Cenozoic evolution of deep ocean temperature from clumped isotope thermometry

Characterizing past climate states is crucial for understanding the future consequences of ongoing greenhouse gas emissions. Here, we revisit the benchmark time series for deep ocean temperature across the past 65 million years using clumped isotope thermometry. Our temperature estimates fromthe deep Atlantic Ocean are overall much warmer compared with oxygen isotope-based reconstructions, highlighting the likely influence of changes in deep ocean pH and/or seawater oxygen isotope composition on classical oxygen isotope records of the Cenozoic. In addition, our data reveal previously unrecognized large swings in deep ocean temperature during early Eocene acute greenhouse warmth. Our results call for a reassessment of the Cenozoic history of ocean temperatures to achieve a more accurate understanding of the nature of climatic responses to tectonic events and variable greenhouse forcing.

Automated summary

Characterizing past climate states is crucial for understanding the future consequences of ongoing greenhouse gas emissions. This study revisits the benchmark time series for deep ocean temperature across the past 65 million years and finds that the deep Atlantic Ocean was overall much warmer compared to previous reconstructions. The results also reveal previously unrecognized large swings in deep ocean temperature during the early Eocene period. This calls for a reassessment of the Cenozoic history of ocean temperatures to achieve a more accurate understanding of climatic responses to tectonic events and greenhouse forcing.