Monday, August 29, 2022

Climate science: Greenland ice sheet to contribute over 270mm to sea-level rise

Nature Climate Change

The overall loss of ice from the Greenland ice sheet — alongside increasing precipitation, ice flow discharge and meltwater runoff — will lead to at least 274 mm in sea-level rise, regardless of future climate warming projections, according to a study published in Nature Climate Change.

The glaciologist team setting up an automatic weather station on the snowy surface above the snow line during the melt season. Credit: The Geological Survey of Denmark and Greenland, GEUS

Greenland’s ice budget deficit emerged after the 1980s when it began losing more ice, due to surface melt runoff and ice flow discharge, than it gained in the accumulation of precipitation. However, despite its importance to future sea-level rise, the ability to accurately predict Greenland’s response to climate change is hindered by the imprecise measurements of land, atmosphere and ocean boundaries in current models.

Professor Jason Box taking ice samples standing on exposed ice below the snow line of the Greenland Ice Sheet in West Greenland during the melt season. Credit: The Geological Survey of Denmark and Greenland, GEUS

Using climate data from 2000 to 2019, Jason Box and colleagues calculated the committed changes in ice-sheet volume and area incurred by Greenland’s ice imbalance. The authors reveal that surface ablation through meltwater runoff was the primary driver of the variability of the Greenland ice sheet mass budget from year to year. 

In the recent (2000–2019) climate, the Greenland ice has built up a disequilibrium which will inevitably correct itself by reducing total mass by at least 3.3 percent in order to regain equilibrium at a new average snow line in a higher alteration. Credit: The Geological Survey of Denmark and Greenland, GEUS

Losses from the ice sheet will already lead to a rise of at least 274 mm in sea level from 5,900 km2 of ice retreat — equivalent to a volume loss of 3.3% — regardless of future climate scenarios.
The minimum global sea level rise and likely global sea level rise resulting from the committed mass loss from the Greenland Ice Sheet. Credit: The Geological Survey of Denmark and Greenland, GEUS

If the high melt year of 2012 is considered to be indicative of normal in the future, then ice loss and consequent sea-level rises could be committed to 782 mm, which the authors conclude should act as a warning for Greenland’s future, as temperatures rise in the twenty-first century.

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