High-resolution multi-proxy analysis on paleoclimatic changes in the Eastern Mediterranean during the Last Interglacial

Abstract

The climatic optimum during the last interglacial was the time interval during which the average sea level was ~5-6m higher, and more humid and warmer climate (by ~3°C from the present value) prevailed. However, studies done so far related to this period fail to provide any direct indicator of climate and environmental variability on annual to decadal timescales. Hence in this study, using recent advancements in molecular Mass Spectrometry Imaging, an ultra-high resolution reconstruction of the paleoenvironmental conditions ~125,000 years ago was done. Organic-rich sapropel S5 from the Eastern Mediterranean, formed during the last interglacial, comprises informative biomarkers like glycerol dialkyl glycerol tetraethers, alkenones and fatty acids, which were used to generate molecular stratigraphic records of their distribution. Uk’37 and CCaT paleothermometry generated from these biomarkers are indicative of sea surface temperature as well as oxygen limitation in response to the stratification of water column respectively, during the sapropel deposition. The average chain length of long-chain fatty acids records the regional vegetation changes in the Mediterranean borderlands and plausibly indicates the response of vegetation on the shift of Inter-Tropical Convergence Zone and variation in the North African monsoonal intensity. Various elemental abundances document a complex interplay of oceanographic and hydrological conditions during this period. For example, Br abundances indicate increased productivity during sapropel deposition, while K, Ti and Zr indicate variations in drainage and dust intensity.

The CCaT proxy derived sea surface temperature and average chain length of long- chain fatty acids show prominent multi-decadal oscillations during this period. Similar oscillations in elemental data (for Ca, Fe, Ti and K) highlight a coupling between low and mid-latitude hydrodynamic changes and teleconnections between various components of the global climate system during the last interglacial.