RD&D-Programme 2004 - SKB

Figure 21-3. As an ice sheet advances and retreats, changes occur in temperature, hydrological
conditions, rock stresses and groundwater composition.
The geothermal heat flow and its variations have previously been judged to have an important
influence on the basal conditions of continental ice sheets, above all on basal ice temperatures
and meltwater production /21-10 to 21-12/. The temperature and quantity of water at the base
of the ice in turn influences the dynamics of the whole ice sheet. A dataset that describes the
spatial variation of the geothermal flow over Scandinavia has been compiled with the purpose
to, for the first time in ice sheet modelling, examine the effects of spatially varying geothermal
heat flow on basal conditions, as well as to determine a correct average value /21-13, 21-14/.
The dataset has been used for simulations of the Weichselian period with an ice sheet model
developed at the University of Maine in cooperation with Stockholm University /21-15 to
21-17/. The initial results show that the use of realistic geothermal data is important in
numerical modelling of the ice sheet’s basal conditions and the meltwater production in
the interface between the ice and its substrate /21-14/.
The thermohydromechanical effects of a continental ice sheet over a repository site have been
studied with the aid of different numerical models in the international Decovalex/Benchpar
project /21-18/. Data from the Whiteshell area in Canada have been used in the project, but
the results can in principle be considered to be representative for Swedish conditions as well.
An important conclusion of the modellings is that hydraulic and mechanical processes of
importance for the performance of the deep repository are coupled and that transient effects
are significant.
RD&D-Programme 2004 295