CRUISE REPORT: Benguela Air-Sea CO2 and Heat Flux Experiment (Benflex)

The ocean plays a vital role in regulating atmospheric carbon dioxide. Roughly, 23% of anthropogenic carbon dioxide emissions have been taken up the ocean in the past six decades (Engelbrecht and Monteiro, 2021). Accurate estimates of air-sea carbon dioxide flux are crucial to forecast climate change, to predict and quantify potential effects of changes in the chemistry of sea water on marine ecosystems, and in developing mitigation measures. The Benguela Air-Sea CO₂ and Heat Flux Experiment (Benflex21) was initially planned to take place onboard the SA Agulhas II polar research ship but for technical reasons, that was not possible. The experiment was then replanned to take place in the southern Benguela Upwelling System (sBUS) on a long-term observational line in St Helena Bay (Fig 1). 

The aims of the experiment were to examine, through top-down eddy co-variance and bottom-up in situ ocean observations, the hypothesis that small differences between the skin, foundation, and bulk temperatures are causing an underestimation of the air-sea flux of CO₂ that can influence the magnitude of the global ocean sink (Watson et al., 2020; 1992; Woolf et al., 2017).