Solid pole tide in global GPS and superconducting gravimeter observations: Signal retrieval and inference for mantle anelasticity

- Optimal stacking method used to estimate degree-2 order-1 Love numbers from pole tide.
- We obtain well-constrained estimates for h21, l21, δ21 and k21 at CW frequency.
- We estimate the mantle anelasticity and associated material-dependent exponent α.

The mantle anelasticity plays an important role in Earth's interior dynamics. Here we seek to determine the lower-mantle anelasticity through the solution of the complex Love numbers at the Chandler wobble period. The Love numbers h21, l21, δ21 and k21 are obtained in the frequency domain by dividing off the observed polar motion, or more specifically the pole tide potential, from the observed GPS 3-D displacement field and SG gravity variation. The latter signals are obtained through the array processing method of OSE (optimal sequence estimation) that results in greatly enhanced signals to be extracted from global array data. The resultant Love number estimates h21=0.6248(±5e−4)−0.013(±5e−3)i, l21=0.0904(±8e−4)−0.0008(±2e−3)i, δ21=1.156(±2e−3)−0.003(±1e−3)i and k21=0.3125(±2e−3)−0.0069(±3e−3)i are thus well-constrained in comparison to past estimates that vary considerably. They further lead to estimates of the corresponding mantle anelastic parameters fr and fi, which in turn determines, under the single-absorption band assumption, the dispersion exponent of α=0.21±0.02 with respect to the reference frequency of 5 mHz. We believe our estimate is robust and hence can better constrain the mantle anelasticity and attenuation models of the Earth interior.