ScienceNOW - Younger Dryas Cooling May Have Happened In 1 Year - Study Challenges Halocline Collapse

[hatrack]

It sounds like the stuff of science fiction, but nearly 13 millennia ago Europe was plunged suddenly into a deep freeze that lasted 1300 years--and the change happened in little more than a year, according to new data. The evidence also suggests that strong winds, not ocean currents, drove the rapid climate change.

Soon after the end of the last ice age, some 12,700 years ago, Europe suddenly fell into another perpetual winter. Average temperatures on the continent plunged as much as 5°C, and global temperatures overall dropped about 3°C. This extended cold period is known as the Younger Dryas, and paleoclimatologists studying Greenland ice cores and other evidence have known for some time that it began quickly, perhaps within just decades. But until now no one was sure exactly how rapidly the climate had changed or why. One hypothesis was a sudden shift in--or even a shutoff of--the Atlantic Ocean current that brings warm water from the tropics to Western Europe and helps the present-day continent maintain its relatively moderate temperatures.

Paleoceanographer Gerald Haug of the Geological Institute in Zürich, Switzerland, and colleagues hunted for clues in sediments from Lake Meerfelder Maar in western Germany. Nestled inside an ancient volcanic crater, the lake is the only place known to hold well-preserved sediments that span the Younger Dryas. The fine-grained layers even reveal seasonal changes.

In particular, the team studied deposits of siderite, a mineral formed by microscopic lake plankton during relatively warm months. Using x-ray scanning techniques to examine the deposits, the researchers found that, after several hundred years of seasonal changes, the siderite production stopped abruptly. "It gave us quite a surprise," Haug says. That suggests that the Younger Dryas began within a single year, the researchers report in the August issue of Nature Geoscience.

EDIT

http://sciencenow.sciencemag.org/cgi/content/full/2008/805/3

[kestrel91316]

1. And everybody was laughing at Art Bell and Whitley Strieber

and The Day After Tommorow..........

[xchrom]

2. if that current shuts off again -- and

there is concern that it may well for reasons related to global warming -- this weather change in europe may return.

certainly england will feel some severe effects.

[Warpy]

3. Yet the Younger Dryas wasn't an unmitigated catastrophe

as it coincides with a wetter period in what's now the desert southwest and was the same period during which the Clovis people appeared. When the Younger Dryas ended, the Clovis people disappeared.

What seems certain is that dramatic climate shifts have happened in the past and will likely happen again in the future.

Linking it to a persistent change in wind patterns is a new one, though.