Carbon pathways in the Southern Ocean

ended

The Biological Carbon Pump (BCP) transfers atmospheric CO2, fixed by phytoplankton in the sun-lit upper ocean, as particulate organic carbon to the deep ocean. The BCP plays a key role in Earth’s climate by removing 10 Pg of carbon from surface waters each year, with the Southern Ocean (SO) pump representing 33% of the global BCP. Carbon export from the BCP has long been solely attributed to the gravitational sinking of large particles following the spring phytoplankton bloom. Conspicuous imbalances in ocean carbon budgets have recently challenged this long-lived paradigm. Several lines of observational evidence have demonstrated the importance of additional export pathways that transfer all classes of particles to depth at different times of the year. Physical transport of organic matter by vertical mixing or active transport by zooplankton vertical migration should now be considered as major components of the BCP. CAPTURE (CArbon PaThways in the soUtheRn ocEan) aims at developing a mechanistic and quantitative understanding of these BCP components using year-round and depth-resolved observations from heavily instrumented Biogeochemical Argo floats. We will address the interlinking of these components over complete annual cycles, introducing the novel concept of BCP seasonality. This multidisciplinary approach, combining physical oceanography, phytoplankton and zooplankton ecology and biogeochemistry, will fundamentally change our understanding of key climate-related processes and help close ocean carbon budgets. By providing a synoptic vision of the biogeochemical state of the SO and its capacity to store atmospheric CO2, CAPTURE will address a major societal challenge and assist decision-makers. The transfer of knowledge between all partners of this project, from both academic and industrial sectors, will enhance European scientific excellence and career prospects of the applicant.