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
The Pilgrims Were Definitely Not Like Modern-Day Refugees
This upcoming Thanksgiving Day is sure to offer you and your family plenty of opportunities to argue over whether America should be welcoming Syrian refugees.
If you have any liberal relatives or friends coming over for your Thursday feast, theyâ€™re going to relish the chance to tell everyone that the Pilgrims were refugees too â€” and hope that statement decimates all ...
ISIS to France: "We will be coming. Victory has been promised to us by Allah"
Homegrown French ISIS fighters have issued a chilling threat of new attacks on France just 24 hours after the terrorist group used movie footage of the Eiffel Tower's collapse in another video.
A balaclava-clad militant is seen warning 'we will be coming, we will come to crush your country' in footage posted on Twitter earlier today.
It is unclear where the film ...
ISIS teenage 'poster girl' Samra Kesinovic 'beaten to death' as she tried to flee the group
She appeared in social media images for the group carrying a Kalashnikov and surrounded by armed men
A teenage girl who ran away from her Vienna home to join Isis in Syria has reportedly been beaten to death by the group after trying to escape.
Samra Kesinovic, 17, travelled to Syria last year with her friend Sabina Selimovic, 15.
The two became a ...
The Right Stuff's flagship podcast "The Daily Shoah" has been censored by Soundcloud
Editor's note: The PC corporate moral police strike again. Just as Radio 3Fourteen & Red Ice Radio were censored from iTunes, The Daily Shoah was pulled from Soundcloud today. As per usual, there is a double standard, they allow any kind of anti-White material:
No counter culture humor making fun of the genocidal mainstream garbage is allowed!
Soundcloud took it upon ...
Merkel Welcomes A Million More: Vows To Stand By Refugee Policy Despite Security Fears
Chancellor Angela Merkel vowed on Wednesday to stick to her open-door refugee policy, defying criticism at home and abroad which has intensified due to growing fears about a potential security risk after the Islamist attacks in Paris.
Conservative Merkel faces splits in her right-left coalition and pressure from EU states, including France, over her insistence that Germany can cope with up ...
|More News » |