Glaciological Implications of Misfits in Radar Layer Geometry Modelling

• Main Authors: Leysinger Vieli, G, Hindmarsh, R, Siegert, MJ
• Format: Other Non-Article Part of Journal/Newspaper
• Language: English
• Published: 2005
• Subjects: East Antarctica; Antarc*; Antarctica; Ice Sheet
• Online Access: http://hdl.handle.net/1983/c6e99fdc-a02f-4532-a6f7-00bd57dbb4c3; https://research-information.bris.ac.uk/en/publications/c6e99fdc-a02f-4532-a6f7-00bd57dbb4c3; http://www.agu.org

Direct measurements of ice sheet mass balance have rarely been acquired in East Antarctica. Past rates of ice accumulation are even less well known. The positions of isochronous englacial layers, measured by radio-echo sounding (RES), are influenced by several processes, including past accumulation. We use a three dimensional ice flow model to deduce past accumulation rates from layering, measured from the most extensive RES survey of East Antarctica (undertaken during several field seasons in the 1970s). The model generates velocities from modern balance fluxes, and the age equation is solved to generate ages and isochrone geometry. Under an assumption that the accumulation rate can be separated into temporal and spatial components, time dependent spatially varying accumulation rates can be deduced. The large RES-layer dataset we use has never previously been modelled, let alone in 3D, so the types of problems that might be encountered are not yet clear. Therefore, our objectives are: 1) to establish the quality of the match between model input and data; 2) to determine how easy systematic alteration of the accumulation rate is to improve the quality of the model output; 3) to investigate the importance of the mechanics of short wavelength topography on the ice flow. Nevertheless, we are confident that mismatches of a length-scale larger than approximately 50-100 km can be explained by either a misfit in current accumulation or by some flow features (i.e. ice stream) which are not considered in the model. Direct measurements of ice sheet mass balance have rarely been acquired in East Antarctica. Past rates of ice accumulation are even less well known. The positions of isochronous englacial layers, measured by radio-echo sounding (RES), are influenced by several processes, including past accumulation. We use a three dimensional ice flow model to deduce past accumulation rates from layering, measured from the most extensive RES survey of East Antarctica (undertaken during several field seasons in the 1970s). The model generates velocities from modern balance fluxes, and the age equation is solved to generate ages and isochrone geometry. Under an assumption that the accumulation rate can be separated into temporal and spatial components, time dependent spatially varying accumulation rates can be deduced. The large RES-layer dataset we use has never previously been modelled, let alone in 3D, so the types of problems that might be encountered are not yet clear. Therefore, our objectives are: 1) to establish the quality of the match between model input and data; 2) to determine how easy systematic alteration of the accumulation rate is to improve the quality of the model output; 3) to investigate the importance of the mechanics of short wavelength topography on the ice flow. Nevertheless, we are confident that mismatches of a length-scale larger than approximately 50-100 km can be explained by either a misfit in current accumulation or by some flow features (i.e. ice stream) which are not considered in the model.