The geothermal output of the Katla caldera estimated using DEM differencing and 3D iceflow modelling

To estimate heat output from several cauldrons on Mýrdalsjökull ice--cap between the years 2016 and 2019, elevation changes from digital elevation models (DEMs) of the glacier surface, deduced from Pléiades optical satellite images, are compared with simulated topographical changes of the glacier surface over the same time period. The simulation solves for ice flow using a Full-Stokes finite element model. Based on the estimated ice flow velocities the free surface of the glacier is transported in the flow over time. An inequality constrained solution procedure is used to enforce the naturally occurring boundary condition that the surface elevation of a glacier can not fall below the elevation of its bedrock. Utilizing the computed topographical changes in a comparison with DEM data allows for an estimate of ice volume change differences. These differences are attributed to basal melting beneath each respective cauldron because the simulations do not include basal processes. Based on these volume change differences estimates of the required amount of heat energy to melt the missing ice volumes can be calculated.