SO-CHIC Nicholson, SA., Whitt, D.B., Fer, I. et al. Storms drive outgassing of CO2 in the subpolar Southern Ocean. Nat Commun 13, 158 (2022)

January 10, 2022 Sarah-Anne Nicholson, Daniel B. Whitt, Ilker Fer, Marcel D. du Plessis, Alice D. Lebéhot, Sebastiaan Swart, Adrienne J. Sutton & Pedro M. S. Monteiro

The subpolar Southern Ocean is a critical region where CO₂ outgassing influences the global mean air-sea CO₂ flux (F_CO2). However, the processes controlling the outgassing remain elusive. We show, using a multi-glider dataset combining F_CO2 and ocean turbulence, that the air-sea gradient of CO₂ (∆pCO₂) is modulated by synoptic storm-driven ocean variability (20 µatm, 1–10 days) through two processes. Ekman transport explains 60% of the variability, and entrainment drives strong episodic CO₂ outgassing events of 2–4 mol m⁻² yr⁻¹. Extrapolation across the subpolar Southern Ocean using a process model shows how ocean fronts spatially modulate synoptic variability in ∆pCO₂ (6 µatm² average) and how spatial variations in stratification influence synoptic entrainment of deeper carbon into the mixed layer (3.5 mol m⁻² yr⁻¹ average). These results not only constrain aliased-driven uncertainties in F_CO2 but also the effects of synoptic variability on slower seasonal or longer ocean physics-carbon dynamics.

Publication DOI: https://doi.org/10.1038/s41467-021-27780-w