Chilling effects. Via EnergyBulletin.net (an important resource on, er, resources, and thanks to James Wolcott for pointing me to it), an extremely disturbing article from the UK Sunday Times:

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. ...

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’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.

As the article goes on to note, the effects of a weakening or even shutdown of thermohaline circulation in the North Atlantic are extremely difficult to predict: it could mark the beginning of another Little Ice Age in Northern Europe (and possibly the Atlantic United States), it could merely mean that Europe cools, relatively, within a more general warming.

The point here is that the climate-change schedule seems to be accelerating. From the Peak Oil perspective, that's very bad news: significant, abrupt shifts in local temperatures and rainfall are a major additional stressor (on the energy economy, on food production, on population) that we really can't afford to face while we're trying to manage the end of the fossil-fuel era. (Climate shifts all on their own have historically been major social challenges.) If the disruptive effects of global warming are going to start manifesting within the next two decades, I have to think that significantly reduces our odds (low enough as it is) of finding a sane, more-or-less peaceful transition out of the oil regime.

posted by michael  9:37:49 AM  
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