Iceland hotspot track in southeast Greenland causes huge present-dayvertical viscoelastic motion of the bedrock

The process of Glacial Isostatic Adjustment (GIA) represents the ongoing response of the solid Earth to past icemass loss that occurred following the Last Glacial Maximum (LGM, ca. 21 ka B.P.). The magnitude of the GIAuplift depends on the temporal history of the ice load and is highly sensitive to variations in upper mantle viscosity.Greenland GIA is thought to be well contained and due to relative high viscosity, influence of more recent changese.g. since the Little Ice Age have minor present-day effect (u003c2 mm/yr). Here we use data from the Greenland GlobalPositioning System (GPS) network to measure GIA. We identify an unexpected GIA anomaly of ca. 12 mm/yr insoutheast Greenland, which we interpret as linked to a zone of warmer upper mantle caused by the Iceland hotspottrack that would reduce the viscosity and produce greater viscoelastic uplift due to recent ice mass changes. Wereconsider the evolution of the Greenland ice sheet since LGM and estimate a total ice mass loss equivalent to sealevel rise of 4.9 m since LGM. Our observations suggest southeast and northwest Greenland, subject to present-daymajor ice loss, also contributed by significantly more mass loss on millennia scale than previously estimated.