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

Abstract

Glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology 1 , raising global sea-level 2 and elevating natural hazards 3 . Yet, due to the scarcity of constrained mass loss observations, glacier evolution during the satellite era is only known as a geographic and temporal patchwork 4,5 . Here we reveal the accelerated, albeit contrasted, patterns of glacier mass loss during the early twenty-first century. By leveraging largely untapped satellite archives, we chart surface elevation changes at a high spatiotemporal resolution over all of Earth's glaciers. We extensively validate our estimates against independent, high-precision measurements and present the first globally complete and consistent estimate of glacier mass change. We show that, during 2000-2019, glaciers lost 267 ± 16 Gt yr -1 , equivalent to 21 ± 3% of observed sea-level rise 6 . We identify a mass loss acceleration of 48 ± 16 Gt yr -1 per decade, explaining 6-19% of the observed acceleration of sea-level rise. Particularly, thinning rates of glaciers outside ice sheet peripheries doubled over the last two decades. Glaciers presently lose more mass, and at similar or larger accelerated rates, than the Greenland or Antarctic ice sheets taken separately [7][8][9] . Uncovering the patterns of mass change in many regions, we find contrasted glacier fluctuations that agree with decadal variability in precipitation and temperature. Those include a newly-identified North Atlantic anomaly of decelerated mass loss, a strongly accelerated loss from Northwestern American glaciers and the apparent end of the Karakoram anomaly of mass gain 10 . We anticipate our highly-resolved estimates to foster the understanding of drivers that govern the distribution of glacier change, and to extend our capabilities of predicting these changes at all scales. Predictions robustly benchmarked against observations are critically needed to design adaptive policies for the management of local water resources and cryospheric risks as well as for regional-to-global sea-level rise.About 200 million people live on land predicted to fall below the high-tide lines of rising sea levels by the end of the century 11 , while more than one billion could face water shortage and food insecurity within the next three decades 4 . Glaciers distinct from the ice sheets play a prominent role in these repercussions as the largest estimated contributor to twenty-first century sea-level rise after thermal expansion 2 , and as one of the most climate-sensitive constituents of the world's natural water towers 12,13 . Current glacier retreat temporarily mitigates water stress on populations reliant on ice reserves by increasing river runoff 1 , but this short-lived effect will eventually decline 14 . Understanding present-day and future glacier mass change is thus crucial to avoid water scarcity-induced socio-political instability 15 , to predict the alteration of coastal areas due to sea-level rise 4 , and to assess the impacts on ecosystems 16 as w...

Recent contrasting behaviour of mountain glaciers across the European High Arctic revealed by ArcticDEM data

“…Negative trends of change of small glaciers can be seen also in NZ (Ciracì et al, 2018) and FJ (Zheng et al, 2018). The recently published global atlas of glacier elevation changes at 100 m resolution by Hugonnet et al (2021) shows a comparable spatial pattern of ℎ ⁄ across the regions investigated here.…”

“…However, within the glacier boundaries used in this study, the changes calculated by Hugonnet et al (2021) for the period 2010-2019 were on average less negative by ca. 0.4 m a -1 for sites experiencing ℎ ⁄ < -1.0 m a -1 and by ca.…”

“…These facts suggest that the mass gain reported in this paper resulted from a post-1990 climate forcing, acting on a shorter timescale than the reaction time of glaciers. A recent global study of glacier elevation changes by Hugonnet et al (2021) suggests that mountain glaciers in north Spitsbergen have been 335 relatively close to balance since at least the early-2000's.…”

“…Recent progress in large-scale glacier mass balance studies, utilizing climate modelling, satellite altimetry, gravimetry and photogrammetry, fundamentally improved our knowledge on the general trends of glacier decay in the Arctic and the contribution of its ice masses to the global sea-level rise (e.g. Moholdt et al, 2012;Box et al, 2018;Noël et al, 2018;Wouters et al, 2019;Hugonnet et al, 2021).…”

Evolution of Surface Characteristics of Three Debris-Covered Glaciers in the Patagonian Andes From 1958 to 2020

“…Driven by climate change, glaciers in most high mountain ranges around the globe are receding and losing mass rapidly (Jomelli et al, 2011;Davies and Glasser, 2012;Zekollari et al, 2019;Davaze et al, 2020;Hugonnet et al, 2021). Whilst glaciers steadily thin and contribute to sea level rise through increased melting (Zemp et al, 2019), another aspect of glacier change and adjustment to drier conditions is the progressive accumulation of surface debris stemming from the surrounding valley walls and lateral moraines (Scherler et al, 2011;Kirkbride and Deline, 2013;Sasaki et al, 2016;Tielidze et al, 2020).…”