Investigations of Iron and Manganese Fluxes from Hydrothermal Sources in the South Atlantic Ocean



In recent decades the micronutrient iron has been shown to have a major role in controlling the key oceanic processes of primary productivity and nitrogen fixation. Yet our understanding of the major sources of iron to the oceans has been constrained by a severe lack of measurements, particularly in the deep ocean. Recently, we documented the presence of a large >1000km wide dissolved iron hydrothermal plume in the South Atlantic Ocean. While recent studies in the Pacific and Southern Oceans have found similar scale dissolved hydrothermal iron plumes, a recent modeling study does not predict a significant contribution of hydrothermal iron flux in the slow-spreading ridge basins, such as the South Atlantic Ocean. We propose to determine the extent of this South Atlantic hydrothermal iron plume through the collection of ~600 dissolved iron and manganese samples to create a full-depth meridional ocean section from 13oS to 33oS along the Southern Mid-Atlantic ridge on a German hydrothermal vent cruise. This study will help to constrain the importance of slow-spreading basins to the global oceanic iron inventory and allow improvements in global models.