|dc.description.abstract||The aim of this project is to improve our understanding of the past European and
British ice sheets as a basis for forecasting their future. The behaviour of these ice
sheets is investigated by simulating them using a numerical model and comparing
model results with geological data including relative sea–level change data. In
order to achieve this aim, a coupled ice sheet/lithosphere model is developed.
Ice sheets form an integral part of the Earth system. They affect the planet’s
albedo, atmospheric and oceanic circulation patterns, topography, and global
and local sea–level change. In order to understand how these systems work, it is
necessary to understand how ice sheets interact with other parts of the climate
system. This project does this by simulating ice behaviour as part of the climate
system and evaluating model behaviour in relation to evidence of past ice sheets.
Ice sheet simulations can be treated with more confidence if they can be
evaluated against independent data. A methodology is therefore developed
that compares relative sea–level records with simulations of past sea–level which
result from modelling past ice sheets with a dynamic, high–resolution thermo–
mechanical ice sheet model coupled to an isostatic adjustment model. The Earth’s
response to changing surface loads is simulated using both a regional, flat Earth
approximation and a global, spherical self–gravitating Earth model.
The coupled model is tested by initially simulating the past Fennoscandian ice
sheet because of the simpler topographic framework and the quality of geological
evidence of past fluctuations against which to evaluate model behaviour. The
model is driven by a climatic forcing function determined so that the simulated
ice sheet resembles the past Fennoscandian ice sheet as reconstructed from
geomorphological evidence. The Fennoscandian climate driver is then transferred
to the British Isles to simulate the past British ice sheet. Finally, a non–linear
regression technique is used to construct future ice sheet drivers from future sea–
level change scenarios to forecast sea–level change around the British Isles during
the next glacial cycle.
The data used for the inversion procedure is limited to southern Scandinavia.
Outside this area, the simulation compares poorly with reconstructions based on
geological observations. However, model fit within this region is good and the
simulation is also in good agreement with features not used during the inversion
process. This approach illustrates the benefit of using a model coupling realistic
ice physics to a realistic Earth model to help constrain simultaneously unknowns of Earth rheology and ice thickness. Ultimately, relative sea–level data together
with other strands of data, such as geomorphological evidence, and a coupled ice
sheet/isostatic rebound model can be used to help infer past climates.||en