Modelling the dynamics of palaeo ice-stream retreat in Marguerite Bay, Antarctica
Abstract
The aim is to use numerical models of ice stream behaviour to understand the processes that triggered and controlled the retreat of the Marguerite Bay palaeo ice stream after the Last Glacial Maximum (LGM). This is important because at present a number of marine-based ice streams in Antarctica are rapidly losing mass. Given the consequences of this mass loss for future sea-level rise, it is crucial to improve our understanding and predictive abilities of grounding line retreat of marine-based ice streams. Because contemporary records of grounding line retreat are very short (decades) and may not be representative of behaviour on century or millennial timescales, we focus on the longer-term post-LGM retreat dynamics of the palaeo ice stream as recorded in the marine-geophysical record. Our approach combines numerical modelling with geomorphological mapping in order to understand the processes that triggered and controlled the hypothesized rapid retreat of the Marguerite Bay palaeo ice-stream. Here we describe the numerical model, modelling approach and results of sensitivity testing to understand the behaviour of the Marguerite Bay palaeo ice stream. High-resolution bathymetric data of the Marguerite Bay area has enabled detailed geomorphological mapping and provides a record of grounding line retreat. These mapping data, set into a chronological framework of deglaciation, are used to constrain a 1-dimensional flowline model of the Marguerite palaeo- ice-stream. The numerical model includes basal, lateral and longitudinal stresses and a robust treatment of grounding-line motion through the use of a constantly adjusting spatial grid. We subject the model to a range of external forcing including changes in sea-level, temperature and accumulation in order to reproduce the geomorphological evidence and therefore understand the dynamics of ice stream retreat in this area. We find that slow-downs or re-stabilisations of the grounding line occur in areas of reverse bed slope and that these grounding-line positions agree well with the locations of mapped grounding zone wedges in the mid-shelf zone of Marguerite Bay. The stresses included in the model, as well as the capability to adjust the resolution dynamically are important in achieving this agreement. Further, our modelling suggests meltwater pulse 1A as a likely key driver of the observed grounding line retreat pattern.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.C43C0557J
- Keywords:
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- 0730 CRYOSPHERE / Ice streams;
- 0774 CRYOSPHERE / Dynamics;
- 0798 CRYOSPHERE / Modeling