Ancient flood brought Gulf Stream to a halt
By Fred Pearce | newscientist.com
It was the biggest climate event of the last 10,000 years and caused the most dramatic change in the weather since humans began farming. And it may yet hold important lessons about climate change in the 21st century.
Just over 8000 years ago, a huge glacial lake in Canada burst, and an estimated 100,000 cubic kilometres of fresh water rushed into the North Atlantic. Researchers now say they know for sure that this catastrophic event shut down the Gulf Stream and cooled parts of the northern hemisphere by several degrees for more than a hundred years.
They say the findings show modelling studies are right to suggest that something similar could happen with equal abruptness as the planet warms under human influence. The film The Day After Tomorrow, which portrays such a scenario, may have exaggerated but not by much.
Lake Agassiz was a giant lake that formed at the end of the last ice age as the huge Laurentide ice sheet melted (see a simulation of the process Video). The lake occupied most of the modern-day Canadian Midwest between the Hudson Bay and the US border.
Climate historians have previously established that the lake burst suddenly, emptying down the Hudson Strait and into the Labrador Sea west of Greenland.
This is very close to a key point in the global ocean circulation system, where Atlantic water brought north on the Gulf Stream freezes, and dense, saline, leftover water plunges to the ocean floor.
Investigators have speculated that the huge slug of water from the emptying lake could have refreshed the ocean water so much that this plunging ceased, shutting down the circulation, including the Gulf Stream, which keeps countries around the North Atlantic warm.
That, they said, would explain why Greenland ice cores show temperatures in the area plummeting by up to 8 °C.
Now Helga Kleiven at the University of Bergen in Norway and colleagues claim to have found proof that this is exactly what happened.
They carried out a detailed study of sediments on the floor of the Labrador Sea and found clear signs of major changes exactly when the lake emptied and the temperatures dropped.
The changes include a flood of fine sediment from the land, coinciding with a sharp drop in the amount of particles of magnetite normally carried to the area by deep ocean currents. The study also shows that the changes were abrupt, happening within a decade or so, in warm climate conditions not unlike those of today.
Modern concerns arise because melting ice, especially on Greenland and in Siberia, is making the North Atlantic less saline. Oceanographers worry that this might eventually be sufficient to shut down the ocean circulation, says Kleiven, just as happened 8000 years ago, "particularly given the concerns about the impact of future warming on the Greenland ice sheet."
The next step, Kleiven believes, is to use the findings to work out exactly how much freshwater may be needed to shut down the circulation.
Article from: http://environment.newscientist.com/article/dn13013-
Earth's rotation can lead to the Deluge
Solar Storm Warning 2011-2012
Facing a world of fire and ice
Latest News from our Front Page
Better Identification of Viking Corpses Reveals: Half of the Warriors Were Female
Shieldmaidens are not a myth! A recent archaeological discovery has shattered the stereotype of exclusively male Viking warriors sailing out to war while their long-suffering wives wait at home with baby Vikings. (We knew it! We always knew it.) Plus, some other findings are challenging that whole ârape and pillageâ thing, too.
Researchers at the University of Western Australia decided ...
Off Your Knees, Germany! Ernst Zundel 1983 - 2003
For more information on the holocaust, how the war was forced upon Germany, and the REAL victims of the second world war see:
IRS Drops Attack For Six Years â No Evidence of Jurisdiction
A big congrats to a friend Iâve been working with for several years, he stood up to the predators commonly called the âIRSâ and they dropped their attack. Thanks also for providing me with the proof below.
The criminals called the âIRSâ initiated an attack claiming my friend was required to file six tax returns, or explain how he made ...
Into Eternity - Finland's 100,000 Year Massive Underground Spent Nuclear Fuel Program
Into Eternity is a documentary about a deep geological repository for nuclear waste. The concept of long-term underground storage for radioactive waste has been explored since the 1950s. The inner part of the Russian doll-like storage canisters is to be composed of copper. Hence in the case of Onkalo it is tightly linked to experiments on copper corrosion in running ...
SPLC Accuses Oath Keepers of Inciting âArmed Confrontationâ Over Sugar Pine Mine
The Southern Poverty Law Center has accused Oath Keepers of inciting an armed confrontation with BLM authorities over the Sugar Pine Mine dispute in Oregon, despite the fact that the organization has explicitly stated that it is not promoting armed confrontation with the feds.
In an article provocatively posted on the organizationâs âHatewatchâ section entitled Oath Keepers Descend Upon Oregon with ...
|More News » |