Science 326, 984–986 (2009).

Credit: Courtesy of Steve Morgan

Greenland, home to one-tenth of the world's land ice, is rapidly losing mass, pushing up global sea levels. Approximations of how fast this is happening vary widely, but a study now offers one estimate verified using two independent methods.

An international team led by Michiel van den Broeke at Utrecht University in the Netherlands gauged the rate at which the Greenland ice sheet is shrinking based firstly on observations of ice movement, melting and snowfall. They then compared these results with remote gravity measurements made by a pair of US–German satellites known as GRACE (the Gravity Recovery and Climate Experiment). They found that, on average, the ice sheet lost a total of about 1500 gigatons of mass between 2000 and 2008, equivalent to about 0.46 millimetres of global sea level rise per year. The loss of mass during this time was split equally between surface processes, such as melting, and the physical discharge of large chunks of ice into the ocean.

From 2006 to 2008, the rate of ice loss accelerated, mostly due to high rates of summer surface melting, reaching 273 gigatons of mass per year, or 0.75 millimetres of annual sea level rise.