Alastair McDonald wrote:
----- 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.

Thanks Alastair. Most interesting.

As always, there are a number of theories, many of which have conflicting
outcomes. Only time will tell which of the many factors will predominate
and the nature of the climate change in different parts of the world.

Regards, Roger