The role of mesoscale eddies in Southern Ocean Carbon fluxes from autonomous ocean gliders

The Southern Ocean (SO) is thought to account for the uptake of ~40% of all global human-derived (anthropogenic) carbon dioxide and >75% of anthropogenic heat, thus being disproportionately influential in the ongoing mitigation of increasing atmospheric CO2 levels and related climate effects. SO CO2 fluxes are a delicate balance of multiple processes; temperature-driven solubility effects, biological carbon drawdown driven by vertical nutrient supply, upwelling-derived outgassing of remineralised carbon, sea-ice formation and melt, and circulation features such as large-scale overturning or mesoscale eddies together combine to make flux estimates difficult and highly uncertain. Our understanding of their present state and future behaviour are limited by both spatial and temporal sparsity of observations, and the inability of models to replicate them, particularly circulation-driven biological effects. Recently, biogeochemical floats (sampling the water column's top 2000m every 10 days) have massively increased data coverage and led to new flux estimates suggesting a much smaller regional CO2 sink than previously thought. However, float sampling strategies are thought to be insufficient to capture the intensity of short-lived major flux events and features (such as eddies), and the variability of their occurrence, which may compromise their estimates. High frequency glider observations offer the opportunity to fill these gaps, thereby reconciling disparities between integrated observational budget estimates and biogeochemical models, and reducing uncertainties in flux estimates.