Understanding the source of glacial earthquakes : mechanical modeling of capsizing icebergs and generated water motion

One current concern in climate science is the estimations of the amount of ice loss by glaciers each year and the corresponding rate of sea level rise. Greenland ice sheet contribution is significant with about 30% to the global ice mass losses. Ice loss in Greenland is distributed approximately equally between loss in land by surface melting and loss at the front of marine-terminating glaciers that is modulated by dynamic processes. Dynamic mass loss includes both submarine melting and iceberg calving.

The processes that control ablation at tidewater glacier termini, glacier retreat and calving are complex, setting the limits to the estimation of dynamic mass loss and the relation to glacier dynamics. It involves interactions between bedrock - glaciers - icebergs - ice-mélange - water - atmosphere. We aim to improve the understanding of iceberg capsize using a mechanical modeling of iceberg rotation against the glacier terminus, constrained by the generated seismic waves that are recorded at teleseismic distances. To achieve this objective, we develop a fluid-structure interaction model for the capsizing iceberg. Full scale fluid-structure interaction models enable accurate simulation of complex fluid flows in presence of rigid or deformable solids and in presence of free surfaces. However, such models are computationally very expensive. Therefore, our strategy is to construct a simple solid dynamics model involving contact and friction, whose simplified interaction with water is governed by parametrized forces and moments. We fine tune these parametrized effects on an iceberg capsizing freely in open ocean with the help of a reference direct numerical simulations of fluid-structure interactions involving full resolution of Navier-Stokes equations and validated on experimental data. The seismogenic sources of the capsizing iceberg simulated with our model are then compared to the recorded seismic signals. The volume of capsizing icebergs over 1993-2013 period have been previously estimated with a similar model, the improved model allows to refine these estimations.