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I'm pessimistic because I suspect that the ice shelves are being modelled as more stable and warming-resistant than they really are. A while ago I wrote:
A lot of the climate models seem to have modelled the ice sheets as ice cubes when they behave more like a drop of honey. Ice cubes are very poor heat conductors, insulate their own interior, and only melt on the surface. A drop of honey gets less viscous and flows more easily as it warms up. But I am not an expert on climate modelling.
ARGeezer:replied with
Lately I have been reading articles in Science News and elsewhere about glacial lakes melting holes through very thick glaciers and disappearing through said holes. It appears that this additional water further lubricates the interface between the ice and the rock below, increasing the rate of glacier flow.
I was recalling an article we had discussed in the Salon a couple of years back where some climate scientists suggested that the "ice cube" model used in climate simulations led to melting times of the order of 1,000 years whereas the actual dynamics of the ice shelf might lead it to disintegrate on much shorter timescales.

Then I have seen footage of how meltwater pours into deep crevasses in the Antarctiva ice sheet, going directly to the bedrock where it lubricates the interface between the ice and the rock. I am not convinced large chunks of the Antactica ice cap couldn't simply slide into the sea as a result of this lubrication.

The brainless should not be in banking. — Willem Buitler

by Carrie (migeru at eurotrib dot com) on Mon May 25th, 2009 at 06:32:49 AM EST
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of the geologist, I think that's too pessimist. For now. Don't understand me wrong, if global temperatures creep up another 2 degrees, we are in deep serious - which is why business-as-usual GHG emissions cannot hold.

A few responses up, nanne actually links to one of the articles that illustrate the point, namely:

  1. as far as has been determined, current global temperature is still cooler than the Holocene climatic optimum - particularly in the northern hemisphere.

  2. the last interglacial period (prior to this one) did have 4 - 6 meters higher sea level - but temperatures were an estimated 2 degrees higher. See here and here for examples I've found quickly.

Looking at temperature correlations, we may be seeing calving reaching a new equilibrium and grow constant but on the condition that temperatures stablise.
by Nomad (Bjinse) on Mon May 25th, 2009 at 09:52:25 AM EST
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Nomad:
Don't understand me wrong, if global temperatures creep up another 2 degrees, we are in deep serious - which is why business-as-usual GHG emissions cannot hold.
On that note:



The brainless should not be in banking. — Willem Buitler

by Carrie (migeru at eurotrib dot com) on Tue May 26th, 2009 at 04:12:27 AM EST
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are still something else: bottom is below sea level. Way below. my hunch is that if ocean temps get above a threshold, the WAIS will disintegrate instantaneously.

Patrice Ayme Patriceayme.com Patriceayme.wordpress.com http://tyranosopher.blogspot.com/
by Patrice Ayme on Tue May 26th, 2009 at 07:46:59 PM EST
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