September 14, 2012
Prehistoric Glaciers Reacted Rapidly To A Brief Cold Snap
April Flowers for redOrbit.com - Your Universe Online
New research, led by the University at Buffalo, is examining an important mystery surrounding climate change: How quickly do glaciers melt and grow in response to shifts in temperature.
According to the study, published in Science, glaciers on Canada's Baffin Island expanded rapidly during a brief cold snap about 8,200 years ago. This discovery adds to a growing body of evidence that shows ice sheets reacted rapidly in the past to cooling or warming, raising concerns that they could do so again as the Earth heats up.
"One of the questions scientists have been asking is how long it takes for these huge chunks of ice to respond to a global climate phenomenon," said study co-author Jason Briner, PhD, a University at Buffalo associate professor of geology. "People don't know whether glaciers can respond quickly enough to matter to our grandchildren, and we're trying to answer this from a geological perspective, by looking at Earth's history."
"What we're seeing," he added, "is that these ice sheets are surprisingly sensitive to even short periods of temperature change."
Baffin Island is in Canada's Nunavut territory, and is the largest island in Canada and fifth largest in the world. Most of Baffin Island lies above the Arctic Circle, so it has an extremely cold climate and sea ice surrounds the island most of the year.
The study found that mountain glaciers on Baffin Island, along with a massive North American ice sheet, expanded quickly when the Earth cooled about 8,200 years ago. The surprising part of this is that the cold snap was extremely short-lived. The temperatures fell for only a few decades, and then returned to "normal" levels within 150 years or so.
"It's not at all amazing that a small local glacier would grow in response to an event like this, but it is incredible that a large ice sheet would do the same," Nicolas Young, post-doctoral researcher at Columbia University's Lamont-Doherty Earth Observatory, said.
Briner, Young and an international team went to Baffin Island to read the landscape for clues about the pre-historical size and activity of glaciers that covered the island.
Piles of rock and debris deposited by glaciers as they expand, called moraines, provided valuable information. By dating these and other geological features, the team was able to deduce that glaciers expanded rapidly on Baffin Island about 8,200 years ago during that short cold snap.
They also found that Baffin Island's glaciers appear to have been larger during this brief period of cooling than during the Younger Dryas period, a much more severe episode of cooling that began about 13,000 years ago and lasted more than a millennium.
This counterintuitive finding suggests that unexpected factors may govern a glacier's response to climate change.
The team found that while overall cooling may have been more intense during the Younger Dryas, summer temperatures on Baffin Island may have actually decreased more during the shift 8,200 years ago. These colder summers could have fueled the glaciers' rapid advance, decreasing the length of time that ice melted during the summer.
Detailed analyses of this kind will be critical to developing accurate models for predicting how future climate change will affect glaciers around the world, Briner said.