SGER: Determining Equatorial Upwelling Rates with a Novel Geochemical Tracer Technique

在探索项目中，研究人员建议开发一种新的同位素技术，以同位素铍7为基础，推断赤道上升流的速率。铍7的样本将于2009年4月在美国国家科学基金会资助的东大西洋赤道研究巡航中收集。巡航轨道是理想的研究建议。远离赤道的几个站点将被占用，在冷舌地区的上升流区域内进行大量的混合层测量和铍7的几个剖面，主要集中在5°E和10°W之间的区域。铍7剖面将与CTD站同时收集，使用由研究人员开发的成熟技术。要验证的关键假设是，观察到的混合层铍7浓度是上涌速率的一个极其敏感的指标。铍7的两个性质使它成为研究上升流的理想示踪剂。首先，它的源函数和水柱分布（混合层和亚混合层深度的高度对比）使其成为上升流的敏感指标。其次，它的特征时间尺度足够长，可以在数周内整合上升流，但仍然对季节性时间尺度的变化很敏感，这与半衰期明显较长的示踪剂不同。更广泛的影响。上升流是影响全球海洋气候动力学和生物地球化学循环的重要物理过程。上升流的直接测量是困难的，因为所涉及的速度相对较小，因此必须通过间接方法推断，例如通过示踪观测提供的方法。如果成功，这种方法将为海洋学界提供一个重要的示踪工具。研究结果将被纳入共同研究者教授的本科和研究生课程。

In the exploratory project, the investigators propose to develop a novel isotopic technique, based on the isotope Beryllium 7, to infer rates of upwelling along the equator. Beryllium 7 samples will be collected on an NSF-funded research cruise to the equatorial eastern Atlantic in April, 2009. The cruise track is ideal for the proposed study. Several stations away from the equator will be occupied to make numerous mixed layer measurements and several profiles of Beryllium 7 within the areas of upwelling in the cold tongue region, focusing primarily on the region between 5°E and 10°W. The Beryllium 7 profiles will be collected simultaneously with the CTD stations using well established techniques developed by the investigators. The key hypothesis to be tested is the idea that the observed mixed layer Beryllium 7 concentration is an extremely sensitive indicator of the upwelling rate. Two properties of Beryllium 7 make it an ideal tracer for investigation of upwelling. First, its source function and water column distribution (high contrast between mixed layer and sub-mixed layer depth) allow it to be a sensitive indicator of upwelling. Secondly, its characteristic time scale is long enough to integrate upwelling over periods of weeks but still be sensitive to variations on seasonal timescales, unlike tracers with significantly longer half-lives.Broader Impacts. Upwelling is an important physical process affecting climate dynamics and biogeochemical cycling within the global ocean. Direct measurements of upwelling are difficult because of the relatively small velocities involved, and it must therefore be inferred by indirect methods such as those provided by tracer observations. If successful, this method will provide an important tracer tool to the oceanographic community. The findings will be incorporated into undergraduate and graduate courses that the co-investigator teaches.