The Mediterranean has great potential for reconstructing past climate due to high sedimentation rates and amplified climate signals. Recently, planktic foraminiferal δ18O records from the Mediterranean were used to reconstruct a 5.3 Myr sea-level record, the first millennially resolved reconstruction extending beyond 0.5 Myr which is independent from deep-sea benthic δ18O. However, the Mediterranean’s sedimentary record is punctuated by sapropels: periodic deep-sea anoxic events strongly associated with times of African monsoon intensification. The increased freshwater influx to the basin during sapropels decreases the δ18O of surface waters, creating anomalies in foraminiferal δ18O records which prevent robust interpretation of Mediterranean δ18O, and hence of palaeoclimatic reconstructions over these intervals. Despite extensive research on sapropels, the magnitude of monsoonal intensification and freshwater runoff, along with its influence on δ18O, remains elusive.
My PhD project was aimed at untangling the components of Mediterranean δ18O signals during these sapropel events, using a combination of proxy data collection and modelling. A multi-site, multi-species dataset of planktic foraminiferal δ18O was compiled for a case study of last interglacial sapropel S5 (~128-121 ka). The dataset was then used in conjunction with a model of the Mediterranean to deconvolve the δ18O records for sapropel S5. This work has enabled the first quantitative estimation of African monsoonal freshwater runoff during sapropel S5, and provided further insight to the system dynamics during these events.