The Antarctic Ice Sheet during the Last Interglacial: what does it really tell us about the ice sheet’s future?

The warm climate of the Last Interglacial (LIG; ~130-118 ky before present) is often considered as an analogue for future warming. Although global mean warming is limited to about 0.5-1°C, it is often suggested that a casual relationship exists with a substantial volume loss of the Antarctic ice sheet (AIS), as inferred from a 6-9 global sea-level rise. However, there are indications from the geological record that this picture is an oversimplification, possibly implying that the analogy between the LIG AIS evolution and future fate of the AIS should be looked at from a different angle. In the proposed research I will use an Earth system model to assess which picture is in best correspondence with both geological evidence and our physical understanding of the Earth system. I will investigate pictures of the LIG AIS evolution as: i) an equilibrium response to temperature change; ii) a transient response to the deglaciation including a collapse of the large-scale ocean overturning circulation; or iii) resulting from the AIS crossing a tipping point as a consequence of a very rapid deglaciation.
In this work I will use the Earth system model iLOVECLIM and introduce a coupling between the AIS and the surrounding oceans waters using a recently developed sophisticated parametrization scheme. Taking advantage of the computational efficiency of the model, I will create a large ensemble of perturbed physics and perturbed initial conditions simulation. This will allow me to cover the full uncertainty space of key processes and investigate the role of stochastic processes for the LIG’s evolution.
The fact that crucial information on the LIG AIS evolution comes from very different geological archives has thus far inhibited an in-depth model-data comparison. Because of the capability of iLOVECLIM to directly simulate many geological records, such as oxygen and carbon isotopes, ocean circulation proxies like Pa/Th, icebergs and sea-level changes, I will be able to incorporate all key geological information. Only by combining all the above ingredients can we deduce what the LIG can teach us about the future fate of the AIS.