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A giant overflow of Arctic meltwater may have triggered an ancient 1,200 - year - long chill nicknamed the " Big freezing , " the last major cold eld on Earth , a Modern study finds .
These findings hint that modification in the catamenia of water in the Arctic could suddenly change the modern climate , study investigators added .
The drainage pathways of meltwater stored in glacial lakes located along the southern margin of the Laurentide Ice Sheet. The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue).
Starting about 12,900 years ago , the Northern Hemisphere was abruptly gripped by centuries of coldness , an era technically live as the Younger Dryas . scientist have suggested this shivering help wipe out most of the large mammal in North America as well as the so - called Clovis multitude . The Big Freeze was not a glacial flow , which are conversationally often called methamphetamine hydrochloride age — it was a cold time in the comparatively strong duad between glacial stop .
Although researchers have suggesteda cosmic impact might have go down off this Big Freeze , the prevail hypothesis for the campaign of the Younger Dryas wasa vast heartbeat of fresh water — a nifty book than all of North America ’s Great Lakes combined — that poured into the Atlantic and Arctic Oceans . The author of this flood tide was apparently the glacial Lake Agassiz , locate along the southern security deposit of the Laurentide Ice Sheet , which at its maximal 21,000 days ago was 6,500 to 9,800 feet ( 2,000 to 3,000 meters ) thick-skulled and handle much of North America , from the Arctic Ocean in the south to Seattle and New York .
" The flood was likely triggered by the sudden breaking of an ice dekametre , " said researcher Alan Condron , a physical oceanographer at the University of Massachusetts at Amherst . " Prior to the flood , meltwater is thought to have drained into the Gulf of Mexico , down the Mississippi River . After the dam broke , the water quickly flowed into the sea via a different river drainage organization . " [ 7 means the Earth Changes in the Blink of an Eye ]
The drainage pathways of meltwater stored in glacial lakes located along the southern margin of the Laurentide Ice Sheet. The direction of meltwater drainage is shown by the yellow arrows. The approximate position of the ice sheet is shown (in white) just before the onset of the Younger Dryas. The ocean colors are surface salinity from the control integration with warm (cold) surface currents shown in red (blue).
Altered circulation
This deluge would have thin the circulation of saltwater in the North Atlantic , disrupting theocean " conveyer belt . “that cycles warm H2O up to the Arctic , where it cools and sink and move around back south along the sea floor . With less warm brine be active poleward , temperature across the Northern Hemisphere apparently plunge .
The waters from Lake Agassiz were originally suggest more than two decades ago to have poured through the Great Lakes and St. Lawrence Valley . However , scientist lately suggested this meltwater may have instead flooded into the Arctic Ocean via the Mackenzie Valley about 2,500 mi ( 4,000 klick ) northwest of the St. Lawrence outlet .
To see which inundate waterway might well explain the plummeting temperatures seen during theYounger Dryas , a grouping of scientists developed computer mannikin that studied the encroachment meltwater from the two outlets had on the conveyer belt of electric current known as the Atlantic Meridional Overturning Circulation .
The researchers found that meltwater flood the St. Lawrence Valley would have weakened this stream in this transporter belt by 15 percent or less . In contrast , fresh water pour out into the Mackenzie Valley would have weaken this conveyer whack by 30 percent or more . This suggest the Mackenzie Valley was the likely path for the freezing find during the Younger Dryas , not the more southerly St. Lawrence Valley path .
" It is only by simulating the circulation of the sea at 10 to 15 times the resolution antecedently attain by modeller that we have been able to accurately capture the pathway that the meltwater would have taken in the ocean , " Condron secern OurAmazingPlanet .
Modern - daylight climate
The ocean apparently circulates in such a means that fresh water released farther northward near the Arctic can much more easily interrupt the sinking of surface body of water in the Greenland and Labrador Sea that set the tempo of the Atlantic Meridional Overturning Circulation .
" In line , when the meltwater enter the ocean from the Gulf of St. Lawrence , ocean currents stimulate it to be confined largely to the sub - tropical North Atlantic about 3,000 kilometers ( 1,800 nautical mile ) south of the Greenland and Labrador Seas , " Condron said . " As a solution , it has little encroachment on the strength of the Atlantic Meridional Overturning Circulation , and therefore on climate . "
These findings suggest that break in the flow of weewee in the Arctic could dramaticallyalter today ’s climate .
" However , in our modern - day clime , there are no rootage of fresh water as large as the frigid lakes or Laurentide Ice Sheet readily available to suddenly swamp into the ocean , " Condron said . " As a resultant role , we should be cautious using this cogitation as an analog for what might trigger advanced - day abrupt climate change . "
The researchers are now using their high-pitched - result model " to understand the sensitivity of our modern - day clime to increases in the melting of thelarge ice bed sheet over Greenlandand changes in the hydrological cycle , such as increased river overflow of the Arctic in the close - time to come , " Condron said .
Condron and his colleague Peter Winsor detailed their findings online Nov. 5 in the journal Proceedings of the National Academy of Sciences .
