Glacier slowdown and rapid ice loss in the Tinguiririca and Cachapoal Basin, Central Andes of Chile

The central region of Chile is home to nearly 10 million people, 60% of the country's population. This area's water supply is reliant on glacial meltwater from the Andes, especially during the dry summer months. However, the current ice volumes and rates of ice loss remain uncertain in many glacierized Andean basins. Our study investigated the dynamics of glaciers located in the high-altitude Tinguiririca and Cachapoal Basin over the period 2016-2022, by measuring their surface velocity and inverting for changes in ice thickness. We measured the glacier surface velocities using the Glacier Image Velocimetry toolbox on Sentinel 2 images, merging over 6000 individual velocity measurements into median annual velocity maps. We then used ice velocities as input for ice-thickness inversions to calculate ice-thickness maps and ice volumes using an ensemble of four different methods. We detect a decrease in surface velocity from 2016 to 2022 on the Universidad, Cortaderal, Norte Cipreses glaciers and southern part of the Palomo glacier, while the Cipreses glacier and the northern part of the Palomo glacier showed a decrease in velocity between 2016 and 2021 and then an acceleration in 2022. Ice thickness data shows an ice volume loss of between 0.34 +/- 0.22 and 0.43 +/- 0.18 km(3)/yr depending on the method used, equivalent to similar to 25% of the total ice volume lost from 2016 to 2022. The current rates of ice volume loss are unsustainable beyond the next two decades, reducing or entirely removing the glacial contribution to streamflow and increasing pressure on local water resources.