Tuesday, January 15, 2008

Around the Cryosphere

Today I was looking for information related to changes in the Arctic sea ice and found the National Snow and Ice Data Center, (NSIDC) - yes there is such a thing- run out of the University of Colorado. There is even a word for the snow and ice and glaciers that make up the frozen water part of this planet-the cryosphere. Seems like a minor environmental niche until you think about the important role that ice plays not only in the energy budget of the Earth by altering the reflectivity of the planet, but also ecologically.

The NSIDC has a great series of graphics related to sea ice and glaciers. For instance, here are two shots of Muir Glacier from the same vantage point, one taken in 1941 and the second taken in 2004. The difference is quite sobering though I am sure those people who don't think we need to be concerned about climate change can put a positive spin on all the vegetation present in 2004. Of course not all glaciers are melting. Climate change is much more complex than we sometime think.



There is lots of information about the polar regions including some features, quite new to me. For instance, in the Antarctic, there are structures called megadunes. These features are so large that a person on the surface doesn't really notice them, and it is only with satellite imagery that they can be properly visualized. How they form is not clear, but they seem to be made by the winds carving into the ice rather than by wind deposited snow.




I don't think anyone is seriously thinking that the cryosphere will disappear completely. Also, the movie Waterworld may be a great story but it is just that-were all the ice to melt the Earth would not end up completely covered in water. Even during the warmest part of the Creataceous period roughly 90 million years ago, there is evidence of extensive glaciation. But the best available models predict rapid loss of the arctic sea ice as discussed in this post from RealClimate.

In fact, during the late 1960's and early 1970's the concern among some scientists was that we might soon enter another ice age. Global warming skeptics are fond of pointing this out. There were several reasons for thinking this might be plausible. First it was thought that statistically we have been in a relatively long interglacial period so the thought was maybe we are just due for a period of cooling. This was re-enforced by a short term cooling trend that began in the 1940's. Next, some scientists thought that the effects of dust and soot in the air, might counteract the warming due to the excess carbon dioxide produced by human activity.

Global warming skeptics often conveniently ignore the fact the issue wasn't the reality of human induced global warming, but that other factors might counteract it. New Scientist has an article discussing the global cooling idea that meshes well with what I remember of these debates, ongoing when I was an undergraduate.

Curiously the cooling idea has been been advanced again by some scientists who hypothesize that global warming might have the paradoxical effect of cooling the climate in Europe. The basic idea is that fresh water added to the North Atlantic would stop the flow of heat via ocean currents to Europe. However, scientists are still debating this possibility and improved understanding of ocean currents heat transfer in the ocean suggests that this cooling will not happen.

So the ice is melting. But we must be careful not to ascribe all that melting to human activity. For example, a recent report,summarized in Science Daily, suggests that at least some of the melting of the Greenland ice cap might be due to heat from inside the Earth. There is a Lawrence Kansas connection since one of the scientists involved, Timothy Leftwich from Oregon State University, is a post doc associated with a consortium called CRESIS, the Center for Remote Sensing of Ice Sheets. KU is the lead institution for the consortium.
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