Recovering lateral variations in lithospheric strength from bedrock motion data using a coupled ice sheet-lithosphere model

A vertically integrated two-dimensional ice flow model was coupled to an elastic lithosphere-Earth model to study the effects of lateral variations in lithospheric strength on local bedrock adjustment. We used a synthetic bedrock profile and a synthetic climate to model a characteristic ice sheet through an ice age cycle. Realistic differences in lithospheric strength altered the local bedrock adjustment up to 100 m, the ice extent by tens of kilometers, and the ice volume by several percent. Hence, when modeling ice sheets, it is essential to include information on lithospheric structure. In addition, we used the coupled ice flow - lithosphere model to construct synthetic bedrock motion time series to assess their potential in resolving lithospheric structure. Inverse experiments showed that the model can resolve lateral variations in lithospheric strength from these bedrock motion time series, provided that we have data from both sides of a lateral transition in lithospheric strength. The inversion that solved for a lateral transition was able to find a solution that was consistent with all data, even if they were noisy. In the presence of lateral variations in lithospheric strength, there was no solution to the inverse problem for which all data were modeled correctly by a uniform lithospheric model. The synthetic data showed no significant sensitivity to the location of the transition. Hence we require information from independent sources, such as seismology or gravity, about the locations of transitions in lithospheric strength.