Big Freeze Triggered by Flood Path Reckon Climate Scientists
Scientists have come up with an explanation for the 1200-year-long ice up also called the big freeze, the last major cold age on Earth.
Geo scientist Alan Condron of the University of Massachusetts Amherst, along with Peter Winsor at the University of Alaska, have concluded that a climate-cooling period known technically as 'Younger Dryas' or just 'Big Freeze', occurred after glacial Lake Arassiz, at the southern edge of the Laurentide ice sheet covering Hudson Bay and much of the Canadian Arctic broke through an ice dam and pumped in thousands of cubic miles of fresh water into the ocean.
"This episode was the last time the Earth underwent a major cooling, so understanding exactly what caused it is very important for understanding how our modern-day climate might change in the future," says Condron.
The flood flowed north into the Arctic down the Mackenzie River valley first. Had it flown the other way, the study shows that the climatic conditions would have been relatively unchanged.
This gushing of fresh water is assumed to have altered the density of the Northern Atlantic colder water that in turn affected large scale ocean circulation, called the "Thermohaline circulation," of heat waves over the oceans in Europe and North America.
The weakening of this circulation caused by flooding resulted in the big freeze in North America and Europe.
Condron and Winsor designed a high resolution ocean-ice circulation model and took cues from the original hypothesis proposed in 1989 by Wally Broecker of Columbia University suggesting that Lake Aggasiz drained into the North Atlantic down the St. Lawrence River. According to the researchers this would have weakened the thermohaline circulation by less than 15 percent.
Their study suggests that the weakening of the circulation of heat waves was unlikely to have accounted for the 1,000-year cold climate. Melted water from St. Lawrence River ended up roughly 1,900 miles south of deep waters. It is quite far south to have any significant impact on the sinking of surface waters. This suggests that the melted waters had a minor impact on thermohaline circulation.
Condron and Winsor's model shows that when melted water first drained into the Arctic Ocean, coastal currents delivered it to the deep water formation regions of the sub-polar north Atlantic, weakening the thermohaline circulation by 30 percent. Scientists concluded that the flood water gushed into the Arctic first, rather than the St. Lawrence valley.
''With this higher resolution modeling, our ability to capture narrow ocean currents dramatically improves our understanding of where the fresh water may be going.'' Allan Condron.
Their research model is based on data computed using world's top super computer at the National Energy Research Computing Center in Berkeley, California.
Condron also adds, "The results we obtained are only possible by using a much higher computational power available with faster computers. Older models weren't powerful enough to model the different pathways because they contained too few data points to capture smaller-scale, faster-moving coastal currents."
"Our results are particularly relevant for how we model the melting of the Greenland and Antarctic Ice sheets now and in the future. It is apparent from our results that climate scientists are artificially introducing fresh water into their models over large parts of the ocean that freshwater would never have reached. In addition, our work points to the Arctic as a primary trigger for climate change. This is especially relevant considering the rapid changes that have been occurring in this region in the last 10 years," he says.