PLIOCENE-PLEISTOCENE SPELEOTHEM-BASED SEA LEVEL SNAPSHOTS FROM THE WESTERN MEDITERRANEAN (Invited Presentation)

Sea-level reconstructions are important for understanding past ice sheet variability and its response to past and future warming. Estimates of global mean sea level (GMSL), i.e. local sea level corrected for glacial isostatic adjustment and long-term uplift, during Pliocene and Pleistocene times exist, but they vary by several tens of meters, hindering the assessment of past and future ice-sheet stability. Here we present sea-level snapshots between 4.5 and 0.8 Ma using phreatic overgrowths on speleothems (POS) from caves on Mallorca, which is an island in the western Mediterranean. POS serve as excellent sea level index points because they have a clear relationship to mean sea level as they form in the tidal range and can be dated with the U-Pb method. We show that during the mid-Piacenzian Warm Period, which was on average two to three degrees Celsius warmer than the pre-industrial period, GMSL was about 17.4 m (6.8 – 20.3 m; 68% uncertainty range) higher than today owing to global ice-volume changes. During the even warmer Pliocene Climatic Optimum, our results indicate that the GMSL was 25.1 m (10.6 – 28.3 m) above the present level. We further find GMSL estimates for the Pliocene-Pleistocene Transition of 6.4 m (-2.0 – 8.8 m) and for the beginning and the end of the Mid-Pleistocene Transition of -1.1 m (-5.6 – 2.4 m) and 5 m (1.5 – 8.1 m), respectively. These estimates provide important constraints for the past evolution of sea level and they also yield calibration targets for future ice-sheet models and indicate that ice sheets are very sensitive to warming.