Models of isostatic and dynamic topography, geoid anomalies, and their uncertainties

Knowledge of the dynamic topography at Earth's surface caused by sublithosp heric density contrasts would provide crucial constraints on models of mant le dynamics. We calculate global models of this dynamic topography by subtr acting from the observed topography estimates of the topography caused by a ssumed isostatically compensated density variations in the crust, the ocean ic lithosphere, and the continental tectosphere. We also calculate the isos tatic geoid anomaly that would result from these compensated near-surface d ensity anomalies. Because there is controversy about the thermal structure of old oceanic lithosphere, we investigate two models of the cooling of the oceanic lithosphere (half-space and plate) and calculate the effect of eac h on the inferred dynamic topography. Peak amplitudes of dynamic topography from sublithospheric sources expanded to spherical harmonic degree 6 are a pproximately +/-1 km. We estimate the uncertainties in the calculated dynam ic topography and geoid by combining the errors in the data and systematic errors. To obtain the spectral coefficients of the fields, we use weighted least squares inversions. The calculated dynamic topography arising fi om s ublithospheric sources, residual geoid, and errors associated with these fi elds can be used in studies of mantle dynamics.