Skip to comments.Broken Ice Dam Blamed For 300-Year Chill
Posted on 01/10/2006 2:47:01 PM PST by blam
Broken ice dam blamed for 300-year chill
14:21 10 January 2006
NewScientist.com news service
A three-century-long cold spell that chilled Europe 8200 years ago was probably caused by the bursting of a Canadian ice dam, which released a colossal flood of glacial meltwater into the Atlantic Ocean.
Two new papers, using different computer models, show that the massive freshwater flood accounts for evidence of the sudden climate change, which cooled Greenland by an average of 7.4°C, and Europe by about 1°C. It was the most abrupt and widespread cool spell in the last 10,000 years.
Evidence for the cooling has been found in ice core samples, preserved pollen, evidence of shifting lake levels and ocean sediment. Some researchers think the cooling might have been caused by normal fluctuations in solar radiation.
In 1999 Don Barber, a geologist now at Bryn Mawr College in Pennsylvania, US, and colleagues suggested that the cooling was caused by flooding by glacial meltwater. Geological evidence shows that by about 11,000 years ago, retreating glaciers had left two huge freshwater lakes sprawling over Central Canada and parts of the northern US, bigger than all of today's Great Lakes combined.
Eventually, the lakes broke through an ice sheet that served as a dam and drained into Hudson Bay, and from there into the North Atlantic (Nature, vol 400, p 344).
Barber's idea was that the influx of fresh water changed salinity levels in the North Atlantic, and disrupted the thermohaline circulation the currents that bring warm southern water north, helping to warm Europe and the Arctic regions.
In the new papers, one in the Proceedings of the National Academy of Sciences and the other in the current Quaternary Science Reviews, two teams of researchers using different computer models say that both models show that such a freshwater flood could shut down ocean circulation in a way that is consistent with temperature data from the time.
"We've shown the hypothesis generates the climate change that generates the data. It makes the story of the 8200-year event a much more well-rounded story," says Gavin Schmidt, a climatologist at NASA's Goddard Institute for Space Studies in New York City, US, a co-author of the PNAS paper.
"I would say it's a pretty strong confirmation of our understanding of that event," says Barber.
The work could have implications for the modern climate. Some researchers suggest that global warming and glacial melting might one day change ocean salinity enough to cause a similar disruption in ocean currents.
Journal references: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0510095103), Quaternary Science Reviews (vol 25, p 63)
They say the water broke out to the north rather than down the St Lawrence and Mississippi. Is that what you get from this?
But they were 'Sport Utility Ice Dams'.
I believe this period is known as the Older Dryas.
I like how the author slipped in the "global warming" comment. Jeez.
Oh no! A whole degree cooler!
Yes and that could make sense too.
The evidence for this type of event was found out along the continental shelf off the coast of New Jersey, in the form of large rocks scattered on the ocean floor that are indigenous to the Adirondack Mountains -- hundreds of miles away from the mouth of the Hudson River.
"We shoulda signed the Kyoto Treaty!"
Was global warming or global cooling associated with the Ice Age? Could it not have been more of a regional phenomenon?
Just like the History Channel's show on the "little ice age" that was on this past Sunday. Interesting show, but the political agenda revealed at the end called into question everything that had previously been said.
Three words: Rove, Cheney & Bush!
and of course the Hudson canyon remains today under the ocean wending along.......a trench that goes hundreds of miles out into the Atlantic before it ends at the dropoff of the continental shelf.
The fault of Bush's environmental policies.
Yes. They were dammed up and broken a couple times. The biggest flood went north into the Hudson Bay...the ice sheet that was on the largest lake, became boyant, broke and slid into Hudson Bay causing gawd awful tsunamis.
Once this 'chill' period was over, the Ice Age melt resumed unhindered.
It was just after this period that the Mediterranean reflooded and eventually broke the dam at the Bosporus and flooded the Black Sea.(Noah's Flood?)
I saw some of that and found it quite interesting. I guess I am fortunate I missed the ending.
There's alot of interesting geology in New York. There is a place near where I grew up where the shale bedrock is exposed, and you can see the grooves cut in the rock from the glaciers.
Alot of New York was at one time, submerged. Some of the largest salt deposits in the world are buried in the western part of the state.
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