Long‐period variations in gravity field caused by mantle anelasticity

Abstract

A numerical perturbation approach is used to assess the effect of mantle anelasticity on the Earth's zonal response coefficient κ, the zonal geopotential coefficient J 2 , and the orbital node of geodetic satellites. The theoretical predictions are used to compare solutions of elastic ocean tide models and tides observed by geodetic satellites for M f , M m , S sa , and S a . The discrepancies between the satellite observed tides and the solution from Schwiderski and recent altimetric ocean tide models can be partly explained by the predicted effect of mantle anelasticity at M f and M m frequencies. Approximately 80% of the observed semiannual variation in δ J 2 by geodetic satellites can be attributed to the tidal deformation from anelasticity and from the classical equilibrium ocean. The predicted κ for the 18.6‐year tide was computed for an Earth with an anelastic mantle and a nonequilibrium ocean. The range of the lower and upper bounds of κ for the 18.6‐year tide is from 0.345 to 0.377 in amplitude, and from −6° to 3° in phase, with preferred amplitude of 0.365 and phase of −0°.8.