The present rate of uplift of Fennoscandia implies a low‐viscosity asthenosphere

The rate of displacement in Fennoscandia has been intensively discussed for many years. It is now widely accepted to be an isostatic response of the glacial history of the area. The Earth's present response to deglaciation in Fennoscandia is simulated using a three‐dimensional (3D), viscoelastic model in which the asthenosphere and mantle viscosity are allowed to vary so that the maximum rate of present uplift matches its observed value. The deglaciation history is considered to be known, and the C14‐datings are converted to sidereal years. The pattern of the present uplift gives a firm match with the observed data when a low‐viscosity asthenosphere is introduced. Assuming a 15,000 years load cycle, i.e. the glacier was applied to the surface for 15,000 years before the melting started, the best fitting earth viscosity model is a 1024 Nm lithosphere overlying a 75 km‐thick 2.0 × 1019 Pas asthenosphere and a 1.2 × 1021 Pas mantle. The simulations suggest a remaining maximum uplift of 40 m.