutes, pg. 33 – copied below), makes an astonishingly bold claim that I can easily show is untrue.
Posted in Population
Tagged Amstrup, Arctic basin, communication, Derocher, East Greenland, footnote clarification, global population estimate, Kristin Laidre, PBSG, polar bear population estimate, polar bears, status table