Ablation rate of Perito Moreno Glacier assessed through the time integral of mass balance equation and remote sensing

Perito Moreno is one of the largest glaciers in the Southern Patagonian Ice Field. Known until recently for its unique stability against climate change, favoured by the stabilizing effect of a subglacial ridge, it is now undergoing a distinct transition. We processed images from Pléiades-SPOT satellites during 2015–2023 to create digital elevation models and compute their difference, showing an average ice thickness change of −2.7 m a−1 in the terminal area. This rapid downwasting, accelerating since 2020, is likely driven by recent atmospheric warming and severe droughts, causing the glacier front to retreat beyond its pinning point. We assessed the ablation rate at the glacier terminus by solving the mass balance equation as a function of surface elevation change, velocity field, and ice thickness along two transects, one located close to the calving front. Surface velocity was derived from 88 Sentinel-2 images at 10 m resolution, acquired from 2019 to 2024, and processed using Imgraft software. Specifically, we integrated the mass balance equation over the time required for the glacier to travel between the upstream and downstream transects. In contrast to spatial integration, this approach leverages the mean trajectory velocity, effectively smoothing out local instabilities and rendering the results robust against the high uncertainty of pointwise velocities. The ablation rate of −16.4 m w.e. a−1 during 2015–2023 is consistent with recent measurements from ablation stakes, validating the reliability of the proposed time integral framework.