Ice-sheet modelling allows quantitative predictions of how large ice masses behave and respond to environmental change. As many different ice-sheet models were developed in the early 1990s, the EISMINT programme was set up to establish best practice and commonality within the field. Through intercomparison exercises, the EISMINT programme established appropriate controls on ice-sheet modelling. One of the results is the development of freely available ice-sheet modelling software, which can be used in future to help test geological hypotheses concerning past changes in Antarctica.

Although the large-scale behaviour of ice sheets can be reproduced well by numerical models, there are limitations to the accuracy of numerical ice-sheet modelling at a finer scale. This is because (1) ice-sheet models are derived from assumptions about the flow of ice which may not be accurate at all places in the ice sheet and (2) subglacial topography and other model inputs may be insufficiently well known to allow the model to work at a fine scale. The latter problem can be solved by obtaining high-resolution geophysical datasets of existing ice sheets to establish the subglacial topography, internal structure and surface elevation of the ice sheet. Such data acquisition has been ongoing for several decades.

Ice-sheet models have been used to comprehend past changes, and test hypotheses based on geological data. For example, Huybrechts (1993) showed that climate warming of over 15°C was required to decay the East Antarctic Ice Sheet into small discrete ice masses. As a result, the idea of restricted ice cover during the Pliocene was difficult to support by ice-sheet modelling. In additional exercises, Huybrechts (2002) revealed the sensitivity of the East and West Antarctic Ice Sheets to climate changes was noticeably different. In East Antarctica, the ice sheet appears resistant to even quite large changes, whereas modification to the size and shape of the West Antarctic Ice Sheet can be predicted with only small adjustments to boundary conditions. This sensitivity may characterize Antarctic glacial history throughout the Pleistocene and possibly much earlier.

Ice-sheet models are used to predict how the cryosphere responds to and affects climate change. From climate information gathered from ice cores, there is reason to believe that ice sheets, oceans and the atmosphere interact with each other. It is therefore important that ice-sheet models be coupled with models of atmospheric and ocean circulation in order to predict how the ice-ocean-atmosphere system behaves in the future and has behaved in the past (e.g. DeConto and Pollard, 2003). Examples of such coupling are provided in later chapters, and these activities mark a clear way for future reconstructions of past ice sheets in Antarctica.

0 0

Post a comment