Mantle helium reveals Southern Ocean hydrothermal venting

Hydrothermal venting along the global mid‐ocean ridge system plays a major role in cycling elements and energy between the Earth's interior and surface. We use the distribution of helium isotopes along an oceanic transect at 67°S to identify previously unobserved hydrothermal activity in the Pacific sector of the Southern Ocean. Combining the geochemical information provided by the helium isotope anomaly with independent hydrographic information from the Southern Ocean, we trace the source of the hydrothermal input to the Pacific Antarctic Ridge south of 55°S, one of the major global mid‐ocean ridge systems, which has until now been a ‘blank spot’ on the global map of hydrothermal venting. We identify three complete ridge segments, a portion of a fourth segment and two isolated locations on the Pacific Antarctic Ridge between 145°W and 175°W (representing ∼540 km of ridge in total) as the potential source of the newly observed plume.