| Summary: | 14th International Conference on Paleoceanography, 29 August - 2 September 2022, Bergen The Mediterranean Sea currently represents one of the most vulnerable climate change hotspots due to, among other factors, its relatively small basin size, restricted water exchange connections, and much shorter turnover time than the global oceans. These characteristics make it also especially vulnerable to ocean acidification resulting from the drastic anthropogenic increase in atmospheric CO2 since the Industrial Revolution. Indeed, instrumental measurements confirm the seawater acidification trend in this basin, not only at surface but in the whole water column. Reconstructing paleo-pH in the Mediterranean Sea is therefore relevant to understand the evolution of the carbon system and to project future changes in ocean chemistry and climate. The boron isotopic composition (d11B) of foraminiferal shells allows the reconstruction of seawater pH over time. In this work, we are carrying out d11B analysis on planktonic and benthic foraminifera from Mediterranean Sea sediment cores. Sample cleaning, preparation, chemical purification, and isotopic analyses are being performed at the University of Barcelona. For this, we have set up the methodology, including the purification of boron from the foraminifera carbonate matrix using microsublimation, as well as the d11B analysis using a Nu Plasma 3 Multi Collector Inductively Coupled Plasma Mass Spectrometer (MC-ICPMS). We are focusing on a series of sediment cores from the Strait of Sicily, which are allowing us to develop pH reconstructions over different timescales and temporal resolutions: from the last centuries to glacial/interglacial cycles. Preliminary results point towards an acidification trend during the last century, correlated with the anthropogenically induced rise in atmospheric CO2, and also to pH decreases associated to glacial/interglacial transitions Peer reviewed
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