[Peakoil-announce] Gulf stream diminishing

[Alex P]

"The Day After Tomorrow" presents the scenario of Britain suddenly 
freezing over due to climate change. But apparently the gulf stream really 
is now diminishing.

This should be a spur to strong action from the British Government.

In other news, the ALP in NSW is likely to start subsisiding ethanol 
production as a petrol substitute, as in Qld. But this is only good policy 
if there is a net energy gain - no point burning petrol to drive tractors 
to make ethanol containing less energy than the petrol you started with.

Alex
O4O4873828

ACT Peak Oil discussion list
http://www.act-peakoil.org
________________________________________

Britain faces big chill as ocean current slows

Jonathan Leake, Science Editor
The Times Online (UK) 
May 08, 2005
http://www.timesonline.co.uk/article/0,,2087-1602579,00.html

CLIMATE 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.

Such a change has long been predicted by scientists but the new research 
is among the first to show clear experimental evidence of the phenomenon.

Peter Wadhams, professor of ocean physics at Cambridge University, hitched 
rides under the Arctic ice cap in Royal Navy submarines and used ships to 
take measurements across the Greenland Sea.

"Until recently we would find giant 'chimneys' in the sea where columns of 
cold, dense water were sinking from the surface to the seabed 3,000 metres 
below, but now they have almost disappeared," he said.

"As the water sank it was replaced by warm water flowing in from the 
south, which kept the circulation going. If that mechanism is slowing, it 
will mean less heat reaching Europe."

Such a change could have a severe impact on Britain, which lies on the 
same latitude as Siberia and ought to be much colder. The Gulf Stream 
transports 27,000 times more heat to British shores than all the nation's 
power supplies could provide, warming Britain by 5-8C.

Wadhams and his colleagues believe, however, that just such changes could 
be well under way. They predict that the slowing of the Gulf Stream is 
likely to be accompanied by other effects, such as the complete summer 
melting of the Arctic ice cap by as early as 2020 and almost certainly by 
2080. This would spell disaster for Arctic wildlife such as the polar 
bear, which could face extinction.

Wadhams's submarine journeys took him under the North Polar ice cap, using 
sonar to survey the ice from underneath. He has measured how the ice has 
become 46% thinner over the past 20 years. The results from these surveys 
prompted him to focus on a feature called the Odden ice shelf, which 
should grow out into the Greenland Sea every winter and recede in summer.

The growth of this shelf should trigger the annual formation of the 
sinking water columns. As sea water freezes to form the shelf, the ice 
crystals expel their salt into the surrounding water, making it heavier 
than the water below.

However, the Odden ice shelf has stopped forming. It last appeared in full 
in 1997. "In the past we could see nine to 12 giant columns forming under 
the shelf each year. In our latest cruise, we found only two and they were 
so weak that the sinking water could not reach the seabed," said Wadhams, 
who disclosed the findings at a meeting of the European Geosciences Union 
in Vienna.

The exact effect of such changes is hard to predict because currents and 
weather systems take years to respond and because there are two other 
areas around the north Atlantic where water sinks, helping to maintain 
circulation. Less is known about how climate change is affecting these.

However, Wadhams suggests the effect could be dramatic. "One of the 
frightening things in the film The Day After Tomorrow showed how the 
circulation in the Atlantic Ocean is upset because the sinking of cold 
water in the north Atlantic suddenly stops," he said.

"The sinking is stopping, albeit much more slowly than in the film - over 
years rather than a few days. If it continues, the effect will be to cool 
the climate of northern Europe."

One possibility is that Europe will freeze; another is that the slowing of 
the Gulf Stream may keep Europe cool as global warming heats the rest of 
the world - but with more extremes of weather.