Snow, monsoons and oceans shift Earth's center of mass each year, satellite tracking shows

NASA scientists have developed a new technique using ultraprecise satellite tracking to estimate the displacement of Earth's center of mass relative to its geometric center, with accuracy within fractions of an inch. The study shows that seasonal changes redistribute water around Earth, shifting the planet's center of mass back and forth by as much as several millimeters. The technique, led by NASA's Jet Propulsion Laboratory, tracks the oscillations and calculates the movement of Earth's mass center each year. The findings suggest that the mass of Earth's water and air moving between the hemispheres is smaller than previously thought.

The study attributes the movement to three categories: oceans, atmosphere, and continental water. It found that snow accumulation in North America and Eurasia shifts Earth's center of mass about 3 millimeters toward the North Pole, while rainwater in the Amazon River basin shifts it 2.2 millimeters toward South America. Monsoon water in Southeast Asia adds slightly to the annual oscillation. The researchers used a model to estimate how atmospheric changes affect Earth's center of mass, noting that cold, dense winter air tips the scales over specific regions around December 21 and June 21.

The study's findings are consistent with observations from the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission. The technique improves accuracy by incorporating GPS tracking and orbital data from low Earth orbit satellites, and considers how water and ice deform Earth's crust. The research highlights the importance of understanding Earth's center of mass for satellite navigation and elevation measurements, and suggests that the movement of Earth's mass is smaller than previously believed.

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