Gulf Stream.

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A major event that occurred 8,200 years ago in which a giant ice dam in North America burst allowed the rapid release of enormous amounts of lake water to drain through the Hudson Strait to the Labrador Sea. It released more than 100,000 cubic kilometres of fresh water and is believed to have disrupted the Thermohaline Circulation (see below), triggering a regional cooling that lasted about 400 years.

The reference can be found on the Natural Resources Canada website: Barber, D.C., A.S. Dyke, C. Hillaire-Marcel, J.E. Jennings, J.T. Andrews, M.W. Kerwin, G. Bilodeau, R. McNeely, J. Southon, M.D. Morehead, and J.M. Gagnon. 1999. Forcing of the Cold Event 8200 years ago by catastrophic Drainage of the Laurentide Lakes. Nature, vol. 400, no. 22, p. 344-348,

Gore says, “The Gulf Stream virtually stopped…Consequently, Europe went back into an ice age for another 900 to 1,000 years.”

Gore uses the term Gulf Stream while he shows pictures of the Thermohaline Circulation (THC). The THC is a convective system driven chiefly by the sinking of denser surface water in the high northern latitudes. The diagram below shows the THC as distinct from the Gulf Stream even though there is an extension to the Gulf Stream that is known as the North Atlantic Drift that is thermohaline circulation driven – this is probably what Gore was referring to. The Gulf Stream itself, on the other hand, is a wind-driven system. It is energized primarily by the Earth’s spin and secondarily by the lunar tides, not by salinity levels in the oceans.  Even if climate models project a weakening of the THC, Europe would still be kept warm by the Gulf Stream proper.

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For a clearer diagram check the source: Broecker, 1991, in Climate change 1995, Impacts, adaptations and mitigation of climate change: scientific-technical analysis, contribution of working group 2 to the second assessment report of the Intergovernmental panel on climate change, UNEP and WMO, Cambridge University Press, 1996.

Also see Wunsch, C. 2004. Gulf Stream safe if wind blows and earth turns. Nature 428: 8.

When discussing the failure of the THC Gore says, “Some scientists are now seriously worried about the possibility of this phenomenon recurring.”

“What are the chances of the thermohaline circulation shutting down?
We don’t yet know the probability of the thermohaline circulation shutting down. It depends on how much and how quickly the atmosphere warms. In general, it is considered possible but not very likely. If it were to occur, it would probably not happen within the next 100 years, and circulation would eventually recover, after decades or centuries.”

See Pew Center on Global Climate Change. “The Day After Tomorrow: Could it Really Happen?”

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Gore does at least acknowledges that there is no ice dam to burst anymore and then goes on to ask rhetorically if there is another source of ice while the camera moves up to Greenland. This hobgoblin is speculative and exaggerated to say the least.