The evolution of the Greenland Ice Sheet from the Last Glacial Maximum to present-day: An assessment using glaciological and Glacial Isostatic Adjustment modelling
In this thesis we constrain a three-dimensional thermomechanical model of Greenland ice sheet (GrIS) evolution from the Last Glacial Maximum (LGM, 21 ka BP) to the present-day using, primarily, observations of relative sea level (RSL) as well as field data on past ice extent. The new model (Huy2) fi...
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| Format: | Thesis |
| Language: | unknown |
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2009
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| Online Access: | http://etheses.dur.ac.uk/283/ http://etheses.dur.ac.uk/283/1/M.Simpson,_PhD_thesis.pdf |
| Summary: | In this thesis we constrain a three-dimensional thermomechanical model of Greenland ice sheet (GrIS) evolution from the Last Glacial Maximum (LGM, 21 ka BP) to the present-day using, primarily, observations of relative sea level (RSL) as well as field data on past ice extent. The new model (Huy2) fits a majority of the observations and is characterised by a number of key features: (i) the ice sheet had an excess volume (relative to present) of 4.1 m ice-equivalent sea level at the LGM, which increased to reach a maximum value of 4.6 m at 16.5 ka BP; (ii) retreat from the continental shelf was not continuous around the entire margin, as there was a Younger Dryas readvance in some areas. The final episode of marine retreat was rapid and relatively late (c. 12 ka BP), leaving the ice sheet land based by 10 ka BP; (iii) in response to the Holocene Thermal Maximum (HTM) the ice margin retreated behind its present-day position by up to 80 km in the southwest, 20 km in the south and 80 km in a small area of the northeast. As a result of this retreat the modelled ice sheet reaches a minimum extent between 5 and 4 ka BP, which corresponds to a deficit volume (relative to present) of 0.17 m ice-equivalent sea level. The results suggest that remaining discrepancies between the model and the observations are likely associated with non-Greenland ice load, differences between modelled and observed present-day ice elevation around the margin, lateral variations in Earth structure and/or the pattern of ice margin retreat. Predictions of present-day vertical land motion generated using the new Huy2 model are highly sensitive to variations of upper mantle viscosity. Depending on the Earth model adopted, different periods of post-LGM ice loading change dominate the present-day response in particular regions of Greenland. These results will be a useful resource when interpreting existing and future observations of vertical land motion in Greenland. In comparison to the sparse number of GPS observations available, predictions from ... |
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