気候科学：グリーンランドの氷床の融解が270 mm以上の海面上昇につながる

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.

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.

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. 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.

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.