In another case of our pre-history helping us make sense of our future, researchers have definitively confirmed what shut down the Gulf Stream some 10,000 years ago. In a tale that reads like something out of Lord of the Rings, this catastrophe might have lessons for our future.
It was almost 10,000 years ago, and it was the end of the last ice age and the North American Laurentide ice sheet that covered most of Canada and a large majority of the Northern United States was slowly retreating, making its way back north.
As it slowly made its way back north, leaving behind newly shaped lands, it also left large amounts of fresh water. Much of this water formed an inland sea, where the Great Lakes now preside. This inland sea is also the precursor of the Great Lakes, but what came first is of more importance.
The massive lake burst its borders, emptying down the Hudson Strait and right in to the Labrador Sea west of Greenland. The major problem was that this great body of fresh water emptied in to an area of the ocean which is an important part of the Gulf Stream, where the Atlantic waters which are brought north are frozen and the leftover saline heavy water falls to the bottom.
The influx of such a large amount of low saline water choked the system, and halted the Gulf Stream altogether.
Europe immediately suffered what is now known as the Younger Dryas,
or the Big Freeze. Greenland ice-cores which have recently been
excavated show that in that area plummeting by up to 8 °C.
Until now, the above story has been much speculation, and little proof. But now Helga Kleiven and colleagues at the University of Bergen in Norway have discovered that this is exactly what happened, thanks to new studies conducted on the floor of the Labrador Sea.
A detailed study was carried out on sediments found on the sea floor, and found that there were sudden and dramatic changes at the time that the lake emptied. Included in these ‘changes’ was a flood of fine sediment from the land, which coincided with a large and quick drop in the amount of particles of magnetite, which are normally carried to the area by deep ocean currents. The changes happened within a decade or so, and were found to have happened in a warm climate, not dissimilar to those of today.
Mentioned at the top was the promise of lessons today.
The reason that we need these lessons is because although in a slower
fashion, the same thing is happening.
Great chunks of ice are braking off of Greenland instead of a steady
melt. These icebergs are increasing the amount of freshwater found
in the North Atlantic. Oceanographers believe that this may eventually
lead to another shutdown of the Gulf Stream, leaving Europe in a pocket
cold spot, while the rest of the planet warms.
Researchers now believe that the historical findings may help determine how much freshwater is needed to shut down the Gulf Stream. Hopefully, with a continual influx of new evidence such as this, further steps can be taken to reduce the likelihood of such an event reoccurring.
Posted by Josh Hill.
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