Seismic Impact of Large Earthquakes on Estimating Global Mean Ocean Mass Change from GRACE.

We analyze the impact of large earthquakes on the estimation of the global mean ocean mass (GMOM) change rate over the 13-year period (January 2003 to December 2015) using the Gravity Recovery and Climate Experiment (GRACE) Release-06 (RL06) monthly gravity solutions released by the Center for Space Research (CSR). We take into account the effects of the December 2004 Mw9.1 and April 2012 Mw8.6 Sumatra earthquakes, the March 2011 Mw9.0 Tohoku-Oki earthquake, and the February 2010 Mw8.8 Chile earthquake. After removing the co- and post-seismic effects of these earthquakes in the oceanic areas by least squares fitting, we estimate the GMOM rate from GRACE monthly observations. Results show that GRACE-observed GMOM rate before the seismic correction is 2.12 +/- 0.30 mm/year, while after correction the rate is 2.05 +/- 0.30 mm/year. Even though the -0.07 +/- 0.02 mm/year seismic influence on GRACE GMOM rate is small on a global scale, it is a systematic bias and should be considered for improved quantification and understanding of the global sea level change.