The Greenland Ice Sheet covers roughly 1.7 million square kilometers in the Arctic. If the ice sheet melts entirely, global sea level would rise about 7 meters, but scientists don’t know how quickly it could melt.
Based partly on carbon emissions, a new study using simulations identified two tipping points for the Greenland Ice Sheet: releasing 1000 gigatons of carbon into the atmosphere will cause the southern portion of the ice sheet to melt; about 2500 gigatons of carbon means permanent loss of nearly the entire ice sheet. As of now, we have released about 500 gigatons of carbon.
“The first tipping point is not far from today’s climate conditions, so we’re in danger of crossing it,” said Dennis Höning of the Potsdam Institute for Climate Impact Research who led the study. “Once we start sliding, we will fall off this cliff and cannot climb back up.”
The Greenland Ice Sheet is already melting rapidly; between 2003 and 2016, it lost about 255 gigatons (billions of tons) of ice each year. Much of the melt has been in the southern part of the ice sheet. Air and water temperature, precipitation, ocean currents and other factors all determine how quickly the ice sheet melts and where it loses ice.
Previous research determined global warming of between 1 degree to 3 degrees Celsius as the threshold beyond which the Greenland Ice Sheet will melt irreversibly.
As the ice sheet melts, its surface will be at increasingly lower elevations, exposed to warming air temperatures. Warmer air temperatures accelerate melt, making it drop and warm even further.
“We cannot continue carbon emissions at the same rate for much longer without risking crossing the tipping points,” Höning said. “Most of the ice sheet melting won’t occur in the next decade, but it won’t be too long before we will not be able to work against it anymore.”