Coupling between the Antarctic ice flow, subglacial regimes and regional climate conditions

• Main Author: Bernales, J.
• Format: Doctoral or Postdoctoral Thesis
• Language: unknown
• Published: Freie Universität 2018
• Subjects: Antarctic; Southern Ocean; The Antarctic; Antarc*; Ice Sheet; Ice Shelf; Ice Shelves; Iceberg*
• Online Access: https://gfzpublic.gfz-potsdam.de/pubman/item/item_2911894; https://gfzpublic.gfz-potsdam.de/pubman/item/item_2911894_5/component/file_2915888/thesis_v00_hyperlinks.pdf

The Antarctic ice sheet is part of an intricate feedback system that includes the solid Earth, the atmosphere, and the ocean. A deep understanding of the interactions between these sub-systems would path the way for improved reconstructions of the Antarctic ice dynamics during past periods, particularly when global climate conditions were similar to those expected in the upcoming centuries. However, the acquisition of observational data needed to strip some of the key ice sheet processes, such as basal ice sliding modulated by the presence of water and soft earth materials, has proven to be difficult due to the particular remoteness and harsh climate conditions of the Antarctic continent. This thesis interconnects three scientific papers to demonstrate that uncertainties in subglacial regimes may explain commonly large discrepancies between the model-based and observed dynamical states of the present-day Antarctic ice sheet and that model-based reconstructions of these regimes can be used to reveal biases in the external forcing. Until now, most of ice sheet modelling studies have either relied on simplified representations of basal sliding that assume homogeneous bedrock conditions or employed inferences from previous studies as boundary conditions. Using an automated calibration technique of a continental-scale ice-sheet model, the first scientific paper within this thesis deciphers subglacial sliding regimes under the Antarctic ice sheet and shows that they are likely highly heterogeneous across the Antarctic continent. They also appear sensitive to differences in model formulations implying that a direct transfer of such reconstructions from a different model is ill-fated. Ice shelves respond strongly to the thermal regime of the Southern Ocean that modulates iceberg calving and sub-shelf melting, with the latter being the largest source of ice loss from the Antarctic ice sheet at present. Thus, an accurate representation of ice-shelf basal melting regimes is key to realistic modelling of the Antarctic ice ...