Just think like an icecap.

Glacier atop Kilimanjaro. DL 2010

Iceskates are like glaciers.  Really.

So I’m undergoing my first formal paleoceanography and paleoclimatology course, and I just learned about this unlikely analogy.  For the thermodynamically uninitiated among us, the ice at the bottom of a glacier can actually melt even when ambient temperature is well below the freezing point.  As a glacier accumulates snow (and thus as it compacts and more or less forms ice), the glacier gets quite heavy, and the pressure that the glacier exerts actually causes the ice near the bottom to melt.  No heat transfer required.  Sometimes ice masses can get heavy enough to depress a continent, as in the case of Antarctica, a phenomenon known as isotasy–for example, if the icecap disappeared, sea level would rise and the landmass would begin to rise as well, albeit on a longer timescale.  But as glaciers melt ice within their depths, they’re providing a sort of slick to slide along with their enormous mass (one reason that you don’t see any glaciers trudging uphill).  Iceskates work in the same fashion–your weight is focused over a very small surface area (i.e. the blade) and presto chango, the ice right under the blade melts and provides lubricant to slide along with.  If you’re really interested in what’s going on at a molecular level within the ice crystals and have a penchant for physical sciences, you can go here.

So the attentive reader, by now should have thought about Antarctica, our temporarily (at least in geologic time) fixed polar landmass.  Is there ice melting under the ice cap due to pressure?  Yep.  And there are subglacial lakes.  Isn’t that crazy?  Lakes (i.e. water in the liquid phase) under an ice cap?  The largest of which is Lake Vostok, which has been covered by ice for perhaps 25 million years and is about the size of Lake Ontario.  There is also a possibility that psychrophiles (cold-loving microbes) may exist within this extraordinarily isolated lake, which is currently under 4 kilometers of ice.  Microbial life has already been found in ice cores above Lake Vostok at depths of about 3600 meters.  For more in-depth information, Dr Robin Bell and her colleagues at Lamont-Doherty Earth Observatory at Columbia have concocted a nifty flash animation of glacial processes and research going on at Vostok.

So speaking of glaciers, I really can’t help but to mention Kilimanjaro.  A recent study shows that of the ice present in 1912, 85% is gone.  Of the ice present in 2000, 26% is now gone.  These losses in glacial cover at high elevations suggests that warmer air temperatures are a dominant mechanism at work here, along with localized issues of land use, precipitation, and cloud cover.  The ice fields (of which there are 3 left on Kili) obviously will not be around much longer under our current climatological regime.

Price BP, 2000. A habitat for psychrophiles in deep Antarctic ice. PNAS 97:3.  1247-1251.
Thompson LP, 2009.  Glacier loss on Kilimanjaro continues unabated. PNAS 106:47. 19770-19775.

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