Greenland's ice sheet melts

From the air, Greenland's ice sheet, the second largest on Earth, appears to be perfectly still. But below the surface, the ice sheet is in constant motion, as ice built up in the interior pushes toward the coast in the form of massive glaciers. During warmer months, ice from these glaciers melts into the ocean. It's an age-old process that scientists say has speeded up in recent decades because of global warming. The fear is that melting ice from Greenland and other Arctic areas could cause sea levels to rise enough to flood low-lying cities, such as Shanghai, China, and New York City, displacing millions of people in the process. A recent report from the U.N.'s Intergovernmental Panel on Climate Change, made up of scientists from around the world, estimates the sea level rise by 2100 could be as much as 1½ feet. "That sea level rise is only based on melt from ice sheets, and does not include a new fast flow of ice we have detected in Greenland that is generating additional icebergs," said Dr. Konrad Steffen, a climate scientist with the University of Colorado, Boulder. Steffen estimates sea levels could rise three feet over the next century, a stark prediction that could wreak havoc around the world if it comes to pass. Greenland holds enough ice to cause sea levels to rise 23 feet if the entire ice sheet melted, a development few scientists expect to happen anytime soon. But global sea levels have been rising at the rate of three millimeters per year since 1993. For each of the past 17 years, Steffen has spent one month at a remote research site called Swiss Camp, located 300 miles north of the Arctic Circle in Greenland. He monitors the changing ice sheet through a network of global positioning systems and weather stations, which have recorded a dramatic rise in temperatures since the mid-1990s. "When we came here in 1990, the first two, three years were actually colder than normal. Then in 1994, 1995, it started to warm steadily and since then, we've had a temperature increase during the winter months of 4.5 degrees centigrade, 8.1 degrees Fahrenheit, which is very large, the largest temperature increase on earth," he said.