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The Impact of Surface Geophysical Fluids on the Earth’s Gravity, Rotation, and Shape


IPGP - Campus Jussieu


Séminaires généraux de l’IPGP

Salle Bleue

Richard GROSS

JPL, CalTech, USA

Abstract: The rearrangement of mass within the surficial fluid layers of the Earth, including the atmosphere, oceans, and water, snow and ice stored on land, causes the Earth's gravity to change, causes the Earth's rotation to change by changing the Earth's inertia tensor, and causes the Earth's shape to change by changing the load acting on the solid, but not rigid, Earth. In fact, on time scales of months to a decade, loading of the solid Earth by surface fluids dominates non-secular variations in each of these three fundamental properties of the Earth. Since the gravity, rotation, and shape of the Earth all change in response to changes in the surface mass load, measurements of these quantities must be consistent with each other. Here, degree-2 spherical harmonic coefficients of the surface mass density inferred from independent gravity, rotation, and shape measurements spanning April 2002 to May 2005 at monthly intervals are compared to each other and to a model of the surface mass density obtained by summing the contributions of atmospheric pressure, ocean-bottom pressure, land hydrology, and a mass-conserving term. In general, the independent estimates of the surface mass density are found to be quite consistent with each other and with the model, with correlations being as high as 0.87 and with the model explaining as much as 88% of the observed variance. -------------------------------------------------------------------------------- Séminaires généraux de l'Institut de Physique du Globe de Paris --------------------------------------------------------------------------------