Researchers once believed that the melting was limited to the Antarctic Peninsula, a narrow tongue of land pointing toward South America. But satellite data and automated weather stations now indicate it is more widespread.
The melting "also extends all the way down to what is called west Antarctica," said Colin Summerhayes, executive director of the Britain-based Scientific Committee on Antarctic Research.
"That's unusual and unexpected," he told The Associated Press in an interview.
By the end of the century, the accelerated melting could cause sea levels to climb by 3 to 5 feet - levels substantially higher than predicted by a major scientific group just two years ago.
Making matters worse, scientists said, the ice shelves that hold the glaciers back from the sea are also weakening.
The report Wednesday from Geneva was a broad summary of two years of research by scientists from 60 countries. Some of the findings were released in earlier reports.
In Washington, as part of an overall update on global warming, top researchers on Wednesday sounded a similar warning to the U.S. Senate about rising temperatures in the Antarctic.
The head of the Intergovernmental Panel on Climate Change, a group set up by the United Nations, told lawmakers on the Environment and Public Works Committee that Earth has about six more years at current rates of carbon dioxide pollution before it is locked into a future of severe global warming.
For years, the continent at the bottom of the world seemed to be the only place on the planet not experiencing climate change. Previous research indicated that temperatures across much of Antarctica were staying the same or slightly cooling.
The report Wednesday was compiled as part of the 2007-2008 International Polar Year, an effort by scientists to conduct intense Arctic and Antarctic research over the past two Antarctic summers.
The big surprise was exactly how much glaciers are melting in western Antarctica, a vast land mass on the Pacific Ocean side of the continent that is next to the South Pole and includes the Antarctic Peninsula.
The biggest of the western glaciers, the Pine Island Glacier, is moving 40 percent faster than it was in the 1970s, discharging water and ice more rapidly into the ocean, said Summerhayes, a member of International Polar Year's steering committee.
The Smith Glacier, also in west Antarctica, is moving 83 percent faster than in 1992, he said.
The glaciers are slipping into the sea faster because the floating ice shelf that would normally stop them - usually 650 to 980 feet thick - is melting. And the glaciers' discharge is making a significant contribution to increasing sea levels.
Some people "fear that this is the first signs of an incipient collapse of the west Antarctic ice sheet," Summerhayes said. "If the west Antarctica sheet collapses, then we're looking at a sea level rise of between 3 feet, 4 inches, to nearly 5 feet."
Together, all the glaciers in west Antarctica are losing a total of around 114 billion tons per year because the melting is much greater than the new snowfall, he said.
"That's equivalent to the current mass loss from the whole of the Greenland ice sheet," Summerhayes said.
Looked at another way, it's more weight than 312,000 Empire State Buildings.
"We didn't realize it was moving that fast," he said.
Summerhayes said sea levels will climb higher than predicted by the Intergovernmental Panel on Climate Change,
A 2007 report by the IPCC predicted a sea level rise of 7 to 23 inches by the end of the century, which could flood low-lying areas and force millions of people to relocate.
The group said an additional 3.9- to 7.8-inch increase in sea levels was possible if the recent, surprising melting of polar ice sheets continues.
New research published this month in the journal Geophysical Research Letters found that melting glaciers will add at least 7 inches to the world's sea level - and that's if carbon dioxide pollution is quickly capped and then reduced.
Far more likely is an increase of at least 15 inches and probably more just from melting glaciers, the journal said.
Until recently, scientists debated whether Antarctica was warming.
But a January study in the journal Nature found that Antarctica's average annual temperature has increased by about 1 degree Fahrenheit since 1957, but is still 50 degrees below zero.
The report also determined that autumn temperatures in east Antarctica were cooling over the long term.
International Polar Year researchers found that the southern ocean around Antarctica has warmed about 0.36 degrees Fahrenheit in the past decade, double the average warming of the rest of the Earth's oceans over the past 30 years.