More Ice in Warmer Worlds? Reassessing Plio-Pleistocene Climate Relationships

Paleoproxy records of bottom water temperature (BWT) have been used to investigate past reconfigurations of ocean circulation, infer changes in global ice volume following deconvolution of benthic oxygen isotopes, and extract information about average surface climate in warm, equilibrated states. Despite the wealth of BWT data available for the past 5 Myrs, persisting uncertanties in the proxy systems and methods most widely used to derive BWT have led to different, at times conflicting, views of climate and sea level variability across key Plio-Pleistocene transitions. Here we present ongoing work to better constrain the long-term evolution of Plio-Pleistocene BWTs using clumped isotopes from benthic foraminifera, bypassing well-known pitfalls affecting other temperature indicators and opening new avenues of leverage in multiproxy comparisons. Our results question previous definitions of the relationship between mean ocean BWTs and global ice volume, with puzzling implications  for the so-called intensification of Northern Hemisphere glaciations after the mid-Piazencian Warm Period and the expected influence of ice-sheets on global climate. Moreover, these new records support the use of mean ocean BWT as a reflection of average surface climate beyond the Miocene, thereby showing great potential to inform the development of new paleo-informed climate models.