Unprecedented mass loss expected for the Greenland Ice Sheet

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Nature

(With some minor editing by PinP.)

The edge of the Greenland Ice Sheet.  Credit: Jason Briner

Mass loss from the Greenland Ice Sheet is predicted to be higher in this century than any time in the past 12,000 years. The simulations, published in Nature, are based on high-carbon-emission scenarios and consider the southwestern region of Greenland. The findings add to a body of evidence that suggests that reducing carbon emissions is needed to decrease the contribution of the Greenland Ice Sheet to sea-level rise.

As the Arctic warms, the Greenland Ice Sheet has been losing mass and contributing to sea-level rise. That loss rate has increased dramatically since the 1990s. But are those rates and ones projected for the future unexpected? Or, are they just related to "natural variability?" To answer that question, Jason Briner and colleagues produced high-resolution simulations based on geological observations covering southwestern Greenland for the past 12,000 years that extend continuously into the future up to 2100.

The Greenland Ice Sheet.  Credit: Jason Briner

The simulations suggest that mass loss from the Greenland Ice Sheet in the twenty-first century will exceed the maximum mass-loss rates from the past 12,000 years. They find the largest losses in the past (between 10,000 and 7,000 years ago) were at rates of around 6,000 billion tonnes per century. That's similar to the estimated rates of the first two decades of this century. 

However, future losses are expected to exceed those maximum rates. Projected mass losses for the rest of this century are in the range of 8,800 to 35,900 billion tonnes. Those are based on the lowest and highest greenhouse gas emissions scenarios, respectively - that is, the amount of ice losses this century could reverse 4,000 years of cumulative ice growth and exceed previous mass-loss rates by about fourfold. The authors conclude that unprecedented rates of mass loss will occur unless a low-carbon-emission scenario is followed.

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