GEOTRACES Atlantic Section: Measurement of Helium Isotopes and Tritium

这笔快速反应研究赠款(RAPID)将为伍兹霍尔海洋研究所的一个研究小组提供资金，以继续他们在中断的GEOTRACES北大西洋分区段收集氚和氦同位素样品的工作，最初是由NSF ARRA奖资助的。由于科考船Knorr推进系统的机械故障，原巡航行程缩短了约三分之一，科考队的大部分人被迫在佛得角群岛下船。需要额外的努力来翻新采样船，并为2011年10月举行的第二次邮轮重新进行采样工作。该研究小组将进行氦同位素和氚测量，为在美国第一个GeoTraces全球勘探区继续进行的更重要的TEI测量提供有用的生物地球化学率信息。氚和~3He测量对该计划的主要贡献包括：(1)量化MOC中的过境时间尺度和TEI稀释：~H和~3He是确定深西部边界洋流示踪剂传输速率和内部混合稀释尺度的有用示踪剂，这对许多TE I来说是一个重要问题。(2)作为浅水计时器：使用氚-3He时钟，我们可以确定从6个月到几十年的时间尺度上流体块被消减以来所经过的时间。我们还可以结合~3H-3He年龄和演化的~3He分布与地转、T、S、O_2、养分和TEI分布来估计转化率。(3)TEI温跃层回流计：3He是一种独特的营养型？一种瞬时示踪剂，可用作所谓的通量计，以确定温跃层重新矿化的TEI返回上层海洋的速率。这对生物地球化学模型很重要。(4)测量热液稀释标度：在热液活动期间注入的火山3He是这些羽流中稀释作用的强有力的保守示踪剂，可以诊断一些热液活动的非保守行为，并允许估计与盆地和全球尺度上的热液活动有关的通量。P.I.将负责氚和3He的获取、测量、解释和建模，以实现上述目标。更广泛的影响：拟议的工作是为了支持GEOTRACES计划，因为这有助于该计划所支持的更广泛的社会目标和智力目标。与此相关的主要问题涉及了解碳循环和预测/减缓气候变化，以及海洋食物网和人类对海洋的影响。

This Grant for Rapid Response Research (RAPID) will provide funding to a research team at the Woods Hole Oceanographic Institution to continue their collection of tritium and helium isotope samples on the interrupted GEOTRACES North Atlantic Zonal Section originally funded through an NSF ARRA award. Due to the mechanical failure of the research vessel KNORR's propulsion system, the original cruise was cut short about one third of the way through, and most of the scientific party was obliged to disembark in Cape Verde Islands. Extra effort is required to refurbish sampling vessels and re-stage the sampling effort for the second cruise set for October, 2011. The research team will make helium isotope and tritium measurements to provide useful biogeochemical rate information for the more centrally important TEI measurements made on the continuation of the first U.S. GEOTRACES global survey section. The primary contributions that tritium and 3He measurements can make to the program include: (1) Quantifying transit timescales and TEI dilution in the MOC: 3H and 3He are useful tracers for determining deep western boundary current tracer transport rates and interior mixing dilution scales, an important issue for many TEIs.(2) As a shallow water chronometer: using the tritium-3He clock, we can determine the time elapsed since fluid parcels have been subducted on timescales ranging from 6 months to several decades. We can also combine 3H - 3He ages and evolving 3H and 3He distributions with geostrophy, T,S, O2, nutrient, and TEI distributions to estimate transformation rates. (3) A TEI thermocline reflux gauge: 3He e is a unique ?nutrient-like? transient tracer that can be used as a so-called flux gauge to determine the rates at which thermocline-remineralized TEIs are returned to the upper ocean. This is important for biogeochemical models. (4) Gauging TEI hydrothermal dilution scales: Volcanic 3He injected during hydrothermal activity is a powerful conservative tracer of dilution in these plumes, allowing diagnosis of non-conservative behavior in some TEIs, and permitting flux estimates associated with hydrothermal activity on basin and global scale. The P.I. will be responsible for the acquisition, measurement, interpretation and modeling of the tritium and 3He to achieve the above objectives. Broader Impacts: The proposed work is in support of the GEOTRACES program, as such contributes to the broader societal goals and intellectual objectives espoused by that program. The primary issues related to this are pertinent to understanding the carbon cycle and predicting/mitigating climate change, as well as the marine food web and anthropogenic impacts on the oceans.