Control of Earth's climate(s) by the polar Southern Ocean

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How much heat and carbon will be taken up by the ocean in the future? This is one of the most pressing questions the scientific community must answer in order to help human society predict and adapt to global warming. On multidecadal to millennial time scales, the answer mostly lies in the polar (south of ~60S) Southern Ocean. Here, very dense water forms near the Antarctic coast and sinks to the abyss, driving the lower limb of the global overturning circulation and determining the ocean's ability to sequester heat and carbon in the abyss for centuries. However, a robust quantitative understanding of the mechanisms underpinning abyssal sequestration in the Southern Ocean is lacking, mainly due to the formidable challenges to the collection of measurements in this harsh and remote environment. The project aims to generate a state-of-the-art, baseline estimate of abyssal heat and carbon sequestration in the Southern Ocean, determining their controlling processes. To achieve this, I will combine recent in situ oceanographic data, satellite observations and stat-of-the-art modelling. The project will be carried out in the Department of Ocean and Earth Science at the University of Southampton, in collaboration with multiple national (the National Oceanography Centre and the University of Liverpool) and international (Scripps Institution of Oceanography, U.S., and CSIRO, Australia) institutes. This analysis will provide a new benchmark to test our current understanding of the Southern Ocean's role in the climate system and, if necessary, drive the emergence of a new paradigm. Given the Southern Ocean regulates climate on long time scales, this new knowledge will be used in the final years of the project to test (and possibly revisit) mechanisms of glacial-interglacial transitions and abrupt past climatic changes. I will combine idealized and climate models to better understand past climate transitions, opening the way for better predicting the long term (> 50 years) future of the Earth's climate system.