Ice cores from arctic mountain glaciers show a dramatic climate change that began nearly 300 years ago, documenting an unprecedented increase in the intensity and duration of winter storms. Drilled by a Dartmouth-led team, the cores show striking changes in weather patterns that may have reached as far as Florida.
“We attribute these changes to a warming of sea surface temperatures in the tropical Pacific,” says Erich Osterberg, an assistant professor in the Department of Earth Sciences at Dartmouth. “The North Pacific is very sensitive to what happens in the tropics. It is more stormy in Alaska now than at any time in the last 1,200 years, and that is driven by tropical ocean warming.”
Ice cores from arctic mountain glaciers show a dramatic climate change that began nearly 300 years ago, documenting an unprecedented increase in the intensity and duration of winter storms. Drilled by a Dartmouth-led team, the cores show striking changes in weather patterns that may have reached as far as Florida.
“We attribute these changes to a warming of sea surface temperatures in the tropical Pacific,” says Erich Osterberg, an assistant professor in the Department of Earth Sciences at Dartmouth. “The North Pacific is very sensitive to what happens in the tropics. It is more stormy in Alaska now than at any time in the last 1,200 years, and that is driven by tropical ocean warming.”
The cores, two sets drilled in parallel at Mount Hunter in Alaska’s Denali National Park and another from the summit of Mount Logan in Canada’s Yukon, measure more than 600 feet in depth and depict more than a thousand years of climate history in the North Pacific. Denali and Mount Logan are the first- and second-highest mountains in North America.
“If you can show the same phenomenon in two different cores, or ideally three or more, then you have a lot more confidence in your results,” says Osterberg. “It is not just restricted to one small region, say, Denali, and it’s not the result of some error in our analysis. We are melting ice and then chemically analyzing it, and interpreting that in terms of climate. Any time we have these types of climate proxy records, we like to see a common signal in more than one record.”
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Photo: Annual rings can be seen in a core from deep in Alaskan glacial ice.
(Photo Courtesy of Erich Osterberg)
