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Dutch title: Antarctische Subglaciale Processen en Interacties: de rol van transitiezones in ijskapstabiliteit|
Parent project: Science for a Sustainable Development, more
Reference no: SD/CA/02A
Period: December 2005 till December 2007
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- Vrije Universiteit Brussel; Faculteit Wetenschappen; Vakgroep Geografie (VUB), more, co-ordinator
- Université Libre de Bruxelles; Faculté des Sciences; Département des Sciences de la Terre et de l'Environnement; Laboratoire de Glaciologie, more, partner
- Vrije Universiteit Brussel; Faculteit Wetenschappen & Bio-ingenieurswetenschappen; Vakgroep Geografie; Onderzoeksgroep Fysische Geografie (FARD), more, partner
ASPI (Antarctic Subglacial Processes and Interactions: the role of transition zones in ice sheet stability) is an interdisciplinary research project that focuses on the stability of marine ice sheets, ice shelves and subglacial lakes within a global climate change context. ASPI forms part of the Belgian ACSYS/CliC-related activities and is part of the IPY endorsed research programme SALE-UNITED (Subglacial Antarctic Lake Environments). ASPI is the follow-up of AMICS (Antarctic ice sheet dynamics and climate change: Modelling and Ice Composition Studies).
The aim of ASPI is (i) to understand the interactions between the ice sheet and the subglacial environment and the processes that control the Antarctic ice sheet, and (ii) to quantitatively determine the stability of the ice sheet in a changing climate and the impact of climatic variations on the coastal ice sheet. A key factor in such quantification and impact assessment is the existence of transition zones within the ice sheet. Typical examples of such transition zones are the grounding lines, i.e. the interface between the ice sheet and an ice shelf, between an ice sheet and a subglacial lake, as well as between an ice shelf and its pinning points. These transition zones are probably among the least understood elements of ice sheets, although they determine to a large extent the processes and dynamics of lateral expansion and retreat of ice sheets as well as the stability of marine ice sheets.
Work Package 1: Grounding line migration
In most large scale ice sheet models of the Antarctic ice sheet, transition zones at the grounding line are considered to be small in extent and hence smaller than the grid size used in these models. However, in ice streams, transition zones are several hundreds of kilometres large, even for continental ice streams that drain large parts of the East Antarctic ice sheet. The need to elaborate models that treat both the mechanical coupling between ice shelf and ice sheet and simulate the migration of the grounding line in an appropriate way became clear after the recent observed grounding line retreat (Rignot, 1998) and inland thinning of Pine Island Glacier (PIG; Shepherd et al., 2004), due to rapid upstream thinning propagation. These studies thus imply a tight coupling between the ice sheet interior and surrounding ocean. ASPI intends to shed a light on both mechanisms of stress transmission and grounding line migration in a marine ice sheet for different perturbations in both the ice shelf and at the grounding line with a higher-order ice sheet model. Our treatment would use a sub-grid accuracy determination of the grounding line and a full 3D determination of the stress field across the grounding line (transition zone), leading to a proper grounding line migration in the plane.
Work Package 2: “Welding” at grounding lines by marine ice formation
Transition zones at grounding lines are the seat of marine ice formation in the large-scale bottom crevasses occurring at the hinge and between individual ice streams getting afloat. Marine ice thus has a great potential to stabilize the ice shelf flow, especially at those transition zones where the ice gets afloat (grounding line) and where it impinges on pinning points. Pinning points are considered to be equally important in stabilizing the ice flow in ice shelves and ice sheets. In January 2005, a deep ice core was retrieved within the framework of the (French-British) Berkner Island Ice Core Drilling Project (Dr. R. Mulvaney, pers. com.). Bedrock has been reached at 948.5 m depth and the bottom of the core consists of more than two metres of debris-loaded ice. This would provide the first opportunity to investigate the ice-substrate interface of an island which acts as a major pinning point for the Filchner-Ronne Ice shelf. ASPI proposes to study these mechanical properties of ma