Correction of GRACE measurements of the Earth's moment of inertia (MOI)

The widely used 15-year Gravity Recovery and Climate Experiment (GRACE) data sets do not conserve global total mass. They have a spurious decreasing trend of similar to 280 Gt/year. Various regions contribute differently to the global total mass loss error, with the Greenland Ice Sheet (GrIS) generating similar to 10% of the error alone. Atmospheric parameters from reanalysis datasets drive a well-tested ice model to generate mass variation time series over the GrIS for 2002-2015. Because shorter timescale spikes of similar to 10-30 Gt in GRACE measurements are physically based, only the overall trend of similar to 30 Gt/year requires correcting. A more accurate mass loss rate estimate for 2002-2015 is similar to 120 Gt/year, considerably below previous estimates. With the water redistribution to lower latitudes and other effects from a warming climate, the nontidal Earth moment of inertia (MOI) also increases. After rectification, the GRACE measured mass redistribution shows a steady, statistically robust (passed a two-tailed t-test at p = 0.04 for dof = 15) rate of MOI increase reaching similar to 10.1 x 10(27) kg m(2)/year, equivalent to a 10.91 mu s/year increase in the length of a day, during 2002-2017.

Automated summary

The 15-year GRACE data sets show a spurious decreasing trend in global total mass, with Greenland Ice Sheet contributing significantly to the error. By analyzing the mass variation over the GrIS and rectifying the measurements, researchers found a more accurate global mass loss rate estimate for 2002-2015. The study also indicates an increase in the non-tidal Earth moment of inertia due to water redistribution and other effects from a warming climate.