GRACE-derived land-hydrological mass changes and their impact on relative sea-level variations

Abstract

The GRACE (Gravity Recovery And Climate Experiment) mission allows inference of mass variations on, above and beneath the Earth’s surface from gravitational signatures in space. We present a robust and straightforward procedure to derive mass changes from time-variable gravity field estimates. We outline our solution to the leakage problem and shed light on linear versus accelerated secular-change modeling. Based on a six-year gravity field time-series from March 2003 to February 2009, we provide detailed analysis of two selected areas, Greenland and the Orinoco Basin. As a result, annual Greenland mass loss accelerated by +21.3±3 Gt/yr2 during the six-year period. Furthermore, we show the impact of recent ice melting on global relative sea level. In terms of uniform change, the contributions of Greenland and Antarctica are +0.56±0.01 mm/yr and +0.50±0.07 mm/yr, respectively. However, we prove that simplistic uniform modeling of sea-level variations is insufficient as it disregards the gravitational feedback effect caused by mass redistribution.