Explore the critical role of the Southern Ocean in glacial-interglacial climate cycles through this comprehensive AGU conference talk. Delve into the dynamic processes of the Southern Ocean and their impact on Earth's climate engine, including ocean-atmosphere CO2 partitioning, overturning circulation dynamics, winds, sea ice extent, and the biological pump. Examine recent insights on glacial CO2 sequestration in the deep ocean and outgassing across the last deglaciation, with a focus on oxygen isotope (δ18O) records in biogenic calcium carbonate. Learn about Cesare Emiliani's pioneering work using δ18O in foraminiferal fossils and the modern use of Emiliania huxelyi biomarkers for paleo-sea surface temperature reconstruction. Synthesize multiple proxies from across the Southern Ocean to understand its role in glaciation and deglaciation, and engage in the debate on whether the Southern Ocean was a driver or follower in these processes.