Topography controlled mixing along mid-ocean ridges
Final Report Abstract
In this project, we examined hydrographic (stratification and current) as well as helium data for their potential to study vertical mixing and horizontal advection above mid-ocean ridges. Helium is a non-reactive noble gas, where the isotopic ratio 3He/4 He of mid-ocean hydrothermal fluids is enriched relative to atmospheric helium, and typical hydrothermal fluids have δ3He concentrations several orders of magnitude higher than the oceanic background. Because of these properties, helium is often used for tracing hydrothermal plumes over distances from a few hundred meters up to thousands of kilometers from the source regions. Here, we have found that the distribution of the primordial helium is also a proxy for the strength of vertical mixing processes that spread the signal from its source in the axial valleys of mid ocean ridges higher up into the water column. It can also be used to identify barriers in the horizontal advection of water bodies, which makes it a useful tool in biogeography to study the dispersal of vent species and connectivity on larger scales.
