Secular polar motion observed by GRACE.

A long-term drift in polar motion (PM) has been observed for more than a century, and Glacial Isostatic Adjustment (GIA) has been understood as an important cause. However, observed PM includes contributions from other sources, including contemporary climate change and perhaps others associated with Earth's interior dynamics. It has been difficult to separate these effects, because there is considerable scatter among GIA models concerning predicted PM rates.

Global sea level change signatures observed by GRACE satellite gravimetry.

Ice mass loss on land results in sea level rise, but its rate varies regionally due to gravitational self-attraction effects. Observing regional sea level rates by ocean mass change using the Gravity Recovery and Climate Experiment (GRACE) gravity solutions is difficult due to GRACE's spatial resolution (~a few hundred km) and other limitations. Here we estimate regional sea level mass change using GRACE data (without contributions from temperature and salinity variations) by addressing these limitations: restoring spatially spread and attenuated signals in post-processed GRACE data; constraining ocean mass distribution to conform to the changing geoid; and judging specific corrections applied to GRACE data including a new geocenter estimate.