Sunday, February 16, 2014

Baffin Island melting unprecedented


This photo shows one of the many glaciers on Baffin Island, in the far northern reaches of Canada. New research from this island tells a stark story of how unstable these glaciers are becoming.

Baffin Island is in the middle of the area strongly affected by Milankovitch cycles. As the Earth wobbles in its orbit, northern Canada is seeing particularly large swings in the amount of sunlight it receives, making it a key contributor to the expanding and melting of ice sheets.

Right now, we’re at a point where solar input to Canada is declining. About 11,700 years ago, the solar energy input to this area was about 9% greater than it is today; at about the same time, the large ice sheets covering Canada were collapsing.

Not every glacier in Canada collapsed, particularly here in Baffin Island, just the large ice sheet. But, since these glaciers aren’t linked to the large ice sheet, one would expect that Baffin Island is a place on Earth that should be cooling right now. It is getting less sunlight than it did 10,000 years ago, so if any place on Earth should be slowly cooling, it should be right here.

A new study led by Dr. Gifford Miller at CU Boulder found something remarkable. These glaciers are melting slowly at their edges, releasing some plants and rocks that have been trapped in the ice. These scientists sampled some of those plants, expecting that their radiocarbon ages would be a sign for how long the plants had been trapped in the ice. Using that information, they could estimate how much the glaciers of Baffin Island grew as the solar input decreased.

When they got a radiocarbon date on those formerly-frozen plants, they found that to their surprise the age was infinite. Radiocarbon dating doesn’t provide solid answers past about 40,000 years even in the best labs – beyond that the calculated age goes to infinity, so these plants must have been much older than 40,000 years – a time when all of Canada was covered by ice sheets.

Their conclusion is that these plants were trapped in ice during a previous time in-between the formation of ice sheets. The most recent inter-glacial time was about 125,000 years ago – a likely time for these plants to be trapped.

The presence of these plants means a couple things. First, ice that hasn’t melted in at least 125,000 years is melting today. Second, that ice is melting even though the amount of sun coming in to Baffin Island today is decreasing – the changing global climate is overwhelming the decreasing solar input.

Finally…125,000 years ago, the ice sheets on Greenland and Antarctica melted a lot more than they did in this inter-glacial period. If these plants are from that time…they come from a time when sea level was between 5 and 9 meters higher than it is today. To say that a different way, the last time the these plants were outside of a glacier, sea level was about twice the height of the hurricane Sandy storm surge in New York.


Image credit:
http://commons.wikimedia.org/wiki/File:Glacier,_Glacial_Lake,_and_Terminal_Moraine,_Baffin_Island_-a.jpg
Original paper:
http://dx.doi.org/10.1002/2013GL057188
Press report:
http://instaar.colorado.edu/news-events/instaar-news/instaar-study-shows-unprecedented-warmth-in-arctic/

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