Thirteen thousand years ago, an extreme cold snap cooled the Northern Hemisphere, ending more than 1,000 years of warming.
Known as The Younger Dryas — named after the flower Dryas octopetala that flourished in cold conditions — the cause of the sudden climate shift remained a mystery for decades.
A new study revealed the signs of a massive flood of fresh water in the western Arctic, which scientists believe to be the cause. Researchers involved in the study found that an inpouring of freshwater from melting glaciers in North America disrupted the North Atlantic Current, which flows between the equator, Europe and Canada.
“Even though we were in an overall warming period, this freshwater, exported from the Arctic, slowed down the vigor, efficiency of the meridional overturning, and potentially caused the cooling observed strongly in Europe,” Neal Driscoll, one of the study’s authors and a professor at the Scripps Institution of Oceanography, said.
The team of researchers from WHOI, Scripps Institution of Oceanography at the University of California San Diego, and Oregon State University, sailed in 2013 to the eastern Beaufort Sea in search of evidence for the flood near where the Mackenzie River enters the Arctic Ocean, between Canada's Yukon and Northwest territories. The team gathered sediment cores from along the continental slope east of the Mackenzie River, and analyzed the shells of fossil plankton within the sediment cores, finding the geochemical fingerprint from the flood.
Other findings revealed a narrative of the movement of water across the Arctic. As the ice age ended, the massive Laurentide ice sheet atop North America receded, its meltwater feeding the glacial Lake Agassiz, which stretched across much of Canada. From there, the new research shows, the fresh meltwater emptied into the Arctic Ocean through the Mackenzie River, the longest river system in Canada. This dump of fresh water into the Atlantic would have interfered with its circulation, setting the global stage for an extreme climate shift.
The results of the study, published in Nature Geoscience, highlight how influential the Arctic is on the world's climate. Lloyd Keigwin, head researcher and senior scientist at the Woods Hole Oceanographic Institution, warns that today’s melting Arctic ice could one day prompt a similar temperature snap. As the planet warms under human activity, and its ice melts, the oceans could see major changes that would interfere with the Atlantic circulation, which is crucial to the regulation of global temperatures.
Though the results of the study are still under debate, with some researchers arguing that a different flood event entered the ocean thousands of miles away, the key points are still relevant to understanding our current climate. Keigwin said it's possible melting ice in Greenland and the Antarctic today could one day prompt a similar climate shift.
"It's not just a dusty history," he said. "It's something very active, and it's happening today.”