NASA study halves estimate of Earth’s seasonal centre-of-mass movement
A new satellite-tracking technique estimates that seasonal shifts caused by water, ice and air move Earth’s centre of mass by several millimetres each year.
NASA-led researchers have developed a satellite-tracking technique to refine estimates of how Earth’s centre of mass shifts relative to its geometric centre as water, ice and air move around the planet.
The study, published in Geophysical Journal International, estimates the annual movement at several millimetres — about half the size reported in previous estimates. The revised figure is an updated measurement, not evidence that the planet’s physical movement has decreased.
Earth’s centre of mass is a reference point for satellite navigation, mapping and elevation measurements. Seasonal snow, rain, monsoon water, ocean changes and dense winter air all contribute to the shift.
The technique combines GPS and low-Earth-orbit satellite data with orbital measurements. It also accounts for deformation of Earth’s crust caused by the weight of water and ice, helping address limitations in the uneven global distribution of ground stations used for satellite laser ranging.
The researchers’ modelled mass calculations are consistent with observations from NASA’s GRACE-FO mission, which has mapped monthly changes in Earth’s gravitational pull since its launch in 2018. However, the exact size of the seasonal movement remains uncertain: international estimates published in 2017 and 2023 differed by 7 millimetres.
