Postglacial induced surface motion and gravity in Laurentia for uniform mantle with power-law theology and ambient tectonic stress

Previous investigations of postglacial sea levels around Laurentia in a non -linear earth without ambient stress found that non-linear uniform mantle m odels cannot explain the relative sea level data around the ice margin. In this study, a 3D finite element model of postglacial readjustment is used t o calculate the Earth's response due to realistic ice and eustatic water lo ads on stratified mantle with non-linear theology and ambient tectonic shea r stress. Bp varying the creep parameter A* and the ambient stress level in a uniform mantle, it is found that the combination AY around 3 x 10(-35) P a-3 s(-1) and ambient stress level around 10 MPa is able to explain the sea level data both outside and inside the Laurentian ice margin - although fo r certain sites inside, a slightly thicker ice is required to improve the f it to the data. Other geophysical and geodetic observables - namely uplift rate, horizontal velocity, free air gravity and the rate of change of gravi ty - have also been calculated for this model. (C) 2001 Elsevier Science B. V. All rights reserved.