Ice Shelves on Antarctic Peninsula Melting Away, USGS Reports

RESTON, Virginia, February 22, 2010 (ENS) – Ice shelves are retreating in the southern section of the Antarctic Peninsula due to climate change, the U.S. Geological Survey announced today in a new report. “This could result in glacier retreat and sea-level rise if warming continues, threatening coastal communities and low-lying islands worldwide,” warns the federal government’s largest water, earth, biological science and civilian mapping agency.

USGS research is the first to document that every ice front in the southern part of the Antarctic Peninsula has been retreating overall from 1947 to 2009, with the most dramatic changes occurring since 1990.

Map shows in blue the ice extent in 1947 between Charcot Island and the Wilkins Ice Shelf. The red line shows the ice shelf edge in 2009. (Map courtesy USGS)

“This research is part of a larger ongoing USGS project that is for the first time studying the entire Antarctic coastline in detail, and this is important because the Antarctic ice sheet contains 91 percent of Earth’s glacier ice,” said USGS scientist Jane Ferrigno.

“The loss of ice shelves is evidence of the effects of global warming,” she said. “We need to be alert and continually understand and observe how our climate system is changing.”

The USGS previously documented that the majority of ice fronts on the entire Antarctic Peninsula have also retreated during the late 20th century and into the early 21st century.

The ice shelves are attached to the continent and already floating, holding in place the Antarctic ice sheet that covers about 98 percent of the Antarctic continent.

As the ice shelves break off, it is easier for outlet glaciers and ice streams from the ice sheet to flow into the sea. The transition of that ice from land to the ocean is what raises sea level.

The Peninsula is one of Antarctica’s most rapidly changing areas because it is farthest away from the South Pole, and its ice shelf loss may be a forecast of changes in other parts of Antarctica and the world if warming continues, the USGS said.

Retreat along the southern part of the Peninsula is of particular interest because that area has the Peninsula’s coolest temperatures, demonstrating that global warming is affecting the entire length of the Peninsula.

The Antarctic Peninsula’s southern section as described in this study contains five major ice shelves – Wilkins, George VI, Bach, Stange and the southern portion of Larsen Ice Shelf. The ice lost since 1998 from the Wilkins Ice Shelf alone totals more than 4,000 square kilometers, an area larger than the state of Rhode Island.

The Wilkins Ice Shelf, on the western side of the Antarctic Peninsula, experienced multiple disintegration events in 2008. By the beginning of 2009, a narrow ice bridge was all that remained to connect the ice shelf to ice fragments fringing nearby Charcot Island. That bridge gave way in early April 2009.

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

Breakup of the Wilkins Ice Shelf, April 12, 2009 (Satellite photo courtesy NASA Earth Observatory)

The USGS is working collaboratively on this project with the British Antarctic Survey, with the assistance of the Scott Polar Research Institute and Germany’s Bundesamt fur Kartographie und Geodasie.

This week at the American Association for the Advancement of Science annual meeting in San Diego, marine biologist Huw Griffiths from the British Antarctic Survey presented research from the Census of Antarctic Marine Life describing how melting of the polar ice is changing the balance of animals in the Antarctic.

Populations of krill, the shrimp-like invertebrates eaten by penguins, whales and seals, are reducing as a result of a decrease in sea-ice cover. Much smaller crustaceans, called copepods, are dominating the area once occupied by them, explained Griffiths.

This shifts the balance of the food web to favor predators, like jellyfish, that are not eaten by penguins and other Southern Ocean higher predators. Sea-ice reduction is also affecting penguins that breed on the ice.

Griffiths says, “The polar regions are amongst the fastest warming places on Earth and predictions suggest that in the future we’ll see warming sea surface temperatures, rising ocean acidification and decreasing winter sea ice – all of which have a direct effect on marine life.”

“Marine animals spent millions of years adapting to the freezing, stable conditions of the Antarctic waters and they are highly sensitive to change. This means that from the scientist’s perspective they are excellent indicators of environmental change,” Griffiths said.

“The polar oceans are rich in biodiversity,” he said. “If species are unable to move or adapt to new conditions they could ultimately die out. The loss of any unique species is therefore a loss of global diversity.”

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