Dynamic response of three lake-terminating glaciers to an abrupt drainage of Lago Greve, the Southern Patagonia Icefield

Abrupt drainage of a proglacial lake provides an opportunity to investigate the response of a lake-terminating glacier to a water level change. In April–July 2020, Lago Greve, a large proglacial lake in the Southern Patagonia Icefield, abruptly drained and the lake level dropped by ~18 m. Using satellite remote sensing data from 2017–2021, we quantified changes in ice velocity, ice-front position, surface elevation, and frontal ablation of three lake-terminating glaciers (Glaciar Pío XI, Greve, and Lautaro), flowing into Lago Greve. The glaciers exhibited contrasting dynamic responses to the same magnitude of water level variation. Glaciar Pío XI decelerated to <10% of the pre-event speed during the drainage, most likely because of decrease in subglacial water pressure. Glaciar Greve showed speed-up, ice-front advance and surface lowering, which were triggered by the reduction in the hydrostatic water pressure acting on the glacier front. Glaciar Lautaro showed no clear response attributable to the drainage. These contrasting behaviors demonstrated the importance of individual settings, e.g., subglacial hydrology, bed geometry, and frontal ablation, to predict the dynamics of calving glaciers, including both lake- and marine-terminating glaciers.