National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2022

Storms drive outgassing of CO2 in the subpolar Southern Ocean

Nicholson, S.-A., D.B. Whitt, I. Fer, M.D. Du Plessis, A.D. Lebéhot, S. Swart, A.J. Sutton, and P.M.S. Monteiro

Nature Commun., 13, 158, doi: 10.1038/s41467-021-27780-w, View online (open access) (2022)

The subpolar Southern Ocean is a critical region where CO2 outgassing influences the global mean air-sea CO2 flux (FCO2). However, the processes controlling the outgassing remain elusive. We show, using a multi-glider dataset combining FCO2 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 FCO2 but also the effects of synoptic variability on slower seasonal or longer ocean physics-carbon dynamics.

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