Frontal ablation and mass loss of the Patagonian icefields

The complex dynamics of calving glaciers is a major uncertainty in projecting global glacial mass loss. We present frontal ablation and ice mass change for the 38 major calving glaciers in the Patagonian icefields based on remote-sensing observations of ice-front positions, surface speeds and elevation changes. The frontal ablation from 2000 to 2019 was −24.1 ± 1.7 Gt a−1, which represents 34 ± 6% of the total ablation of the icefields. The fraction of frontal ablation was close to half in the southern icefield and about one fifth in the northern icefield. The rate of the mass loss from the icefields during the period of study was 15.2 ± 3.5 Gt a−1, which is generally explained by surface mass balance but was accelerated as a result of increasing frontal ablation. The frontal ablation and mass change values suggest surface mass balance to be −1.5 ± 0.9 Gt a−1 for the northern icefield and +11.5 ± 2.7 Gt a−1 for the southern icefield during this period. Our study demonstrates that a strong increase in frontal ablation at several glaciers drives the mass loss in the southern icefield, whereas increasingly negative surface mass balance drives the mass loss in the northern icefield.