Global warming has accelerated the melting of two Antarctic ice shelves, which lost nearly 1,200 square miles of area in the last year, U.S. and British researchers say.
Researchers at the University of Colorado and the British Atlantic Survey in Cambridge say regional warming has increased the annual melt season by up to three weeks over the past two decades, putting the Larsen B and Wilkins shelves on the Antarctic Peninsula in "full retreat."
Ice shelves are floating plates of ice that are still attached to continents, which form when large glaciers flow toward the ocean in polar areas.
Satellite photos show the Larsen B ice shelf has continued to crumble after an initial small retreat in the spring of 1998, the researchers said Wednesday. Since November, another 660 square miles of shelf area caved away.
On the other side of the peninsula, the Wilkins ice shelf retreated nearly 420 square miles in early March 1998, said Ted Scambos, a research associate at the University of Colorado at Boulder's National Snow and Ice Data Center.
"The radar images showed a large area of completely shattered ice, indicating an ice front 35 kilometers (21 miles) back from its previous extent," said Scambos.
He said thousands of small icebergs had appeared, suggesting "that the shelves are essentially broken up in place and then flushed out by storms or currents afterward."
David Vaughan, a researcher with British Antarctic Survey, said ice shelves in the area have been in retreat for 50 years but those losses have only included about 2,700 square miles.
"Within a few years, much of the Wilkins ice shelf will be gone," he said.
But Vaughan said the meltdown has few implications for the environment. Birds and animals are not known to rely on the ice shelves and there would be no increase in sea levels "because an ice shelf is floating anyway."
Since the 1940s, British researchers have reported an increase in mean annual temperature in the Antarctic of 4.5 degrees Fahrenheit. Summer temperatures now approach, and sometimes exceed 32 degrees Fahrenheit.
Larsen B is about 2,700 square miles, the size of Delaware. Wilkins is nearly twice that size.