Talk by Andreas Born, University of Bern

Titel: "Isochronal ice sheet model: A new approach to englacial tracer

The full history of ice sheet and climate interactions is recorded in
the vertical profiles of isotopic and other geochemical tracers in polar
ice sheets. In addition, recent advances in radiostratigraphy uncover
the englacial layering that contains information of past surface
topographies and thus ice sheet volumes and sea level. Numerical
simulations of these archives could afford great advances both in the
interpretation of these tracers as well as to help improve ice sheet
models themselves. However, fundamental mathematical shortcomings of
existing ice sheet models subject tracers to spurious diffusion,
thwarting efforts that employ straightforward solutions. Here, I propose
a new vertical discretization for ice sheet models that eliminates
numerical diffusion entirely. Vertical motion through the model mesh is
avoided by mimicking the real-world ice flow as a thinning of underlying
layers. A new layer is added to the surface at equidistant time
intervals, isochronally. Therefore, each layer is uniquely identified by
the time of deposition and hence by age. Horizontal motion follows the
shallow-ice-approximation. The new model approach is implemented for a
two-dimensional section through the summit of the Greenland ice sheet.