GEOTRACES Pacific Meridional Transect: Measurement of chlorofluorocarbons and sulfur hexafluoride

国际GEOTRACES项目的目标是了解海洋中微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GEOTRACES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面的海洋深度考察。本项目的目的是测量沿这一监测站样带的氯氟化碳化合物和六氟化硫的浓度。这些气体测量可以用来确定水体的“年龄”以及重要的海洋和生物地球化学过程的速率。这些信息对于解释将作为GEOTRACES的一部分收集的微量元素和同位素数据至关重要。痕量气体浓度、通风年龄和速率数据将在收集后的6个月内提供给其他研究人员，为GEOTRACES太平洋项目奠定重要基础。项目团队将测量2018年太平洋经向样带上的CFC-11、CFC-12和SF6浓度。除了浓度测量之外，该项目还有以下具体目标：1)计算示踪剂年龄，并确定不同环流体系中微量元素及其同位素（TEIs）所在的温跃层和中间水团的相对通风和稀释程度；2)计算生化重要过程的速率（包括表观氧利用率和反硝化速率），并区分不同环流体系中物理和生物地球化学过程的贡献；3)使用历史示踪剂、水文、ARGO CTD和氧气数据，将示踪剂和水文GEOTRACES数据置于更大的空间和时间尺度的背景下。CFC和SF6示踪剂数据将通过表征影响微量元素形态和内部循环的物理过程，有助于解释关键的GEOTRACES微量元素和同位素。计算示踪剂年龄是该项目的支柱，也是其他GEOTRACES pi的主要服务。示踪剂年龄将用于解决每个目标。由于示踪剂年龄是GEOTRACES项目的重要组成部分，因此将估算与海洋内部变率和大气瞬变的非平稳性引起的混合效应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.