A multi-proxy approach to decipher global sea-level and ice-volume dynamics during late Cenozoic “snapshot” intervals based on benthic foraminiferal calcite from ODP Site 849

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The increasing influence of humans on Earth's climate causes global warming and hence melting of polar ice sheets and a rise in global sea levels. To protect coastal regions from rising seas in a warming future, accurate projection of future sea-level change is needed. Therefore, this project aims to better understand sea-level and ice-volume dynamics in a world that is warmer-than-today. For this purpose, sea-level/ice-volume change will be reconstructed for six critical glacial-interglacial cycles from the past 5 million years of Earth’s history (Marine Isotope Stages (MIS) 1–5, MIS 29–31, MIS 57–59, MIS 99–101, MIS M1–MG1, and MIS CN5–CN7). These late Cenozoic “snapshot” intervals yield decisively different background conditions in terms of global ice volume, but include phases that represent close analogues to a warming future with regard to orbital configuration, atmospheric greenhouse-gas concentration and/or temperature. The proposed study will be based on the geochemical analysis of well-preserved benthic foraminifera retrieved from a drill core in the Eastern Equatorial Pacific Ocean (Ocean Drilling Program Site 849). More precisely, oxygen-isotope analysis will be combined with Mg/Ca- and “clumped-isotope”-derived deep-sea temperatures to yield the oxygen-isotope composition of seawater, which is a proxy for global ice-volume and hence sea-level change. This multi-proxy approach includes two independent paleothermometers (Mg/Ca and “clumped isotopes”) to test the accuracy of the temperature signal extracted from oxygen isotopes to derive sea-level change. It therefore represents a critical step forward with respect to previous sea-level reconstruction techniques and will likely help to resolve inconsistencies in late Cenozoic sea-level records as they are yet available. Finally, records to be generated for the individual late Cenozoic “snapshot” intervals of this project will reveal both low-frequency (glacial-interglacial) sea-level/ice-volume changes, but also high-frequency variabilities connected to human-relevant timescales. The project will thus provide further clues to achieve a full mechanistic (glacial-interglacial to millennial-scale) understanding of global sea-level/ice-volume dynamics relevant within the overall context of near-future warming.