Paper: Reconciling atmospheric CO2, weathering, and calcite compensation depth across the Cenozoic
Featured image: Figure 1 from a related study: Boudreau et al., 2018 – a schematic which illustrates the carbonate/calcite compensation depth (CCD). Just as snow accumulates on mountains above the snowline and melts at lower elevations, white calcium carbonate shells and minerals (the sinking green discs in this image) accumulate on the seafloor above the CCD and dissolve below this depth.
Authors: Nemanja Komar and Richard E. Zeebe
For multiple decades, we have known that temperatures have largely cooled over the last 66 million years (during the Cenozoic, our current geological era). This insight comes from measuring oxygen isotopes in microfossil shells from ocean sediment cores that extend hundreds of meters into the deep ocean seafloor. Slight increases in the heavier oxygen isotope (which contains ten neutrons) relative to the lighter isotope (which contains eight neutrons) in these shells over time indicates cooling. However, it has been significantly more difficult to understand how the long-term geological carbon cycle has been intertwined with this temperature change. Since carbon and climate are inherently connected under modern and projected future climate change, it is crucial to understand these linkages. A new study by Komar and Zeebe expands a multi-faceted geological carbon and climate model to show how geological and geochemical evidence from ocean sediments that initially appears to be incompatible actually tells a cohesive story of carbon cycling and changes over the Cenozoic.
Continue reading “Cohesive trends in carbon cycling over the last 66 million years”