Antarctic Ice Shelf Disappears, Arctic Melting Rapidly

The USGS study focuses on Antarctica, the Earth's largest reservoir of glacial ice. It shows that Antarctica's glaciers are melting more rapidly than previously known because of climate change.

"This study provides the first insight into the extent of Antarctica's coastal and glacier change," said U.S. Interior Secretary Ken Salazar. "The rapid retreat of glaciers there demonstrates once again the profound effects our planet is already experiencing — more rapidly than previously known - as a consequence of climate change."

"The scientific work of USGS, which is investigating the impacts of climate change around the world, including an ongoing examination of glaciers, is a critical foundation of the administration's commitment to combat climate change," Salazar said.

Antarctica's Larsen Ice Shelf is melting. (Satellite photo courtesy NASA)

Scientists previously knew that the Wordie Ice Shelf has been retreating, but this study documents for the first time that it has completely disappeared.

Moreover, the northern part of the Larsen Ice Shelf no longer exists. An area more than three times the size of the State of Rhode Island - more than 8,500 square kilometers - has broken off from the Larsen Ice Shelf since 1986.

USGS scientists report that these floating ice shelves are especially sensitive to climate change, so their rapid retreat may be a forecast for losses of the land-based ice sheet on the Antarctic continent if warming continues.

This could result in sea-level rise, threatening low-lying coastal communities and islands, they warn.

"This continued and often significant glacier retreat is a wakeup call that change is happening in our Earth System and we need to be prepared," said USGS glaciologist Jane Ferrigno, lead author on the study. "Antarctica is of special interest because it holds an estimated 91 percent of the Earth's glacier volume, and change anywhere in the ice sheet poses significant hazards to society."

The research in Antarctica is a collaborative effort of the USGS and the British Antarctic Survey, with the assistance of the Scott Polar Research Institute at the University of Cambridge and Germany's Bundesamt fur Kartographie und Geodasie.

An iceberg drifting in the Southern Ocean near Antarctica. (Photo © Ted Scambos courtesy National Snow and Ice Data Center)

The new report and map of the Larsen Ice Shelf are part of a project to research the coastal change and glaciological characteristics of the entire Antarctic coastline.

The research is also part of the USGS Glacier Studies Project that is monitoring and describing glacier extent and change over the whole planet using satellite imagery.

In a separate study published in today's issue of the journal "Geophysical Letters," the National Oceanic and Atmospheric Administration reports that summers in the Arctic may be ice-free in as few as 30 years, not at the end of the century as previously expected.

The updated forecast is the result of a new analysis of six computer models coupled with the most recent summer ice measurements from 2007 and 2008.

"The Arctic is changing faster than anticipated," said James Overland, an oceanographer at NOAA's Pacific Marine Environmental Laboratory and co-author of the study. "It's a combination of natural variability, along with warmer air and sea conditions caused by increased greenhouse gases."

The area covered by summer sea ice is expected to decline to about one-quarter of its present size - from its current 1.8 million square miles to about 390,000 square miles - a loss of two-fifths the size of the continental United States.

The NOAA team predicts that much of the sea ice would remain in the area north of Canada and Greenland and decrease between Alaska and Russia in the Pacific Arctic.

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