Decadal and quadratic variations of Earth's oblateness and polar ice mass balance from 1979 to 2010

Abstract

Gravity variations associated with Earth's oblateness (J2) have been observed by satellite laser ranging (SLR) since 1976. The J2 time-series has been used to measure and help understand many geophysical processes within the Earth system ranging from the mantle to the atmosphere. While post glacial rebound and the Earth climate system are believed to be the primary driving forces of long-termand seasonal J2 variations, the physical cause of decadal and longer timescale J2 variations has remained uncertain, although recent evidence indicates that polar ice mass changes are important. In this study, we estimate a variety of climate contributions to J2 over the period 1979？2010, and find that ice mass variations in Greenland and Antarctica are the dominant cause of observed decadal and longer J2 variations. Residual variations at periods near 10？11 years may reflect limitations of numerical climate models in estimating mass change variability at long periods, but are also suggestive of potential contribution related to variable solar activity.