Climate change

Greenland ice sheet melting seven times faster than in 1990s

written by Oceanographic Staff

A new study by NASA, the European Space Agency and Leeds University, has revealed that Greenland is losing ice seven times faster than in the 1990s. This rate tracks the Intergovernmental Panel on Climate Change’s (IPCC) high-end climate scenario.

As a result, 40 million more people will be exposed to coastal flooding by 2100.

The assessment found that show that Greenland has lost 3.8 trillion tonnes of ice since 1992 – enough to push global sea levels up by 10.6 millimetres. The rate of ice loss has risen from 33 billion tonnes per year in the 1990s to 254 billion tonnes per year in the last decade – a seven-fold increase within three decades.

“As a rule of thumb, for every centimetre rise in global sea level another six million people are exposed to coastal flooding around the planet,” said Professor Andrew Shepherd of the University of Leeds, who co-led the assessment. “On current trends, Greenland ice melting will cause 100 million people to be flooded each year by the end of the century, so 400 million in total due to all sea level rise. These are not unlikely events or small impacts; they are happening and will be devastating for coastal communities.”

A team of 89 polar scientists from 50 international organisations have produced the most complete picture of Greenland ice loss to date. The Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE) researchers combined 26 separate surveys to compute changes in the mass of Greenland’s ice sheet between 1992 and 2018. Data from 11 different satellite missions was used, which included measurements of the ice sheet’s changing flow, volume and gravity.

They also used regional climate models to show that half of the ice losses were due to surface melting as air temperature has risen. Increased glacier flow, triggered by rising ocean temperatures, was responsible for the other half.

Greenland ice sheet melt ice loss

“Satellite observations of polar ice are essential for monitoring and predicting how climate change could affect ice losses and sea level rise,” said Dr Erik Ivins of NASA’s Jet Propulsion Laboratory. “While computer simulation allows us to make projections from climate change scenarios, the satellite measurements provide prima facie, rather irrefutable, evidence. Our project is a great example of the importance of international collaboration to tackle problems that are global in scale.”

In 2013, the IPCC predicted that global sea levels would rise 60cm by 2100, putting 360 million people at risk of annual coastal flooding. However, the results of this study shows that Greenland’s ice losses are rising much faster than previously thought.

In 2011, annual ice losses peaked at 335 billion tonnes  – ten times the rate of the 1990s – during a period of intense surface melt. Although the rate of ice loss dropped to an average 238 billion tonnes per year since that period, this figure is still seven times higher and does not include all of 2019, which could set a new high due to widespread summer ice loss.

To read the full paper, Mass balance of the Greenland Ice Sheet from 1992 to 2018, click here.

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