Between 1996 and 2006, the amount of water lost from Greenland's ice sheet has more than doubled from 90 cubic kilometres to 220 cubic kilometres a year, Eric Rignot from NASA's Jet Propulsion Laboratory and the California Institute of Technology said.
"One cubic kilometre is the amount of water Los Angeles uses in a year. Two-hundred cubic kilometres of water is a lot of fresh water," Mr Rignot said.
The results could mean ocean levels will rise even faster than previously thought.
"Greenland is probably going to contribute more and faster to sea level rise than predicted," Mr Rignot told a press conference.
Mr Rignot and Pannir Kanagaratnam of the University of Kansas used satellite data to track the movement of Greenland's glaciers, which slide slowly down to the sea and deposit ice.
Since 1996, southeast Greenland's outlet glaciers have been flowing more quickly and since 2000 glaciers farther north have also sped up.
One glacier that once was stable is now disappearing at the rate of 14 kilometres a year, Mr Rignot said.
"It takes a long time to build and melt an ice sheet, but glaciers can react quickly to temperature changes," he added.
Warm air likely cause
Over the past 20 years, the air temperature in southeast Greenland has risen by three degrees Celsius, and the researchers report in the journal Science that the rising surface air temperature appears to be to blame.
"This is clearly a result of warming around the periphery of Greenland," Mr Rignot said.
Warmer air lubricates the bottoms of glaciers, helping them slide faster.
"Climate warming can work in different ways, but generally speaking, if you warm up the ice sheet, the glacier will flow faster," said Mr Rignot.
And the glaciers may melt even more quickly in the years to come, he added.
"The southern half of Greenland is reacting to what we think is climate warming. The northern half is waiting, but I don't think it's going to take long," Mr Rignot said.
The study did not explore what is causing the rising air temperatures in Greenland, but most scientists agree that human activity, and burning fossil fuels, is playing an important role in global warming.
Rising sea levels
The new figures have changed models scientists used to predict sea levels, with Greenland now calculated to contribute 0.5 millimetres, or one-sixth, of the annual global sea level rise of three millimetres.
Greenland’s overall ice mass is almost the size of Mexico, 1.7 million square kilometres, and if it all melted into the sea, ocean levels would rise by some seven metres.
Increased snowfall
Mr Rignot and other researchers noted that in some parts of Greenland, increased snowfall is making parts of some glaciers thicker.
"A few years back, we thought ice sheets might grow because of increased precipitation," Rignot said.
"Now we see that rates of glacier flow are changing. We think the process that is winning overall is the rate of glacier flow."