Primordial Helium and Vertical Mixing at the Midatlantic Ridge, 2°S-11°S

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Typical hydrothermal fluids have ³He concentrations several orders of magnitude higher than the oceanic background. Because ³He has such a high concentration in the hydrothermal vent fluids, ³He can be used to trace hydrothermal plumes for thousands of kilometers from the source regions. So far, no hydrothermal vent fields have been identified in the South Atlantic. There are however strong indications from ³He measurements in the water column that several hydrothermal vents exit at the Mid-Atlantic ridge (Rüth et al., 2000). We propose to (1) To generate the three - dimensional primodial ³He distribution above the MAR in the SPP research region between 4°S and 11°S and to estimate the output of primordial helium from the resarch area. (2) To estimate the geothermal output. (3) To estimate the strengh of the vertical mixing above the MAR in dependence of the roughness of the topography. (4) To calculate stratification anomalies, three-dimensional velocity fields and turbulent mixing near and above hydrothermal vents. The proposed work contributes to the SPP theme: energy and material transport from the mantle to the ocean.