Aug. 11, 2006 — Using a space-based system to weigh the ice loss from all of Greenland, scientists say vast amounts of glacier ice is melting into the sea, boosting sea levels and raising the specter of rapid climate change in Europe.
The new measurements show that the southeastern Greenland ice sheet has been melting five times more quickly over the last two years than it did in the year and a half before that.
The study taps data from November 2005 back to April 2002, which is as far back as the measurements go with the Gravity Recovery and Climate Experiment (GRACE), a joint NASA-German Aerospace Center mission.
Earlier this year, another air- and space-based survey led by NASA's Jet Propulsion Laboratory (JPL) used images to track the physical changes throughout Greenland. That study revealed an abrupt northward glacial retreat, spilling vast amounts of ice into the sea.
The trend in disintegrating coastal glaciers was clocked at 300 miles (480 kilometers) over the last five years. That comes to about 54 cubic miles (225 cubic kilometers) of icy water lost each year and dumped into the North Atlantic.
"We came to roughly the same conclusion," said Jianli Chen of the University of Texas in Austin. Chen was the lead author of a new report on the GRACE survey in the current issue of Science Express.
The net rise in global sea level from added glacier water comes to 0.56 millimeters per year, which is about one-fiftieth of an inch, Chen reported. Put another way, if the melting in Greenland continued at the same rate until the year 2056, it would add another inch to the already rising sea level.
For comparison, sea level rise in the 20th century was between 4 and 8 inches, without any additional water from Greenland, according to recent studies.
A Colder Europe?
Gordon Hamilton, a Greenland ice expert at the University of Maine who commented on the JPL study earlier this year, said then that all this could mean trouble not just in terms of sea level rise worldwide. There are worries that all the ice entering the North Atlantic could slow down the global heat conveyor belt known as the thermohaline circulation.
In the North Atlantic, that conveyor belt plunges down, taking with it dense, salty, cool surface waters that have ridden the Gulf Stream north. There, the current turns south and re-circulates the dense water to warmer seas.
But more buoyant, fresh, glacial water in the North Atlantic could sit atop the surface waters, blocking the sinking and halting the entire conveyor belt. If that happened, the weather would turn much colder in Europe and warmer in the tropics. It's something that could be seen in the next decade, said Hamilton.
