Constraining the Contribution of Hydrothermal Iron to Southern Ocean Export Production Using Deep Ocean Iron Observations

Hydrothermal iron supply contributes to the Southern Ocean carbon cycle via regulation of regional export production. However, as hydrothermal input estimates are coupled helium, which uncertain depending on whether helium inputs based ridge spreading rates or inverse modelling, questions remain regarding magnitude production impacts. A particular challenge is limited observations dissolved (dFe) from abyssal system directly assess different scenarios. We combine ocean biogeochemical modelling with new dFe impact estimated either rate The contribution in upper 250 m reduces 4–5 fold when relative those rate, translating into a 36–73% reduction only scheme reproduces observed anomalies >1 nM around circum-Antarctic ridge. model correlation drops 3 under scheme. best scenario has residence time for that between 21 and 34 years, highlighting importance rapid physical mixing surface waters. Overall, because its short time, Fe supplied locally by ridges most important our results highlight decoupling supply.