Low-Degree Gravity Change and Surface Mass Variations

Chen, Jianli; Wilson, Clark
Center for Space Research, University of Texas at Austin, Austin, TX, chen@csr.utexas.edu

The Earth gravitational variation is caused by mass redistribution within the Earth system, including the atmosphere, ocean, land, cryosphere, and solid Earth. Gravitational change can be quantified by geodetic measurements and numerical models. In this study, we examine time series of low-degree gravitational variations, ΔC21, ΔS21, and ΔC20 estimated from four different methods, including satellite gravimetry from the Gravity Recovery and Climate Experiment (GRACE), Earth Orientation Parameters (length of day and polar motion), advanced climate models (including atmospheric, oceanic, and hydrologic models), and satellite laser ranging. We compare these independent estimates at different time scales, and discuss major uncertainties for the various techniques. These independent estimates of ΔC21, ΔS21, and ΔC20 are important for validating geodetic techniques and for improving understanding of large-scale mass redistribution within the Earth system. We will examine the low frequency variability of these low degree gravitational changes and its possible connection to large-scale climate change events within the Earth system, including ice loss from polar ice sheets and mountain glaciers, terrestrial water storage change, and sea level change.