NASA Develops New Technique to Track Earth's Shifting Center of Mass

• NASA scientists have developed an ultra-precise satellite tracking technique to measure how Earth's center of mass oscillates seasonally.
• The study reveals that the displacement caused by the movement of water, ice, and air is roughly half of previous estimates.
• Improved positioning measurements are vital for global logistics, shipping, and precision agriculture.

Drivers of Mass Displacement

• Earth's center of mass shifts due to surface weight fluctuations, oscillating by up to several millimeters relative to its geometric center.
• The researchers categorized the causes of these seasonal shifts into three main groups:
  • Continental water: Accumulation of snow in North America/Eurasia (March, 3mm toward the North Pole), rainfall in the Amazon basin (April, 2.2mm toward South America), and monsoon cycles in Southeast Asia (November).
  • Oceans: Swelling levels between August and October shift the mass center toward the South Pacific, with other seas playing smaller roles.
  • Atmosphere: Seasonal density changes in air mass shift the center over regions including Arabia, Asia, and South America.

Technical Advancements

• The new approach integrates GPS tracking with orbital data from multiple low Earth orbit satellites to provide more diverse targets than previous laser-ranging methods.
• The model accounts for crustal deformation caused by the weight of water and ice, improving accuracy by correcting for the movement of ground stations.
• These findings align with data from the GRACE-FO mission, which maps monthly gravitational fluctuations, and will be further expanded by the upcoming GRACE-C mission in late 2028.