Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing
The majority of Antarctic ice shelves are bounded by grounded ice rises. These ice rises exhibit local flow fields that partially oppose the flow of the surrounding ice shelves. Formation of ice rises is accompanied by a characteristic upward-arching internal stratigraphy (“Raymond arches”), whose geometry can be analysed to infer information about past ice-sheet changes in areas where other archives such as rock outcrops are missing. Here we present an improved modelling framework using Elmer/Ice to study ice-rise evolution using a satellite-velocity calibrated, isothermal, and isotropic 3-D full-Stokes model including grounding-line dynamics at the required mesh resolution (<500 m). This overcomes limitations of previous studies where ice-rise modelling has been restricted to 2-D and excluded the coupling between the ice shelf and ice rise. We apply the model to the Ekström Ice Shelf, Antarctica, containing two ice rises. Our simulations investigate the effect of surface mass balance and ocean perturbations onto ice-rise divide position and interpret possible resulting unique Raymond arch geometries. Our perturbation simulations for the Ekström catchment reveal that SMB perturbations result in fast divide migration (up to 3.5 m /a), while shelf thickness perturbations only trigger slow divide migration (< 0.75 m /a). The amplitude of divide migration is predominately controlled by the subglacial topography and SMB, with ice-shelf buttressing being of secondary importance. We also track the migration of a triple junction and synchronous ice-divide migration in both ice rises with similar magnitude but differing rates. The model is suitable for glacial/interglacial simulations on the catchment scale, providing the next step forward to unravel the ice-dynamic history stored in ice rises all around Antarctica.
Read more: Schannwell C., R. Drews, T.A. Ehlers, O. Eisen, C. Mayer and F. Gillet-Chaulet, 2019. Kinematic response of ice-rise divides to changes in ocean and atmosphere forcing, The Cryosphere, 13, 2673–2691, DOI: 10.5194/tc-13-2673-2019.