Sea-level stands from the Western Mediterranean over the past 6.5 million years

Oana A Dumitru,Jacqueline Austermann,Bogdan P Onac,Angel Ginés,Victor J Polyak,Joaquín Ginés,Joan J Fornós,Yemane Asmerom

doi:10.1038/s41598-020-80025-6

Abstract

Sea-level reconstructions are important for understanding past ice sheet variability and its response to past and future warming. Here we present Neogene and Quaternary sea-level snapshots using phreatic overgrowths on speleothems (POS) from caves on Mallorca, Spain. POS are excellent sea level index points because of their clear relationship to sea level and precise U–Pb chronology. We find that local sea-level before and at the onset of the Messinian Salinity Crisis was at 33.3 ± 0.25 m (6.54 ± 0.37 Ma) and 31.8 ± 0.25 m (5.86 ± 0.60 Ma) above present levels, respectively. We further present global mean sea level (GMSL) estimates, i.e. local sea level corrected for glacial isostatic adjustment and long-term uplift, for three other POS. The results show that GMSL during the Pliocene–Pleistocene Transition was 6.4 m (− 2.0–8.8 m) at 2.63 ± 0.11 Ma and during the beginning and the end of the Mid-Pleistocene Transition was − 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 show that local sea level prior to the MSC was similar to the highest stand during the Pliocene, with markedly lower position afterwards.

Highlights

Accurate projections of future sea-level change rely on a thorough understanding of the mechanisms driving its complex spatio-temporal e volution[1]
In this study we focus on sea level in the Mediterranean over the past 6.5 Myr, which experienced changes due to Milankovitch cycles, continuous cooling into the present-day ice age, and was punctuated by the Messinian Salinity Crisis (MSC)[7,8]
The Messinian time period was followed by the Pliocene Epoch, which includes the Pliocene Climatic Optimum and the mid-Piacenzian Warm Period (MPWP), both intervals that have been considered as possible analogues for investigating ice sheet sensitivity in a warmer than present climate, since their atmospheric temperatures were ~ 4 and 2–3 °C, respectively, higher than preindustrial values[17,18]

Summary

Introduction

Accurate projections of future sea-level change rely on a thorough understanding of the mechanisms driving its complex spatio-temporal e volution[1]. Each approach to reconstructing Pliocene–Pleistocene global mean sea level has its advantages and disadvantages: records based on marine sediment cores are generally time continuous, they lack absolute chronologies and a clear relationship to past sea level. Geologic records, such as paleo-shorelines, can be dated more directly but only constrain local sea level, not the global ice-equivalent mean. These GMSL reconstructions can help validating numerical ice sheet models that we are largely reliant on when projecting future sea-level c hanges[4,32]. Studies over the past decade have demonstrated the suitability of POS as meaningful sea-level index points[6,34,35]

Methods

Results

Conclusion