Collaborative Research: US GEOTRACES GP17-OCE: Understanding neodymium isotopes and rare earth element systematics in the South Pacific

国际GEOTRACES计划的目标是了解海洋中多种化学元素及其同位素的分布。美国国家科学基金会正在支持美国在南太平洋和南大洋进行的一次地理轨迹采样考察，南太平洋和南大洋是地球上最偏远、采样最少的海洋地区之一。钕(ND)同位素和稀土元素(REE)是用于跟踪全球环流路径上的水团、追踪大陆输入海洋的来源以及限制水柱中的生物地球化学过程的重要工具。在这次考察中，研究人员将分析海水、悬浮颗粒和岩心顶部沉积物中的ND同位素和稀土元素。该项目将支持一名职业生涯早期的首席研究员、两名博士后研究人员和几名本科生。GP17-OCE巡航轨道经过精心设计，以阐明支配稀土和钕同位素海洋循环的过程，因为它(1)覆盖了营养稀少的南太平洋环流，(2)穿越亚热带、亚南极和极地锋面，捕捉到不同生产力制度之间的过渡，(3)穿越高纬度南太平洋，那里有广泛的深水上升流和新的水团形成。它提供了一个独特的机会，以前所未有的详细程度研究南太平洋具有重要生物地球化学意义但基本上未采样的区域。研究人员计划(1)产生海水ND同位素和REE数据，以表征在高纬度南太平洋形成的中、深水团；(2)破译跨大洋锋面和大气尘埃通量梯度的溶解ND同位素和REE丰度的演化；(3)确定颗粒丰度、组成和大小在调节溶解的ND同位素和REE中的作用；(4)评估南极和智利边缘的REE贡献对水柱ND同位素和REE库存的影响；(5)评估REE海底通量的影响，(6)了解深水与沉积档案(鱼牙化石、铁锰氧化物涂层)之间的信号传递过程。这些信息对于我们理解ND在全球海洋中的循环很重要，也将有助于对作为过去水循环代理人的ND同位素的使用进行彻底评估。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of the international GEOTRACES program is to understand the distributions of multiple chemical elements and their isotopes in the oceans. The National Science Foundation is supporting a U.S. GEOTRACES sampling expedition in the South Pacific and Southern Ocean, one of the most remote and poorly sampled ocean regions on Earth. Neodymium (Nd) isotopes and rare earth elements (REE) are important tools used to track water masses along global circulation pathways, trace the sources of continental inputs into the oceans, and constrain biogeochemical processes in the water column. The investigators will analyze Nd isotopes and REE in seawater, suspended particles, and core top sediments on this expedition. The project will support an early career lead investigator, two postdoctoral researchers, and several undergraduate students. Outreach to local high schools and paid undergraduate research positions are designed to broaden participation in geosciences.The GP17-OCE cruise track is well-designed for illuminating the processes that govern the marine cycling of REE and Nd isotopes, as it (i) covers the oligotrophic South Pacific Gyre, (ii) crosses the sub-tropical, sub-Antarctic and polar fronts, capturing transitions between different productivity regimes, (iii) traverses through the high latitude South Pacific, which hosts areas with extensive deep water upwelling and new water mass formation. It offers a unique opportunity to study biogeochemically important yet largely unsampled regions in the South Pacific at unprecedented detail. The investigators plan to (1) generate seawater Nd isotope and REE data to characterize the intermediate and deep water masses that form in the high latitude South Pacific, (2) decipher the evolution of dissolved Nd isotope and REE abundances across oceanic fronts and atmospheric dust flux gradients, (3) identify the roles of particle abundance, composition, and size in modulating dissolved Nd isotopes and REE, (4) evaluate the effect of REE contributions from the Antarctic and Chilean margins on water column Nd isotopes and REE inventory, (5) evaluate the impacts of the benthic flux of REE, (6) understand the process of signal transfer between the deep water and sedimentary archives (fossil fish teeth, Fe-Mn oxide coatings). This information is important for our understanding of Nd cycling in the global ocean and will also facilitate a thorough evaluation of the use of Nd isotopes as a past water circulation proxy.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.