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.