Decadal sea surface temperature variability in the Eastern Mediterranean during the Last Interglacial

MARUM, University of Bremen, Germany (1); Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Germany (2); University of Tübingen, Germany Precise future predictions of Mediterranean sea surface temperature (SST) variability as one of the most sensitive regions to climate change are hampered by insufficient knowledge of accurate SST reconstructions in resolution relevant for human time-scales from warmer-than-present periods. The Last Interglacial (LIG; ~130,000 to 116,000 years ago) is the most recent period with warmer-than-present climate; however, continuous subdecadal records of LIG SST are unavailable due to a small number of undisturbed sedimentary records and sample-size limitations of conventional methodologies. We circumvent these issues by applying Mass Spectrometry Imaging on finely laminated sapropel S5 sediment deposited in the Eastern Mediterranean; the result is an alkenone-based SST time-series in 1-4 year resolution. These data reveal prominent and rapid decadal SST oscillations in the Eastern Mediterranean with a ~60 years cyclicity that is persistent throughout most of the record, suggesting similar LIG decadal climate oscillations as in the Holocene. We also compare the reconstructed rate of SST change during the LIG to the present-day observational record, and find that LIG temperature change often exceeded the present-day rate of change. On the other hand, comparison of the LIG multidecadal SST to the projected increase in Mediterranean SST until 2100 AD suggests SST increase at the end of the 21st century to be unprecedented in magnitude and duration. We thus conclude that future warming of the Mediterranean could cause an unrivalled change in the Mediterranean planktonic ecosystems and their biological responses.