GEOTRACES Pacific Meridional Transect: Measurement of chlorofluorocarbons and sulfur hexafluoride

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。美国国家科学基金会正在支持2018年在太平洋进行的美国地理轨迹采样考察，该考察将在从阿拉斯加向南延伸到塔希提岛的地点进行全海洋深度测量。该项目的目的是测量该样带站点沿线的氯氟烃(CFC)化合物和六氟化硫(SF6)浓度。这些气体测量可以用来确定水团的“年龄”，以及重要的海洋和生物地球化学过程的速率。这类信息对于解释将作为地球空间观测系统一部分收集的微量元素和同位素数据至关重要。示踪气体浓度、通风年龄和速率数据都将在收集后六个月内提供给其他调查人员，这是GEOTRACES太平洋计划的重要基础。项目团队将在2018年太平洋子午线断面上测量CFC-11、CFC-12和SF6的浓度。除浓度测量外，该项目还有以下具体目标：1)计算示踪剂年龄，确定温跃层和中间水团的通风和稀释的相对程度，其中微量元素及其同位素存在于不同的循环系统中；2)计算具有生物化学重要性的过程的速率(包括表观氧利用率和反硝化率)，区分不同循环系统的物理和生物地球化学过程的贡献；3)利用历史示踪剂、水文学、ARGO CTD和氧数据，将示踪剂和水文地理信息系统数据纳入更大的空间和时间尺度。氯氟化碳和六氟化硫示踪剂数据将通过描述可能影响痕量元素形态形成和内部循环的物理过程，帮助解释地球物理系统的关键痕量元素和同位素。计算的示踪年龄是该项目的支柱，也是其他GEOTRACES PI的主要服务。将使用示踪剂年龄来解决每个目标。由于示踪年龄是GEOTRACES计划贡献的一个重要部分，将估计与海洋内部变化和大气瞬变非平稳混合影响有关的年龄的不确定性。

The goal of the international GEOTRACES program is to understand the distributions of trace chemical elements and their isotopes in the oceans. The National Science Foundation is supporting a U.S. GEOTRACES sampling expedition in the Pacific Ocean in 2018, that will conduct full ocean depth at sites extending south from Alaska to Tahiti. The purpose of this project is to measure the concentrations of chlorofluorocarbon (CFC) compounds and of sulfur hexafluoride (SF6) along this transect of stations. These gas measurements can be used to determine the "ages" of water parcels and the rates of important oceanographic and biogeochemical processes. Such information is essential to the interpretation of the trace element and isotope data that will be gathered as part of GEOTRACES. The trace gas concentrations, ventilation ages, and rate data will all be made available to other investigators within six months of collection, forming an important foundation for the GEOTRACES Pacific program.The project team will measure CFC-11, CFC-12, and SF6 concentrations aboard the 2018 Pacific Meridional Transect. Beyond the concentration measurements, the project has the following specific objectives: 1) Calculate tracer ages and identify the relative extent of ventilation and dilution of thermocline and intermediate water masses within which Trace Elements and their Isotopes (TEIs) reside across different circulation regimes, 2) Calculate rates of biochemically important processes (including apparent oxygen utilization and denitrification rates) and distinguish between the contributions from physical and biogeochemical processes across the different circulation regimes, 3) Put tracer and hydrographic GEOTRACES data into context of larger space and time scales using historical tracer, hydrographic, ARGO CTD and oxygen data. The CFC and SF6 tracer data will contribute to interpretation of the key GEOTRACES trace elements and isotopes by characterizing physical processes, which can affect trace element speciation and internal cycling. Calculated tracer ages are the backbone of this project and are the primary service for other GEOTRACES PIs. Tracer ages will be used to address each of the objectives. As tracer ages are an important part of the contribution to the GEOTRACES program, uncertainties will be estimated for the ages related to internal ocean variability and effects of mixing due to non-stationarity of the atmospheric transients.