(First published on Feb. 14, 2017, on State of the Planet.)
Aaron Putnam sits atop a boulder high in the Sierras of central California, banging away with hammer and chisel to chip out a sample of ice age history. Each hunk of rock is a piece of a vast puzzle: How did our climate system behave the last time it warmed up like it’s doing today?
Filed under Climate, Science
The Rhone Glacier in 1900 and 2008. Residents of the village of Gletsch, down the valley from the glacier, have kept track of the ice since 1602. “Their water supply, the availability of farmland is controlled by where the glacier is,” researcher Brent Goehring said. (Photos: http://www.swisseduc.ch/glaciers/index-en.html)
First published on the Earth Institute’s State of the Planet blog on June 3, 2011
During the last ice age, the Rhone Glacier was the dominant glacier in the Alps, covering a significant part of Switzerland. Over the next 11,500 years or so, the glacier, which forms the headwaters of the Rhone River, has been shrinking and growing again in response to shifts in climate.
Until now, scientists have had no accurate way of knowing the long-term history of the glacier. Local records of the ice date back to 1602, and it is clear that the Rhone, like other glaciers in the Alps, has retreated dramatically in the past 150 years. This melting has exposed intriguing clues – remnants of trees from once-forested land, and artifacts of human settlements dating back thousands of years, to times when even more of the land was uncovered and green.
A team of researchers led by two scientists from the Lamont-Doherty Earth Observatory have found a novel method to measure this crucial back-and-forth, by measuring isotopes in hunks of stone chipped out from recently exposed bedrock near the edge of the ice. They found that for most of the Holocene Epoch, dating from the end of the last ice age about 11,500 years ago to the present, the Rhone Glacier has been smaller than it is today.