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

在探索性项目中，研究人员建议开发一种新的同位素技术，以同位素BER17为基础，推断沿着赤道的上升流速率。2009年4月，由国家科学基金会资助的一次前往赤道东大西洋的研究巡航将收集BERG7样本。巡航跟踪是拟议研究的理想选择。将占用远离赤道的几个站进行大量的混合层测量，并在冷舌区的上升流区域内进行Berlove7的几个剖面测量，主要集中在5°E和10°W之间的区域。将使用调查人员开发的成熟技术，与CTD台站同时收集Berbert7剖面。待检验的关键假设是，观测到的混合层Berlene 7浓度是上涌速率的一个极其敏感的指标。BERGINE7的两个性质使其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（混合层和次混合层深度之间的高对比度）使其成为上升流的敏感指标。其次，其特征时间尺度足够长，可以将数周的上升流综合起来，但仍然对季节时间尺度的变化敏感，不像示踪剂的半衰期要长得多。上升流是影响全球海洋气候动力学和海洋地球化学循环的重要物理过程。直接测量上升流是困难的，因为所涉及的速度相对较小，因此，它必须推断的间接方法，如示踪观测提供的。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。研究结果将纳入合作研究者教授的本科生和研究生课程。

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.