Impact of seasonal water shifts on Earth's centre of mass
Seasonal changes in the global water cycle cause water to be redistributed over the planet's surface. This redistribution is large enough to shift Earth's centre of mass back and forth by a few fractions of an inch relative to the geometric centre. The motion follows the annual cycle and results from variations in snow, ice and water storage on continents and in oceans.
A NASA research team continuously tracks these oscillations because the precise location of the mass centre serves as a fundamental reference for accurate satellite orbits and elevation measurements. Even small errors can propagate into orbit determination mistakes and biases in altimetry data.
Scientists combine satellite gravimetry, ground‑based observations and geophysical modelling to quantify the temporal variations. The findings help improve reference frames such as the International Terrestrial Reference Frame and boost the precision of navigation and Earth‑observation missions.