Abstract The Southern Ocean today is a globally relevant sink for atmospheric carbon dioxide (), where the biological uptake of carbon through primary productivity is largely controlled by widespread iron (Fe) limitation. We analyze observations from a submesoscale‐resolving cross‐section of the Antarctic Circumpolar Current (ACC) obtained around one thousand kilometers downstream of South Georgia in the Atlantic sector during austral spring 2022. Vertically integrated chlorophyll peaked in a strong (250 mgChl‐a m −2 ) phytoplankton bloom within the central portion of the jet associated with the Southern ACC Front. We infer that winds drove a northward Ekman transport of dense water across the front and that this destabilized the water column, leading to an Ekman Buoyancy Flux (EBF) and enhanced vertical mixing ( −2 m 2 s −1 ) across the base of the mixed layer. Using in situ measurements of dissolved iron, we estimate a net flux to the bloom of up to 3 molFe m −2 d ‒1 from a subsurface pool. This large flux can supply the same amount of Fe per unit area in one day as that supplied to the upstream Georgia Basin bloom through deep wintertime entrainment in 1 year. We calculate the bloom's daily Fe demand from in situ 55 Fe uptake measurements by phytoplankton and find it to be of a similar order of magnitude as the EBF‐driven supply. We conclude that the bloom's strength and compact latitudinal extent are explained by EBF. Thus, EBF represents a previously understudied mechanism, which contributes to bloom patchiness and modulates biologically mediated drawdown in the iron‐limited Southern Ocean. Plain Language Summary The Southern Ocean absorbs a significant amount of atmospheric carbon dioxide, but its productivity is often limited by iron availability. In this study, we analyzed data from a high‐resolution survey across a number of strong oceanic fronts downstream of South Georgia during spring 2022 in the South Atlantic. We found a strong phytoplankton bloom where eastward winds pushed dense water across the fronts, creating instability, which increased mixing between the surface and deeper, iron‐rich water. This resulted in a supply of iron to the bloom, which supported the bloom's intense growth. Our findings suggest that this wind‐driven mixing is a key, previously overlooked process that shapes phytoplankton blooms and influences uptake of carbon dioxide in the Southern Ocean. Key Points Wind‐driven Ekman buoyancy flux (EBF) enhanced mixing at the base of the mixed layer and drove an iron supply to the surface of the Southern Ocean The iron supply supported an intense phytoplankton bloom 1,000 km downstream of South Georgia in the early growing season EBF influences bloom heterogeneity and modulates the biological carbon sink in the Southern Ocean