----- Original Message -----
From: "Roger Smith"

Alastair

No mention any more then of the cessation of the Gulf Stream? That theory
was all the rage not long ago.

Roger

Roger,

As Graham pointed out, the Gulf Stream will not stop, but what they are
worried about is the northern leg of the thermohaline circulation (THC)
or Conveyor stopping. This is a global current, one leg of which is the
North Atlantic Drift (NAD), a tributary of the Gulf Stream, which
oceanographers believe keeps Western Europe warmer in winter than
Labrador at the same latitude. It flows towards the Arctic then sinks
when it cools. The oceanographers fear that the fresh water from
melting Arctic sea ice could float over the salty NAD and prevent it
sinking cooling and sinking thus reinstating ice age conditions.

As an engineer, I see that as impossible, because if the melting ice
caused cooling the ice would reform. There is a strong negative
feedback built into that scenario.

Moreover, Philip Eden pointed out that warmth in Western Europe is due
to winds, not ocean currents, which approach Britain from the South West
and are warmed by the Gulf Stream and Canaries Currents.

However, the New Scientist article went on:

"What's more, the accelerating melt of Arctic ice is injecting a layer
of freshwater into the surface of the North Atlantic and Baffin Bay, off
the coast of Greenland, says Fortier. This may be slowing the
circulation in the Atlantic, which pushes water all through the world's
oceans."

So that idea is not dead as far as climate scientists are concerned.

The idea was first proposed by Wally Broecker to explain the return of
the glacial condition of the Younger Dryas stadial. This happened about
2,000 years after the last glacial period ended 14,000 years ago. I reckon
what happened was that the Arctic sea ice expanded into the GIN
(Greenland, Iceland, and Norwegian) Seas and the cold air which formed
over the ice cause the glacial conditions (and stopped the THC which did
happen.) When the sea ice melted there was a rapid (within three years)
return to interstadial conditions. I expect a similar rapid warming when
the last of the Arctic sea ice disapppears too!

Cheers, Alastair.