The Eocene-Oligocene Transition (EOT) marks a significant shift in Earth's climate from the warm conditions of the Eocene to the cooler, icehouse climate of the Oligocene, representing a pivotal environmental change during the Cenozoic era. Using full coupled Earth system models (CESM1.2), we find that the increase in dust after the EOT significantly contributed to the decline in global temperature, as well as the increase in ocean productivity and diatom biomass in the Southern Ocean. Firstly, dust can affect the Earth's radiation balance by directly scattering and absorbing solar radiation, leading to surface cooling. Second, the increased dust deposition post-EOT, which significantly impacted marine productivity and diatom abundance. The Southern Ocean received iron-rich dust, which  reduced the iron limitation on phytoplankton growth, particularly diatoms, a major contributor to carbon export to the deep ocean. Increased diatom productivity not only enhance the biological pump but also contribute to the long-term sequestration of carbon dioxide, thus reinforcing global cooling trends. Combining sediment cores and proxies for dust and ocean productivity, as well as reconstructed diatom records, this study quantitatively modeled the evolution of the earth system response to dust before and after the EOT. The results highlight the multifaceted role of dust in the Eocene-Oligocene climate transition. These findings contribute to a deeper understanding of the complex interactions between the atmosphere-land and the marine biosphere, highlighting the importance of dust in global climate and marine biogeochemical processes.

Eocene-Oligocene transition, dust, diatom, Antarctic glaciation