Predictions of Deformation and Gravity Change Caused by Recent Melting of the Vatnajökull Ice Cap, Iceland

Abstract

The recent episode of climate warming has resulted in a decrease in volume of the Vatnajökull ice cap, south-eastern Iceland, during this century. In view of the small lithosphere thickness and the low asthenosphere viscosity below Iceland, this deloading process is expected to result in observable deformation in the vicinity of the ice cap. In 1991, GPS and gravity campaigns were initiated in order to record this deformation. The network is situated south-east of the ice cap and extends from its margin to a distance of ≃ 70 km

In the present study, we predict rates of uplift, radial displacement and gravity change induced by the recent deloading. The calculations are based on plane three-layer Maxwell-viscoelastic earth models and an axisymmetric load model with elliptic cross-section. The results show that, for a lithosphere thickness of 10 km and an asthenosphere viscosity of 5 × 10¹⁸ Pa s, the rate of uplift near the ice margin reaches ≃8mm a⁻¹, whereas the rate of radial displacement is≃−1 mm a⁻¹. The corresponding rate of gravity change is predicted to be ≃−1.4μGal a⁻¹. For higher asthenosphere viscosities, all rates are significantly reduced.