Friday, October 5, 2007

Ice age favours North

Another reason to start 'house cleaning' at the North Atlantic thermohaline conveyor belt. Ice age if it comes, may affect less the the Southern hemisphere.

We knew from earlier and Change-Climate-Back has reported on this at some length that the warming will actually increase ice in the Antarctic because snow precipitation there is still more than ice melting.

We have also reported that due to fresh-water leaks from melting ice in the North Atlantic the thermohaline circulation here (also known as the Gulf Stream) has already weakened significantly. Some estimate that decrease at 30%. The process may foreshadow a potential shut down of the circulation, which from earlier data appears to conclude in 3 short years substantially decreasing the mean temperature at the North - that is much of the northern part of the Northern hemisphere.

But it has received less public attention that the Atlantic and the Pacific ocean conveyor belts are linked though the connection appears less direct. There may also exist a substantial delay between a mass off water exiting the one stream and entering the other.

But the sum effect of that link according to a report by Timothy Burrows published in the journal Science is that when it works the south exports heat to the north. But when the link is broken, there is no more export and the cooling of the Northern hemisphere is offset by a relative heating of the South.

This appears to have happened many times over, most notably at the end of the last Ice Age called the Younger Dryas geological event around 13,000 years ago. This meant rapid cooling for the North right after rapid Global Warming at the end of the Ice Age called the Pleistocene geological epoch. It was due to the same process that is happening now - the rapid mass melting of the Northern ice sheets that accompanied rapid global warming shut down the Gulf.

Back then the Southern hemisphere actually got warmer with the mean temperature here being 2 degrees higher than it is now.

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