THE RELATIONSHIP BETWEEN TERRESTRIAL ICE SHEET MARGINS AND MEAN SUMMER TEMPERATURE FROM FULLY COUPLED ICE AND CLIMATE MODELLING (Invited Presentation)

Terrestrial paleoclimate records offer a potential constraint on past ice sheet evolution. However, our observational picture of the relation between ice sheets and climate is limited by fuzzy paleo data. It is also biased by present-day ice sheets that are not growing nor (yet) significantly retreating, at least in comparison to the inferred rates of retreat for the North American and Eurasian ice complexes during the last deglaciation. Our model-based window on the past is also biased. Relevant studies with advanced climate models have generally employed imposed ice sheet chronologies. For such studies, it is very unlikely that the ice sheet chronologies are self-consistent with the climate. Paleo ice sheet models forced by specified paleoclimate chronologies are similarly problematic given that the climate forcing is also very unlikely to be self-consistent with the ice sheet.

To more accurately quantify this ice margin and climate relationship, we analyze fully coupled transient ice and climate simulations of the last glacial inception (including the post-stadial retreat). We use the LCice model, which includes the LOVECLIM earth system model of intermediate complexity and the 3D thermo-mechanically coupled Glacial Systems Model. To partially address uncertainties, this analysis is carried out with an ensemble of over 100 simulations using different model parameters. Furthermore, these simulations have been selected from a larger ensemble according to consistency with inferred mean global sea level history over this interval. Such consistency is a challenging constraint for fully coupled models.

More generally, such fully (two-way) coupled ice and climate modelling enables the introduction of terrestrial paleoclimate constraints on past ice sheet evolution. This is especially of value for times prior to last glacial maximum for which constraints from glacial geology are much more limited.