In this AURORA DIFFOBRES project, together with the French LSCE team led by Gilles Ramstein, we will collaborate to develop a new project under the structure of Pliocene Model Intercomparsion Project (PlioMIP), in order to investigate the warm Pliocene cl imate. We intend to understand the mechanism behind a new shift in the climate response to orbital changes, in particular obliquity changes, in the transition from the Pliocene warm world that the cryosphere played a minor role to the Pleistocene cold wor ld (as our present day climate) that huge variations of the cryosphere occurred.
During the Pliocene and the early-mid Pleistocene (~5-1 Ma), global ice volume, as given by the global benthic ?18O stack, matches the obliquity variability of insolation wi th a period of ~41kyr. However, the amplitude of global ice volume changes increased significantly towards the Early-Mid Pleistocene (~3-1 Ma). Why was the global benthic ?18O response to similar obliquity changes different during the Pliocene in relative to the early-mid Pleistocene? This question is interesting and important for understanding past climate variation on the orbital time scale, but often neglected.
In this project, we will use climate models and ice sheets models to carry out numerical ex periments, to test if land/sea ice or ocean states can lead to different climate responses to an identical obliquity change. If the ocean state is found to have significantly modulated insolation forcing, it is possible that climate sensitivity will also be different. As the Pliocene is often considered to be an analogy for our future climate, this study will produce new knowledge on climate sensitivity that will be essential for a meaningful understanding of future climate change.