Norsemaiden
barbarian
Its very important to realize the importance of ocean salinity, especially in terms of the North Atlantic Deep Water Current. This, essentially, allows for a temperate climate in Europe, Russia, and North America (and similar latitudes).
Polar melting disrupts ocean salinity, which at some point will cross a threshold and essentially invert this current, triggering glacial expansion, mostly likely across the northern latitudes mentioned (Ice Age).
The frightening thing about this is that its not gradual- its a threshold. If the salinity reaches a point, it more or less "snaps". Severe climate change could be very rapid after this point (measured in terms of months, not decades).
Yes - the Gulf stream is slowing substantially and that will have dramatic results just as you say.
http://www.timesonline.co.uk/tol/news/uk/article520013.eceCLIMATE change researchers have detected the first signs of a slowdown in the Gulf Stream — the mighty ocean current that keeps Britain and Europe from freezing.
They have found that one of the “engines” driving the Gulf Stream — the sinking of supercooled water in the Greenland Sea — has weakened to less than a quarter of its former strength.
The weakening, apparently caused by global warming, could herald big changes in the current over the next few years or decades. Paradoxically, it could lead to Britain and northwestern and Europe undergoing a sharp drop in temperatures.
"Models show that if it shuts down completely, 20 years later, the temperature is 4C to 6C degrees cooler over the UK and north-western Europe," Dr Bryden said.
http://www.guardian.co.uk/science/story/0,3605,1654803,00.html
The global warming elsewhere would continue.
Even if a slowdown in the current put the brakes on warming over Britain and parts of Europe, the impact [of continued warming] would be felt more extremely elsewhere, he said.
This is the most up to date reference I could find - from 2 Feb 2007
http://members.greenpeace.org/blog/jamesdneovi