Donald Penman, Ph.D.

My research focuses on the interplay between Earth’s climate and the geochemical cycing of carbon and other elements from the lithosphere into the atmosphere, ocean, and finally into sediments. As the oceans represent the largest surficial reservoir of carbon, characterizing the marine carbon cycle is crucial to understanding the long-term regulation of atmospheric pCO₂ and climate. With this goal in mind, I am trained in a suite of inorganic proxies for carbonate chemistry and climatic parameters preserved in geological archives, particularly deep-sea sediment cores. Due to the temporal coverage of sea-sediment records, my research has a Cenozoic focus. At UC Santa Cruz, my PhD thesis involved reconstructing the response of carbonate chemistry to rapid carbon release during the Paleocene-Eocene Thermal Maximum (PETM) on both short- and long-time scales. These new observations are used to guide carbon cycle modeling in order to constrain scenarios and mechanisms responsible for the PETM, as well as the processes involved in restoring equilibrium to the carbon cycle during the event’s recovery. The insights into the carbon cycle gleaned from my study of the PETM have assisted me as I expand my research areas to include other intervals of Earth history with the Hull and Planavsky research groups. Recent research has focused on the Middle Eocene Climatic Optimum (MECO), the Cretaceous-Paleogene exctinction, and Neoproterozoic “Snowball Earth” events.