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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.

On Peak Coal, when people throw around estimates that there are 200 years' worth of reserves at current extraction rates, they forget that at, say, 3% yearly growth of extraction rates there's barely 50 years' worth, and if coal starts picking up the oil slack the growth rate of use will be larger than 3%. We should worry about peak fossil carbon.

Or then again, maybe not. Burning all the fossil carbon is one of the stupides things we can do, climate-wise.

When the capital development of a country becomes a by-product of the activities of a casino, the job is likely to be ill-done. — John M. Keynes

by Carrie (migeru at eurotrib dot com) on Mon Jun 2nd, 2008 at 07:05:18 AM EST
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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.

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. Such processes have been observed both in Greenland and West Antarctica.  I believe that the melting of the two ice sheets would product an increase of about 70 meters in sea level.

I recall an article arguing that the break-up of the North American Ice Sheet at the end of the last ice age had occured quite rapidly and that the influx of fresh water had temporarily disrupted the Gulf Stream and that this accounted for an unexplained episode of re-glaciation in Western Europe.  Non-linear processes can proceed quite rapidly.  This is what makes me worry that it may be later than we think.

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Wed Jun 4th, 2008 at 10:14:11 PM EST
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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.
Right! In hindsight, this should have been predictable.

Since ice floats in water, a water lake on top of a glacier is metastable and really wants to be under the glacier. The question is, how does it get there without freezing over?

As you know, around the ice/water phase transition a pressure increase can induce melting (due to the lower specific volume of water). Thus, if the lake is deep enough, hydrostatic pressure at the boundary may be large enough to induce melting. The open boundary of the lake will probably undergo some freezing, but once frozen over the ice layer acts as a thermal insulator and this process slows down. The pressure melting of ice at the bottom is a runaway process.


When the capital development of a country becomes a by-product of the activities of a casino, the job is likely to be ill-done. — John M. Keynes

by Carrie (migeru at eurotrib dot com) on Thu Jun 5th, 2008 at 02:41:35 AM EST
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