Exploring the Southern Ocean overturning circulation pathways in its tri-dimensions, and its link to the global ocean carbon sink – EXCITING

New analytical approaches will be developed and applied to diverse observations and model simulations to address one major issue facing climate science: “How do regional asymmetries in the Southern Ocean shape the tri-dimensional structure of the overturning circulation and how does this circulation impact on Southern carbon uptake and sequestration?” The large-­scale overturning circulation traverses the world’s oceans, distributing tracers such as carbon around the globe, and drives the storage of carbon in the oceans. The oceans slow down the rate of climate change by absorbing about 25% of the annual CO2 emissions due to human activities. 40% of the global oceanic anthropogenic CO2 enters the ocean via the Southern Ocean.

The Southern Ocean naturally lends itself to interpretations using a zonally averaged framework and most, if not all, overturning studies have been tackled in this context. Yet, recent studies have suggested the importance of regional asymmetries for the Southern Ocean
dynamics. However, the processes involved and their impact on the overturning are still not clear. I propose here an ambitious project at the crossroad of experimental and numerical oceanography, as well as physical and biogeochemical oceanography, extracting the best of each to explore the regional pathways of the overturning circulation, which are keystones for our climate but are, as yet, uncharted. This implies several fundamental issues ranging from process studies to climate impact, and via investigation of regional overturning routes.

EXCITING attacks directly those issues by proposing a series of scientific breakthroughs, including (i) an innovative combination of existing observation datasets to investigate surface-­to-­interior ocean mass flux, (ii) a state-of-the-art inverse model development to chart regional overturning routes, and (iii) a study of ocean interior anthropogenic carbon pathways. Altogether, the project will contribute to a new insight into climate feedbacks to future changes.