ScienceDaily (Nov. 30, 2009) — In the film The Day After Tomorrow, the world enters the icy grip of a new glacial period within the space of just a few weeks. Now new research shows that this scenario may not be so far from the truth after all.
William Patterson, from the University of Saskatchewan in Canada, and his colleagues have shown that switching off the North Atlantic circulation can force the Northern hemisphere into a mini 'ice age' in a matter of months. Previous work has indicated that this process would take tens of years.
Around 12,800 years ago the northern hemisphere was hit by a mini ice-age, known by scientists as the Younger Dryas, and nicknamed the 'Big Freeze', which lasted around 1300 years. Geological evidence shows that the Big Freeze was brought about by a sudden influx of freshwater, when the glacial Lake Agassiz in North America burst its banks and poured into the North Atlantic and Arctic Oceans. This vast pulse, a greater volume than all of North America's Great Lakes combined, diluted the North Atlantic conveyor belt and brought it to a halt.
Without the warming influence of this ocean circulation temperatures across the Northern hemisphere plummeted, ice sheets grew and human civilisation fell apart.
Previous evidence from Greenland ice cores has indicated that this sudden change in climate occurred over the space of a decade or so. Now new data shows that the change was amazingly abrupt, taking place over the course of a few months, or a year or two at most.
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Looking ahead to the future Patterson says there is no reason why a 'Big Freeze' shouldn't happen again. "If the Greenland ice sheet melted suddenly it would be catastrophic," he says.
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http://www.msnbc.msn.com/id/34242705/ns/technology_and_science-science/
This kind of scenario would not discount evidence pointing toward global warming — after all, it leans on the Greenland ice sheet melting.
"We could say that global warming could lead to a dramatic cooling," Patterson told LiveScience. "This should serve as a further warning rather than a pass."
"People assume that we're political, that we're either pro-global-warming or anti-global-warming, when it's really neither," Patterson added. "Our goal is just to understand climate."
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At this point, I am not very optimistic that we humans will act wisely enough to avoid very bad results from global warming, but I certainly hope it is gradual enough to at least avoid stopping the North Atlantic conveyor belt. The article referenced below gives hope for that.
And if it does, that means that the heat from more southern areas would no longer be transferred from more southern areas to more northern areas, so those southern areas would become even hotter than otherwise.
http://www.sciencedaily.com/releases/2009/11/091127134037.htm
ScienceDaily (Dec. 4, 2009) — The Gulf Stream system is known for its impact on Europe's mild climate. For quite some time oceanographers and climate scientists worry that its strength could decline due to the climate change. Unexpected help could come from the ocean currents south of Africa: researchers of the Leibniz Institute of Marine Sciences (IFM-GEOMAR) and the University of Cape Town have discovered that the Agulhas Current transports more saline waters into the Atlantic. These could potentially contribute to stabilize the Gulf Stream system. The study will appear on 26 November in the scientific journals Nature.
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