Shallow-earth rheology from glacial isostasy and satellite gravity

Abstract

In recent years, satellite gravity missions have been launched that probe the earth's long- to mediumwavelength (1000 - 500 km) gravity field. The upcoming ESA satellite gravity mission GOCE is predicted to measure the gravity field with an accuracy of a few centimeters at spatial scales of 100 km. Such a high-resolution gravity field contains information on mass inhomogeneities in the shallow earth, for example due to the creep of low-viscosity material forced by the growth and decay of ice sheets during the last glacial cycle. In this PhD thesis we show that GOCE is predicted to be sensitive to crustal low-viscosity zones down to a resolution of 150 km, but that recovery of the long wavelengths is hampered by uncertainties in the background earth stratification and ice-load history. We develop a thermomechanical earth model and show that creep laws and heatflow data can be used as additional constraints on the rheology of the shallow earth. Finally we indicate how in the near future high-resolution information on the shallow earth and the ice-load history can be obtained from GOCE and how this information can be used to improve for example estimates of present-day sea-level change.