Tuesday, January 15, 2013

Another ice entrapment

           The ice entrapment of 11 killer whales last week generated international media attention and raised concerns about the increasing frequency of such events and how best to address them.  It appears that a shift in wind and ice enabled the whales to escape this time, changing what could have been a horrifying story into a somewhat heartwarming one. But that is likely the exception to the rule.
Photo by ABC News
            As I wrote last winter when dozens of beluga whales became entrapped by closing ice in the Bering Sea near Russia, ice entrapments of large numbers of whales has been infrequent through the years, though the Arctic is so thinly populated that no one is around to observe or document entrapments in the vast majority of the region.  When 600 narwhals were entrapped off Baffin Island in Nunavut in 2008, local Inuit hunters said the last entrapment they recalled occurred way back in 1943.  But there are fears that climate change is increasing its frequency.
            Narwhal biologist Kristin Laidre at the University of Washington told me that four ice entrapments that resulted in the deaths of more than 700 narwhals occurred in 2008 and 2009 – the first one ever documented in East Greenland, as well as two in northwest Greenland and the very large one near Pond inlet.
Laidre is beginning to examine the distribution and timing of known ice entrapments and look at the trends in the breakup of sea ice on the narwhal’s summering grounds. She has found what she calls “strongly significant trends” that suggest that the ice is forming later and later.  “Over a 30 year period there is a three to four week difference in when the ice forms,” she said.  “If ice formation is a clue to the narwhals that it’s time to get out of their summering grounds, then the trigger is changing, the pattern is changing.” 
Is that change in the formation of ice making narwhals more vulnerable to ice entrapments?  Laidre hypothesizes that it may be the case, though there is precious little data from which to draw conclusions just yet.  But the hints she has found so far are another indication of the dangerous implications of global warming.

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