US GEOTRACES GP17-OCE: Mass balance constraints on in situ and ex situ drivers of open ocean iodine cycling and paleo proxy applications

US GEOTRACES GP17-OCE：公海碘循环和古代理应用的原位和异位驱动因素的质量平衡约束

• 批准号: 2147905
• 负责人: Dalton Hardisty
• 金额: $ 33.25万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2147905&HistoricalAwards=false
• 关键词: US; GEOTRACES; GP17; OCE; Mass

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. This project would add a study of iodine cycling to a U.S. GEOTRACES expedition to the South Pacific and Southern Ocean. Iodine geochemistry is widely applied as a tracer of oxygen availability and carbon cycling in ancient seawater and is a key regulator of tropospheric ozone. However, fundamental constraints on the role of local biogeochemical versus regional physical mixing processes in governing large-scale distribution of iodine (in the form of iodide and iodate species) in the ocean are lacking. This study would be the first investigation aimed at constraining the relative impact of these important processes on iodine across an ocean basin. The project would support graduate and undergraduate students. The lead investigator and the graduate student would participate in science communication activities to Greater Lansing K-12 students through the Michigan State University Museum.This project proposes to utilize the GEOTRACES GP17-OCE meridional Pacific transect from Tahiti to Chile to conduct the first basin-scale mass balance of iodine, quantifying biogeochemical and physical mixing processes governing iodine cycling evolution across key gradients. Specific objectives include: (A) determine the relative contributions of vertical mixing and productivity and nutrient variations toward maintaining euphotic, meridional iodine speciation gradients; (B) budget the roles of water mass mixing and iodine redox transformations during the downwelling and circulation of high latitude near-surface water masses, most prominently the Antarctic Intermediate Water. The two proposed mass balance studies include iodine speciation measurements from vertical profiles along targeted intervals of the transect and computational constraints on water mass abundances via an Optimum Multi-Parameter Analysis. Importantly, the project is uniquely poised for success because the GP17-OCE transect captures gradients in and already prioritizes tracers for vertical/horizontal mixing and water mass age. Together, these parameters will place first order constraints on the role of primary production in driving iodine redox transformations in oxic, euphotic waters and quantify rates of change across the proposed basin-scale spatiotemporal gradients associated with biogeochemical and physical mixing mechanisms.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.

国际地学研究计划的目标是了解海洋中痕量化学元素及其同位素的分布。该项目将把一项关于碘循环的研究添加到美国地理追踪公司对南太平洋和南大洋的考察中。碘地球化学在古代海水中被广泛用作氧有效性和碳循环的示踪剂，是对流层臭氧的关键调节因子。然而，缺乏对地方生物地球化学与区域物理混合过程在管理海洋中大规模分布碘(以碘化物和碘酸盐物种的形式)方面的作用的根本制约。这项研究将是第一次旨在限制这些重要过程对整个海洋盆地碘的相对影响的调查。该项目将支持研究生和本科生。首席研究员和研究生将通过密歇根州立大学博物馆参加与大兰辛K-12学生的科学交流活动。该项目提议利用从塔希提岛到智利的GEOTRACES GP17-OCE子午线太平洋样带进行第一次盆地规模的碘质量平衡，量化控制关键梯度上碘循环演变的生物地球化学和物理混合过程。具体目标包括：(A)确定垂直混合、生产力和营养变化对维持经向真光碘形态梯度的相对贡献；(B)估算水团混合和碘氧化还原转化在高纬度近地表水团--最突出的是南极中层水--下流和循环过程中的作用。两项拟议的质量平衡研究包括沿样带目标区间的垂直剖面的碘形态测量，以及通过最佳多参数分析对水团丰度的计算限制。重要的是，该项目是独一无二的成功准备，因为GP17-OCE样带捕捉到了坡度，并已经优先考虑垂直/水平混合和水团年龄的示踪剂。总而言之，这些参数将对初级生产在含氧、真光水体中驱动碘氧化还原转化的作用施加一级约束，并量化与生物地球化学和物理混合机制相关的拟议盆地尺度时空梯度的变化率。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。