Thursday 24 February, 4 PM CET
DR. ANNA NELE MECKLER
ABSTRACT: The evolution of deep-sea temperatures as extracted from the oxygen isotope composition of benthic foraminifera has been used as benchmark time series for global temperature across the Cenozoic. However, the oxygen isotope signal reflects the combined influence of changes in temperature and seawater isotopic composition. Previous attempts at independent reconstruction of ocean temperature with Mg/Ca ratios have similarly been hampered by changes in the composition of seawater with time. Clumped isotope thermometry, based on isotope ordering within molecules, now opens new possibilities for independently reconstructing ocean temperatures. We have been using this technique to revisit the Cenozoic history of deep ocean temperature in the North Atlantic, leading to some surprising results. We find a similar general cooling trend as seen in oxygen isotope and Mg/Ca records, but overall warmer temperatures compared to these previous reconstructions. In addition, our data suggest previously unrecognized large temperature swings lasting several million years under late Paleocene to early Eocene (~58-48 Ma) greenhouse conditions.