Monday, October 29, 2007

On the shelf

Al Gore is fat, right, and a screeching Cassandra, right, so we needn't take what he says, seriously, right? That stuff about 20-feet rises in sea level, blah blah, all nonsense, right?

Right. The sea is not likely to rise 20 feet any time soon. (But not likely is not not at all.)

The thing is, this is why I take him seriously. We have no idea how close to falling into the sea Greenland's ice is. But we do know that it would be catastrophic if it does. And it's not just a case of fuck it, I'll just go live up a mountain.

The Larsen B ice shelf fell into the sea over 35 days. One day it was there, proud and frigid, just over a month later, it was pretty much gone. More than three thousand square kilometres of ice, whack, straight into the ocean. (Our American friends may like to know that that's a bigger area than Rhode Island; Europeans, it's more than Luxembourg and slightly smaller than Cornwall.) That structure had existed for at least 400 years, and probably for 12K years, since the last glaciation. Well, the sea didn't rise 20 feet, because Larsen B is only tiny as ice sheets go. Greenland's sheet is more than a million square kilometres. We know it's melting, but we don't know how fast. Scientists cannot accurately model ice-shelf breakage, because it is so complicated and has so many variables, so they are left saying, let's hope it doesn't.

The chance is not nil though and the outcome would be horrendous. A Larsen-type event in Greenland could dump an enormous amount of ice into the North Atlantic. Well, so what? The so what is that a large influx of ice could disrupt -- even stop -- the ocean circulation, as well as raise sea levels. The headline outcome of that would be that the UK and Western Europe, which have a mild climate because of the Gulfstream, which brings warm water -- and by extension warm air -- from the Gulf of Mexico, would instead have climates that matched those of other places at the same latitude. Which is Labrador. Or Moscow but with more storms.

Still, we would not be in a position to worry about that for long, because that would not be the worst of it. If the sea stops circulating, the seabed will be warmed by the Earth's internal heat and the deep sea will become anoxic. This will do two things. Allow the release of sequestered methane and create the environment in which bacteria that like eating methane and shitting out sulphides thrive. The deep sea holds sulphides, which cannot escape because of reasons I can't explain but do understand (I know that sounds weird but when I read about a "chemocline", I understand what it means but don't know why it works, so can't really describe it), and can hold them up to a point. Once that point is passed, wham. Hydrogen sulphide -- the "rotten egg" gas -- would belch up from the deep in enormous quantities.

It's believed this may have happened before. Unless you are planning on patenting a method of breathing hydrogen sulphide, it will not be pleasant for you.

Yeah, it's not all that likely. And Al Gore is totally fat. But it's much more likely than winning the lotto, and I buy a ticket for that every Saturday.


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