Fig. 3: Forward-tracking simulations from the Southeast Pacific Rise and coincident xs³He anomaly.

Trajectories of the forward-tracking simulations from the SEPR (A–C) and coincident xs³He anomaly (D). Trajectories were released between the ridge and 500 m above to mimic a neutrally buoyant hydrothermal plume. A Trajectory density, which indicates the number of instances of trajectories passing into a grid cell (log scale), of all SEPR trajectories. B Trajectory density map of SEPR trajectories that pass within a 0.5° area around the OOI station (red marker). C Depth section of trajectory density for the SEPR trajectories that pass within a 0.5° area of the OOI station (location indicated by pink line). Additionally, the grey line superimposed on the pink line highlights the depth range where dFe concentrations were >0.75 nM (Fig. 2). The cyan line marks the trajectory seeding depth which mimics a neutrally buoyant plume. Bathymetry along 54° S (to match station OOI) is shown. Note the colour bar scale is different for (C) compared to (A, B). D An east-west transect of excess Helium (xs³He) at 54° S as an indicator of hydrothermal influence from the Jenkins et al. dataset⁴⁹.