The latest guesstimate to fall is the Greenland ice sheet. It's melting faster than we anticipated. What is it this time? It's these things:
See those dark spots on the surface of the ice sheet? They're called "supraglacial lakes." They're surface meltwater and, as the Arctic continues to warm, they're expected to grow both in numbers and in size. They would be a lot bigger already except that many of them manage to drain down through the ice sheet where the rivers of meltwater lubricate the ice above and speed its flow to the sea.
As those lakes grow and spread they also absorb more solar energy than the ice, accelerating the melt. Here are some images to show how the Greenland ice sheet is decomposing:
No one has an accurate estimate of what this will mean in terms of sea level rise. What is known is that the estimate of 8 inches of rise by 2100 caused by the Greenland ice sheet is way off the mark.
The critical word is acceleration. The melt will get faster and faster. We are not faced with a fixed rate of melt that planners can rely on. Picking a particular date for a particular target is a mug's game. We need to think in terms of compounding.
ReplyDeleteI don't know what numbers to use but, as an example, if the ice melt were to double every year we would have a terrible mess by 2050.
There are indeed many contributing factors in play, Toby. There's the black soot problem, a steadily warming atmosphere and ocean, these lakes and the runoff that gets beneath the ice sheet and, to varying extents, each compounds the others.
ReplyDeleteHi
ReplyDeleteNot sure if you've linked to this site:
http://arctic-news.blogspot.ca/
If this site is anywhere close to accurate in its predictions....Yikes!
Best of the Season
Thanks for the Arctic News link, Anon. I haven't been there for a few months and it is a very useful site. As for their dire predictions of a near-term extinction I can only hope they're wrong.
ReplyDeleteI live an hour from Alaska and the last few years have been the mildest winters since I moved up here. Yesterday was -2C and we have only gone below -10C for a few nights since September. Normally this time of year is -20C in the day and -30C at night. Anybody with wood heat backup which is most of us have barely used anything else. This is doubly good for the environment as any catalytic stove either wood or pellets as less pollution than natural gas.
ReplyDeleteI've been following the changing conditions up your way, Bill. It bears out my contention that the more pristine the environment the more noticeable are the impacts of climate change. People in large urban centers are far more likely to question climate change because their congested regions create their own climate.
ReplyDeleteWhen I lived in West Vancouver out toward Horseshoe Bay, our cherry trees would blossom almost 2-weeks later than those in Vancouver proper. Here on Vancouver Island it's later yet.
As we've learned from the ravages of the pine beetle, mild winters can bring a mixed outcome. Overall I don't think they're beneficial.
Anon thank you for the link I can't get over how 'the ice giant' seems to be hanging onto Greenland and laying on it's back on the Canadian North. Um...
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