Earth’s Temporal Principal Moments of Inertia and Variable Rotation

Based on the gravity field models EGM96 and EIGEN-GL04C, the Earth’s time-dependent principal moments of inertia A, B, C are obtained, and the variable rotation of the Earth is determined. Numerical results show that A, B, and C have increasing tendencies; the tilt of the rotation axis increases 2.1×10^-8 mas/yr; the third component of the rotational angular velocity, ω₃, has a decrease of 1.0×10^-22 rad/s², which is around 23% of the present observed value. Studies show in detail that both θ and ω₃ experience complex fluctuations at various time scales due to the variations of A, B and C.