Greenland's glaciers are hemorrhaging ice at an increasingly faster rate but not at the breakneck pace that scientists once feared, a new study says.
The loss of ice from the glaciers that cover the island is about 30 percent faster than it was a decade ago, researchers said. That means Greenland's contribution to future sea level rise would be about 4 inches by the year 2100 if ice loss doesn't speed up much more, a study author said.
That may not sound like much, but when other causes of sea rise around the globe are added, the total could still be about 3 feet by the end of the century, researchers said.
"'Glacial pace' is not slow anymore," said study author Twila Moon, a glacier researcher at the University of Washington.
At the same time, "some of the worst-case possibilities that we had imagined are not coming true at this point," Moon said. "So it's not good news, but it's not bad news."
The scientists relied on a comprehensive satellite-based survey of about 200 glaciers to make their calculations. Their research was published Thursday in the journal Science.
Compared to some past research the findings are somewhat reassuring. A 2008 study had suggested a worst-case scenario that indicated Greenland's glaciers might contribute up to 19 inches of sea rise by the end of the century.
The glaciers have been melting under warmer summer temperatures in Greenland that on average are up by about 2 degrees Fahrenheit (1 degree Celsius) over the last decade, study authors said.
One famous glacier on northwestern Greenland called Jakobshavn is now losing ice at a particularly fast pace of 7 miles (11.3 kilometers) per year. That means an ice loss of nearly 3 feet (1 meter) of ice every hour. If you stare at the glacier for about 20 minutes you can notice it move, said University of California Irvine glacier expert Eric Rignot, who wasn't part of the study.
Even so, that pace doesn't match the predictions laid out in the worst-case laid out in the 2008 study, research that caused alarm about the effects of increasing greenhouse gas emissions that warm the earth.
"We're not seeing some kind of runaway effect," said study co-author, Ian Joughin, another University of Washington glacier scientist.
Rignot said it is unfair to compare this recent study to the more alarming 2008 one, which he said wasn't designed to be overly realistic. However, he noted that the findings of this new study still exceed computer models and projections by the Nobel Prize-winning Intergovernmental Panel on Climate Change.
NASA Chief Scientist Waleed Abdalati, an ice scientist, called the new work a "valuable study that advances our understanding of a very complex wild card of sea level rise."
Seth Borenstein be followed at http://twitter.com/borenbears