We have detected a global mode of Earth deformation that is predicted by theory. Precise positioning of Global Positioning System sites distributed worldwide reveals that during February to March, the Northern Hemisphere compresses (and the Southern Hemisphere expands), such that sites near the North Pole move downward by 3.0 millimeters, and sites near the equator are pulled northward by 1.5 millimeters. The opposite pattern of deformation occurs during August to September. We identify this pattern as the degree-one spherical harmonic response of an elastic Earth to increased winter loading of soil moisture, snow cover, and atmosphere. Data inversion shows the load moment's trajectory as a great circle traversing the continents, peaking at 6.9 × 10 ²² kilogram meters near the North Pole in winter, indicating interhemispheric mass exchange of 1.0 × 10 ¹⁶ ± 0.2 × 10 ¹⁶ kilograms.

Since 1995 several ice shelves in the Northern Antarctic Peninsula have collapsed and triggered ice-mass unloading, invoking a solid Earth response that has been recorded at continuous GPS (cGPS) stations. A previous attempt to model the observation of rapid uplift following the 2002 breakup of Larsen B Ice Shelf was limited by incomplete knowledge of the pattern of ice unloading and possibly the assumption of an elastic-only mechanism. We make use of a new high resolution dataset of ice elevation change that captures ice-mass loss north of 66°S to first show that non-linear uplift of the Palmer cGPS station since 2002 cannot be explained by elastic deformation alone. We apply a viscoelastic model with linear Maxwell rheology to predict uplift since 1995 and test the fit to the Palmer cGPS time series, finding a well constrained upper mantle viscosity but less sensitivity to lithospheric thickness. We further constrain the best fitting Earth model by including six cGPS stations deployed after 2009 (the LARISSA network), with vertical velocities in the range 1.7 to 14.9 mm/yr. This results in a best fitting Earth model with lithospheric thickness of 100-140 km and upper mantle viscosity of View the MathML source6×1017-2×1018 Pas - much lower than previously suggested for this region. Combining the LARISSA time series with the Palmer cGPS time series offers a rare opportunity to study the time-evolution of the low-viscosity solid Earth response to a well-captured ice unloading event

Summary. A 66-station GPS network spanning central Greece, first observed in 1989, has been occupied fully on three occasions: June 1989, October 1991 and May

We present spatiotemporal mass balance trends for the Antarctic Ice Sheet from a statistical inversion of satellite altimetry, gravimetry, and elastic‐corrected GPS data for the period 2003–2013. Our method simultaneously determines annual trends in ice dynamics, surface mass balance anomalies, and a time‐invariant solution for glacio‐isostatic adjustment while remaining largely independent of forward models. We establish that over the period 2003–2013, Antarctica has been losing mass at a rate of −84 ± 22 Gt yr⁻¹, with a sustained negative mean trend of dynamic imbalance of −111 ± 13 Gt yr⁻¹. West Antarctica is the largest contributor with −112 ± 10 Gt yr⁻¹, mainly triggered by high thinning rates of glaciers draining into the Amundsen Sea Embayment. The Antarctic Peninsula has experienced a dramatic increase in mass loss in the last decade, with a mean rate of −28 ± 7 Gt yr⁻¹ and significantly higher values for the most recent years following the destabilization of the Southern Antarctic Peninsula around 2010. The total mass loss is partly compensated by a significant mass gain of 56 ± 18 Gt yr⁻¹ in East Antarctica due to a positive trend of surface mass balance anomalies.