GPS Measurement of Accelerating Uplift in Northern Hemisphere

Vertical GPS observations are typically less accurate and hence more difficult to interpret than horizontal observations. Recent progress in GPS technology and processing strategies as well as long GPS time series are now available, allowing precise estimates of changes in vertical positions and velocities. We use models to separate long term changes (accelerating uplift, velocity changes, and plate motion) from short term variations in GPS time series. Our results show that GPS stations located on the rocky margins of Greenland, Iceland and Svalbard show a pattern of accelerating uplift over the last decade. Other stations in Canada as well as in Scandinavia do not show such an accelerating uplift pattern. We suggest that this is due to recent accelerated melting of multi-year land ice throughout the North Atlantic region, and consequent accelerating upward motion of the crust to maintain isostatic (gravitational) equilibrium. We use the same method to examine other GPS stations in northern hemisphere and Antarctica. Preliminary results suggest that Antarctica stations do not show significant accelerating uplift.