Glacier melt contributing more to sea-level rise than loss of Greenland and Antarctic ice sheets, say experts

The melting of the world’s glaciers has nearly doubled in speed over the past 20 years and contributes more to sea-level rise than either the Greenland or Antarctic ice sheets, according to the most comprehensive global study of ice rivers ever undertaken. Scientists say human-driven global heating is behind the accelerating loss of high-altitude and high-latitude glaciers, which will affect coastal regions across the planet and create boom-and-bust flows of meltwater for the hundreds of millions of people who live downstream of these “natural water towers”.

Between 2000 and 2019, glaciers lost 267 gigatonnes (Gt) of ice per year, equivalent to 21% of sea-level rise, reveals a paper published in Nature. The authors said the mass loss was equivalent to submerging the surface of England under 2 metres of water every year. This was 47% higher than the contribution of the melting ice sheet in Greenland and more than twice that from the ice sheet in Antarctica. As a cause of sea-level rise, glacier loss was second only to thermal expansion, which is prompted by higher ocean temperatures. The authors found the pace of glacier thinning outside of Greenland and Antarctica picking up from about a third of a metre per year in 2000 to two-thirds in 2019. This is equivalent to an acceleration of 62Gt per year each decade.

The study uses historical Nasa satellite data and new statistical methods to construct three-dimensional topographies going back 20 years and covering 99.9% of the world’s glaciers. The result is the most accurate and comprehensive assessment of the world’s 217,175 glaciers to date. Scientists said the precision of the data allowed them to be more certain than before that glacier loss is enormous and accelerating. Previous estimates of mass loss were about 20% more negative, but those had an even greater margin of error because they were either extrapolated from ground measurements at a few hundred reference glaciers and a limited coverage of satellite imagery, or based on the study of gravimetric signals which have a coarse resolution.

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