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Title: Modelling mid-Pliocene climate and ice sheets
Author: Dolan, Aisling Margaret
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2012
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Given anthropogenic modification of the climate system, the future stability of Earth's major ice sheets and sea level is uncertain. One potential, lJ1ethod to investigate the behaviour of the Greenland and Antarctic ice sheets under a warmer-than-modern climate regime, is to look back at past warm periods of Earth history (for example the mid Pliocene Warm Period; 3.26 - 3.0 million years ago). The British Antarctic Survey Ice Sheet Model (BASISM) and the Hadley Centre Coupled Climate Model version 3 (HadCM3) allow the climate and ice sheets of the mid-Pliocene to be modelled, and their sensitivity to a range of uncertainties in forcing to be quantified. The ice sheets, particularly the Greenland Ice Sheet, are sensitive to changes in the Earth's orbital configuration and potential levels of atmospheric carbon dioxide (C02) during the mid-Pliocene. Exploring various orbital forcing scenarios in concert with a plausible Pliocene COz envelope (280 - 560 ppmv), enables models to generate Greenland ice sheet reconstructions that range from a 1.5% reduction from modern to an ice-free state. In contrast, on East Antarctica, significant ice sheet retreat is only simulated under warm Southern Hemisphere orbital conditions where C02 levels are at 400 ppmv or above. Maximum eustatic sea level rise corresponding to predicted ice sheet reductions is comparable with recent records suggesting mid-Pliocene sea level high-stands of 22 m greater than modern. However, ice sheet reconstructions are shown to be highly dependent on Q priori assumptions regarding the initial ice sheet configuration within the numerical modelling framework. Investigation of the dependency of ice sheet predictions on the models used, has demonstrated that results are sensitive to the modelled climatological forcing. Such dependency is most explicitly highlighted over Greenland, where Pliocene ice sheet predictions, given forcings from fifteen equivalently-configured climate models, range from no ice to a configuration that is larger than modern. These results underline the importance of considering mUltiple sources of uncertainty when predicting past ice sheets. v
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available