PhD Student Alex Reis will be sailing on IODP Leg 378- South Pacific Paleogene Climate and this project will constitute the majority of his dissertation

Pore water silicon and calcium isotopes in Southern Ocean and Australo-Antarctic Gulf sediments as evidence for changes in circulation and seawater chemistry

The opening of the Tasman Gateway and Drake Passage established the modern configuration of the Antarctic Circumpolar Current (ACC). The deepening of the Tasman Gateway (TG) has been well constrained to the Eocene-Oligocene transition from 35.5 to 30 Ma. As the warm, sub-tropical waters of the East Australian Current were replaced by the cold waters of the ACC during the opening of the TG, a transition from a silica-dominated system to a carbonate-dominated system is observed. This shift likely reflects changes in both productivity and sediment preservation. Variations in calcium and silicon isotopic ratios capture these changes, specifically providing a record of the dissolution history, as this system responded to fluctuations in climate over the past 30 million years. Examining how the system responds to these climatic events provides insight into how the ACC will respond to the effects of anthropogenic climate change in the future.