Patagonian Glaciers Thinning at Torrid Pace

A new study shows the great glaciers of the Patagonian ice fields between Chile and Argentina have retreated twice as fast in recent years as they did a quarter-century ago.

The area, home to the largest collection of Southern Hemisphere ice outside of Antarctica, has been little studied because of its forbidding location in the Andes between rough Chilean fiords and harsh deserts. Heavy cloud and snow cover has made the area difficult to survey with satellites and planes.

A team led by Eric Rignot of NASA’s Jet Propulsion Laboratory compared sparse data collected on past expeditions to the ice with precision topographical information obtained during a 2000 space shuttle mapping mission. The team found the glaciers were retreating and thinning much faster than expected and at a rate that could not be explained solely by the rising temperatures and decreased precipitation seen in the last half-century.

Rignot and his Chilean colleagues theorize that “ice dynamics” are playing a role in the rapid retreat, and that calving glaciers that break off over water, as opposed to land, retreat even faster once the water beneath them deepens.

The new work, published in the current issue of Science, could help predict the future behavior of glaciers in other parts of the world, including Greenland and Antarctica. The loss of ice in those regions could raise sea levels and cause flooding in low-lying parts of the world.

The loss of ice in Patagonia, as with much of the ice retreating worldwide, is largely a response to natural warming that has occurred since the end of the Little Ice Age more than a century ago. But the rate of ice loss seems to be accelerating with time, suggesting that more recent climate changes or unknown ice dynamics may play a role as well, Rignot said.