Monday, May 13, 2013

Ice-free arctic may be in our future

UMassAmherst Office of News & Media Relations: Analyses of the longest sediment core ever collected on land in the Arctic, recently completed by an international team led by Julie Brigham-Grette of the University of Massachusetts Amherst, provide “absolutely new knowledge” of Arctic climate from 2.2 to 3.6 million years ago and show that with estimated atmospheric carbon dioxide (CO2) similar to today’s levels, the Arctic was very warm, with no ice sheets.

“While existing geologic records from the Arctic contain important hints about this time period, what we are presenting is the most continuous archive of information about past climate change from the entire Arctic borderlands. As if reading a detective novel, we can go back in time and reconstruct how the Arctic evolved with only a few pages missing here and there,” says Brigham-Grette.

Results of analyses that provide “an exceptional window into environmental dynamics” never before possible were published this week in Science and have “major implications for understanding the pacing and context of how the Arctic transitioned from a forested landscape without ice sheets to the ice- and snow-covered land we know today,” she adds.

Their data come from analyzing sediment cores collected in the winter of 2009 from under ice-covered Lake El’gygytgyn, the oldest deep lake in the northeast Russian Arctic. “Lake E” was formed 3.6 million years ago when a huge meteorite hit the Earth and blasted out an 11-mile (18 km) wide crater. It has been collecting sediment layers ever since. Luckily for geoscientists, it lies in one of the few Arctic areas not eroded by continental glaciers, so a thick, continuous sediment record was left remarkably undisturbed. Cores from Lake E reach back in geologic time nearly 30 times farther than Greenland ice cores that cover the past 140,000 years.

“One of our major findings is that the Arctic was very warm in the Pliocene [~ 5.3 to 2.6 million years ago] when others have suggestedatmospheric CO2 was very much like levels we see today. This could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier models,” the authors state....

NASA image showing the location of Lake El'gygytgyn


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