To gain insight into the question of ice sheet stability and sea level change in the face of global warming, scientists have turned to studying warm periods in the geologic past. The Last Interglacial (LIG), ~125 ka, has been of particular interest in this regard since atmospheric CO2 concentrations during the LIG were comparable to pre-industrial values and temperatures were consistent with simulations of 1-2º global warming.

Estimating peak global mean sea level, or equivalently minimum ice volumes, during the Last Interglacial requires that the elevation of local sea level records be corrected for processes that distort local sea level relative to the global average. One such process is glacial isostatic adjustment (GIA), which is the change in topography that occurs due to the loading (or unloading) of the Earth with ice and water. Studies that have taken this process into account conclude that LIG global mean sea level peaked 6-9m above present-levels.

In this talk I will address previously unrecognized uncertainties in the GIA correction that stem from our incomplete knowledge of the temporal evolution of ice sheets prior to and during the LIG. I will further talk about the role of dynamic topography in deforming and biasing the LIG sea level record globally. 

Dynamic topography is the topography that is supported by viscous flow and buoyancy variations in the Earth’s mantle. To date, this global scale process has been ignored in sea level studies of Pleistocene interglacials, including the LIG, under the assumption that the signal would be negligible. I will show that modeled deflections span several meters, that they are significantly correlated with observed sea level highstands and that they are consistent with construction and preservation attributes across different sea level indicator types.