Mass balance, flow, and subglacial processes of a modelled Younger Dryas ice cap in Scotland
ABSTRACT. We use an empirically validated high-resolution three-dimensional ice sheet model to investigate the mass balance regime, flow mechanisms, and subglacial character-istics of a simulated Younger Dryas stadial ice cap in Scotland, and compare the resulting model forecasts with geological evi...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.629.5626 http://nora.nerc.ac.uk/7909/1/JGLAC_08J014_R1_small.pdf |
| Summary: | ABSTRACT. We use an empirically validated high-resolution three-dimensional ice sheet model to investigate the mass balance regime, flow mechanisms, and subglacial character-istics of a simulated Younger Dryas stadial ice cap in Scotland, and compare the resulting model forecasts with geological evidence. Input data for the model are basal topography, a temperature forcing derived from GRIP δ18O fluctuations, and a precipitation distribution interpolated from modern data. The model employs a Positive Degree Day scheme to calcu-late net mass balance within a domain of 112500 km2, which under the imposed climate gives rise to an elongate ice cap along the axis of the western Scottish Highlands. At its maximum, the ice cap is dynamically and thermally zoned, reflecting topographic and climatic controls respectively. In order to link these palaeoglaciological conditions to geological interpreta-tions, we calculate the relative balance between sliding and creep within the simulated ice cap; forecast areas of the ice cap with the greatest capacity for basal erosion; and predict the likely pattern of subglacial drainage. We conclude that ice flow in central areas of the ice cap is a largely due to internal deformation, and is associated with geological evidence of landscape preservation. Conversely, the distribution of streamlined landforms is linked to faster-flowing ice whose velocity is predominantly the result of basal sliding. The geometry of the main ice mass focusses subglacial erosion in the mid-sections of topographic troughs, and produces glaciohydraulic gradients that favour subglacial drainage through low-order arterial routes. |
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