An annual mass balance estimate for each of the world’s glaciers based on observations

The geodetic method has become a popular tool to measure glacier elevation changes over large glacierized regions with high accuracy for multi-annual to decadal time periods. In contrast, the glaciological method provides annually to seasonally resolved information on glacier evolution, but only for a small sample of the world’s glaciers (less than 1%). Various methods have been proposed to bridge the gap on spatio-temporal coverage of glacier change observations and to provide annually-resolved glacier mass balances using the geodetic sample as calibration. Thanks to a new global and near-complete (96% of the world glaciers) dataset of geodetic mass balance observations, this goal has become feasible at the global scale. Inspired by previous methodological frameworks, we developed a new approach to combine the glacier distribution from the globally-complete Randolph Glacier Inventory with the mass balance and elevation change observations from the Fluctuation of Glaciers database of the World Glacier Monitoring Service (WGMS). Our results provide a global assessment of annual glacier mass changes and related uncertainties for every individual glacier during the 2000–2020 period. The glacier-specific time series can then be integrated into an annually-resolved global gridded glacier change product at any user-requested spatial resolution, useful for comparison with gravity-based products, calibration or validation of glacier mass balance models operating at a global scale and to improve calculations of the glacier contribution to regional hydrology and global sea-level rise.