Earth’s center of mass is not a fixed point; it constantly shifts by several millimeters as water, ice, and air redistribute across the planet. A research team led by NASA’s Jet Propulsion Laboratory (JPL) has developed a new technique to measure these seasonal oscillations with greater accuracy, addressing discrepancies in previous international estimates.
The study, published in Geophysical Journal International, utilizes a combination of satellite laser ranging, GPS tracking, and orbital data from low Earth orbit satellites. By accounting for how the weight of water and ice deforms the Earth's crust—which in turn moves ground-based tracking stations—the researchers have reduced uncertainty in their calculations. According to lead author and JPL geoscientist Donald Argus, the team now estimates the annual movement of the center of mass to be roughly half of what was previously believed, suggesting that the mass of water and air shifting between hemispheres is smaller than earlier models indicated.
The research identifies three primary drivers for these shifts: the atmosphere, the oceans, and continental water, which includes groundwater, snow, and land ice. For example, the study notes that snow accumulation in North America and Eurasia peaks in March, pulling the center of mass approximately 3 millimeters toward the North Pole. Similarly, the massive influx of rainwater in the Amazon basin during April shifts the center of mass toward South America by 2.2 millimeters.
These findings align with data from the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission, a joint effort between NASA and the German Research Centre for Geosciences. Coauthor Felix Landerer emphasized that while these movements are minute, they are critical for maintaining the precision of modern navigation and mapping systems. Understanding these mechanisms is essential for applications ranging from global shipping logistics to precision agriculture.
Source: NASA
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