  Simulations of the Greenland Ice Sheet are carried out with a high-resolution
version of the ice-sheet model SICOPOLIS for several global-warming scenarios
for the period 1990-2350. In particular, the impact of
surface-meltwater-induced acceleration of basal sliding on the stability of the
ice sheet is investigated. A parameterization for the acceleration effect is
developed for which modelled and measured mass losses of the ice sheet in the
early 21st century agree well. The main findings of the simulations are: (i)
the ice sheet is generally very susceptible to global warming on time-scales of
centuries, (ii) surface-meltwater-induced acceleration of basal sliding leads
to a pronounced speed-up of ice streams and outlet glaciers, and (iii) this
ice-dynamical effect accelerates the decay of the Greenland Ice Sheet as a
whole significantly, but not catastrophically, in the 21st century and beyond.
