Glaciers Experience Shrinkage
21 Apr 2005
Antarctic Peninsula glaciers are in retreat, according to the first comprehensive survey of the continent’s largest peninsula.
The effect parallels the rise in air temperatures on the peninsula over the same period and hints at what might happen to glaciers elsewhere if the world continues to warm.
The Antarctic Peninsula, the continent’s long arm that reaches out toward Chile, has long been a focus of climate research. While the world warmed, on average, by about 0.6°C over the 20th century, temperatures on the peninsula rose 5 to 10 times that fast. People stationed there reported that glaciers’ leading edges, which float in the ocean, were shrinking back. But the scope of the situation was unclear.
The new survey turns those anecdotes into quantifiable fact, says study co-author David Vaughan, a glaciologist at the British Antarctic Survey in Cambridge, United Kingdom. The survey’s team tracked the movement of 244 marine glaciers on the peninsula by examining aerial photographs dating back to the 1940s, as well as more recent satellite images. The researchers found that, from 1944 to 1954, roughly two-thirds of the glaciers in the study were advancing. The glacier shrinkage began first at the northern tip of the peninsula in the mid-1950s. Then as the decades progressed, glaciers farther southward began to shrink too. Now about three-quarters are in retreat, a complete about-face from 50 years ago.
Increases in average air temperature seem partly responsible for the glacial retreat but can’t account for all of it, says Vaughan. “We’ve looked quite hard at several variables, but we can’t produce a model that reproduces the change,” he says. The authors, who report their results 22 April in Science, suggest that the loss of ice from the fronts of the glaciers could mean the peninsula is dumping more ice into the ocean than previously thought.
“This is a clear record of glaciers showing effects of climate change,” says Theodore Scambos, a glaciologist at the National Ice and Snow Data Center at the University of Colorado, Boulder. “And using old data to extend that record back—that’s impressive.”