CO2, Hydrographic, and Chemical Data Obtained During the R/V Hesperides Cruise in the Atlantic Ocean (WOCE Section A5, July 14 - August 15, 1992)

This data documentation discusses the procedures and methods used to measure total carbon dioxide (TCO2), total alkalinity (TALK), and pH at hydrographic stations during the R/V Hesperides oceanographic cruise in the Atlantic Ocean (Section A5). Conducted as part of the World Ocean Circulation Experiment (WOCE), the cruise began in Cadiz, Spain, on July 14, 1992, and ended in Miami, Florida, on August 15, 1992. Measurements made along WOCE Section A5 included CTD pressure, temperature, salinity, and oxygen; and bottle salinity, oxygen, phosphate, nitrate, nitrite, silicate, TCO2, TALK, and pH. The TALK, TCO2, and pH were determined from titrations of seawater collected at 33 stations. The titration systems for measuring TALK and TCO2 were calibrated in the laboratory with certified reference materials (CRMs) before the cruise to ensure that they gave reliable results for these parameters. Standard reference seawater provided by Andrew Dickson of Scripps Institution of Oceanography (SIO) was used at sea to monitor the performance of the titration systems. The results agree with the laboratory results to +/- 2 micro-mol/kg for TALK and +/- 1 micro-mol/kg for TCO2. The titration systems used to measure pH were calibrated with TRIS seawater buffers prepared in the laboratory and measured with an H2, Pt/AgCl, Ag electrode. The initial electromotive force (emf) of the titrations was used to determine the pH. The values of pH are thought to be reliable to +/- 0.01 and are internally consistent with the measured values of TALK and TCO2 to +/- 7 micro-mol/kg. The measured carbon dioxide system parameters have been used to calculate the in situ values of the fugacity of CO2 (fCO2) for the surface water. The surface results are briefly discussed. WOCE section A5 is located at 24.5 degrees N along the meridional overturn in the Atlantic Ocean. The maximum heat transfer in the North Atlantic Ocean occurs at 24 degrees north; warming in the ocean at this latitude goes down to 3000 m. This section has been studied for a number of years and thus can be used to examine the changes that have occurred in the North Atlantic deep waters. This section has also been studied in the past using inverse methods to look at the movement of CO2 to and from the North Atlantic. The WOCE Section A5 data set is available free of charge as a numeric data package (NDP) from the Carbon Dioxide Information Analysis Center. The NDP consists of two oceanographic data files, two FORTRAN 77 programs, a documentation file, and this printed report, which describes the contents and format of all files as well as the procedures and methods used to obtain the data. Instructions on how to access the data are provided.本数据文档详述了“赫西底斯号”（R/V Hesperides）海洋考察航次在大西洋A5断面水文站位处，总二氧化碳（total carbon dioxide, TCO₂）、总碱度（total alkalinity, TALK）与pH的测量流程与方法。本航次作为世界海洋环流实验（World Ocean Circulation Experiment, WOCE）的组成部分，于1992年7月14日从西班牙加的斯港启航，1992年8月15日于美国佛罗里达州迈阿密港结束。 WOCE A5断面的测量项目涵盖温盐深仪（CTD）测得的压力、温度、盐度与溶解氧，以及采水器水样的瓶测盐度、溶解氧、磷酸盐、硝酸盐、亚硝酸盐、硅酸盐、TCO₂、TALK与pH。其中TALK、TCO₂与pH的实测数据，来自33个站位采集的海水水样的滴定分析。 航次开展前，研究团队已在实验室使用标准参考物质（certified reference materials, CRMs）对TALK与TCO₂的滴定系统完成校准，以确保相关参数的测量结果可靠。航次执行期间，研究人员采用斯克里普斯海洋研究所（Scripps Institution of Oceanography, SIO）安德鲁·迪克森（Andrew Dickson）提供的标准参考海水，对滴定系统的运行性能进行监测。实测结果表明，TALK的测量不确定度控制在±2 μmol/kg以内，TCO₂的测量不确定度控制在±1 μmol/kg以内，与实验室校准结果一致性优异。 用于pH测量的滴定系统，以实验室自主配制的TRIS海水缓冲液完成校准，并通过H₂,Pt/AgCl,Ag电极完成电位测量。滴定初始的电动势（electromotive force, emf）被用于计算pH值。研究认为，该pH测量结果的不确定度可控制在±0.01以内，且与同期测得的TALK、TCO₂数据具有良好的内部一致性，偏差不超过±7 μmol/kg。 基于实测的二氧化碳系统参数，研究人员计算得到表层海水二氧化碳逸度（fugacity of CO₂, fCO₂）的原位值，并对表层测量结果进行了简要探讨。 WOCE A5断面位于大西洋经向翻转环流区域的24.5°N纬度处。北大西洋的最大热交换发生在24°N附近，该纬度带的海洋升温可延伸至3000米水深。该断面已被持续研究多年，可用于分析北大西洋深层水的长期变化情况。过往研究还通过反演方法，对北大西洋与全球大洋间的二氧化碳迁移过程开展了相关探讨。 本WOCE A5数据集可从二氧化碳信息分析中心（Carbon Dioxide Information Analysis Center）免费以数值数据包（numeric data package, NDP）形式获取。该数值数据包包含两份海洋学数据文件、两份FORTRAN 77程序代码、一份文档说明文件，以及本份详细阐述所有文件内容与格式、数据获取流程与方法的印刷报告。文档中同时提供了数据访问的具体操作指南。