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

典型的热液流体具有比海洋背景高几个数量级的He浓度。由于³He在热液喷口流体中具有如此高的浓度，他可以被用来追踪距离源区数千公里的热液羽流。到目前为止，在南大西洋还没有发现热液喷口。然而，从水柱的测量中有强烈的迹象表明，大西洋中部海脊存在几个热液喷口(Rüth等人，2000年)。我们建议(1)在4°S到11°S之间的SPP研究区产生MAR以上的三维原始氦分布，并估算研究区的原始氦产量。(2)地热产出量估算。(3)根据地形粗糙度估算MAR以上垂直混合强度。(4)计算热液喷口附近和上方的层结异常、三维速度场和湍流混合。拟议的工作对战略协作计划的主题作出了贡献：从地幔到海洋的能量和物质运输。

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.