Accelerated global glacier mass loss in the early twenty-first century

Abstract:

Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, impacting regional hydrology, raising global sea-level and altering natural hazards. Yet, due to the scarcity of homogeneous mass loss observations, their recent evolution is only partially known as a geographic and temporal patchwork. Here, by leveraging untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth’s glaciers. We extensively validate our novel approaches against independent, high-precision measurements and present the first globally complete and consistent estimate of 21st century glacier mass change. We show that, during 2000-2019, glacier mass loss totalled 266 ± 16 gigatons per year, equivalent to 24 ± 5% of observed sea-level rise. In two decades, mass loss increased by 97 ± 20 gigatons per year and, excluding ice sheet peripheral glaciers, ice thinning rates doubled. Collectively, glaciers presently lose more mass, and at more accelerated rates, than the Greenland or Antarctic ice sheets. Uncovering the patterns of glacier mass change, we find regional-scale fluctuations that agree with decadal variability in precipitation and temperature, including a North Atlantic anomaly of decelerated mass loss, contrasted with a strong accelerated loss from Northwestern American glaciers and the apparent end of the Karakoram anomaly of mass gain. Beyond these large-scale findings, we anticipate our resolved estimates to lead towards increased understanding of the drivers of glacier mass change. This observational baseline is not only required to improve physically-based modelling but also to constrain the calibration of future projections at all scales and extend their predictive reach to drive adaptive policies as well for local cryospheric risks and freshwater availability as for global sea-level rise.