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Abstract:
One task of the German National Climate Modeling Initiative PalMod will be to couple earth system models
representing the atmospere, ocean and ice dynamics during the last glacial cycle with the dynamic loading response
of a viscoelastic earth model. In preparation, we discuss in this study the influence of viscosity stratification and of
lateral heterogeneities in the Earth structure on the solid-earth response to glacial loading.
As discussed in literature, there is a controversy about the impact of lateral heterogeneity on the prediction of
present and past GIA signals. The influence of the Earth structure on the far-field response is governed by the
flexural behaviour of the regional lithosphere and upper-mantle structure in response to the varying ocean load.
The influence at and around the glacial ice sheets is substantial with respect to the amplitudes and also with respect
to the temporal evolution of the earth’s response. Depending on the region of interest, lithospheric variations are
present over the extent of the glacial ice sheets varying between 40 and 200 km, and lateral variations in viscosity
can vary by one or two orders of magnitude.
The focus will be to what extent the behaviour of a laterally heterogeneous viscosity structure can be parameterised
by an adjusted spherical earth model representation. Accordingly, we apply predefined ice-sheet histories
(like ICE5G and ICE6G) and analyse ensemble runs representing the variability of relative sea-level and palaeotopography
predictions. Spatial pattern of deformation fields will be discussed as the behaviour at specific sea-level
curves. Furthermore, we compare the sensitivity on earth structure during the evolution of sea level and palaeo topography
during the termination phase of the last glaciation to present-day rates of relative sea-level height and
radial displacement.
