NASA researchers estimate Earth's center of mass shift at about half the previous estimate — ScienceDaily
Researchers at NASA’s Jet Propulsion Laboratory in Southern California, United States, have developed a method for more accurately measuring seasonal shifts in Earth’s center of mass. The analysis showed that the planet’s annual center-of-mass movement is approximately half as large as was believed eight years ago, ScienceDaily reports.
The center of mass does not always coincide with Earth’s geometric center because water, ice, and air are redistributed between regions and hemispheres throughout the year. As a result, the center of mass shifts by several millimeters relative to the geometric center. Such a reference point is important for satellite navigation and surface-elevation measurements.
Laser measurements and GPS
The new approach combines laser tracking of the LAGEOS 1 and LAGEOS 2 satellites, GPS data, and orbital information on several satellites in low Earth orbit. LAGEOS 1 and LAGEOS 2 were launched in 1976 and 1992; ground stations in more than 20 countries direct laser beams at them and measure the returning signals.
The method also accounts for deformation of Earth’s crust under the influence of changing water and ice mass, as ground stations shift slightly along with the surface. Two international estimates released in 2017 and 2023 differed by 7 millimeters—nearly the magnitude of the movement scientists are trying to detect.
More current news is available on the UA.News Telegram channel Telegram.
Impact of snow, water, and the atmosphere
The researchers linked seasonal shifts to the oceans, atmosphere, and water on land—including ice, snow, rivers, lakes, soil moisture, and groundwater. The greatest accumulation of snow in North America and Eurasia in March shifts the center of mass by approximately 3 millimeters toward the North Pole.
In April, the Amazon basin contains about 2,400 gigatons of seasonal rainwater, shifting the center of mass by 2.2 millimeters toward South America. Monsoon water in Southeast Asia reaches its peak in November at about 600 gigatons. From August to October, meltwater and precipitation increase the mass of the oceans and shift the center of mass toward the southern Pacific Ocean.
The mass estimates are consistent with observations from the GRACE-FO mission, whose two satellites track monthly changes in Earth’s gravitational field. The next GRACE-C mission is expected to continue this observation record; its launch is scheduled for late 2028.
