Carbonate chemistry and other variables observed during RV METEOR cruise M187 (ReSEAt) from Walvis Bay, Namibia to Walvis Bay, Namibia@en

Carbonate chemistry parameters (pH, total alkalinity [TA], and partial pressure of CO₂ [pCO₂]) along with other oceanographic variables (temperature, salinity, nitrate [NO₃⁻], chlorophyll a [Chl a], and dissolved oxygen [DO]) were measured during the RV METEOR cruise M187 (ReSEAt; 25 January – 2 March 2023; Walvis Bay, Namibia – Walvis Bay, Namibia) using a suite of sensors . Surface water measurements of TA, pCO₂ and pH were obtained using an in situ total alkalinity analyzer (ISA-TA) with a ~7-minute sampling interval, a pCO₂ sensor (HydroC, 4H-Jena Engineering GmbH, Germany) with a 1-minute interval and a pH sensor (Sunburst Sensors, USA) with a 15-minute interval, respectively. All sensors (ISA-TA, pCO₂, pH, and nitrate) were installed in a 68 L tank positioned on a laboratory sink, which was continuously supplied with underway surface seawater (from a depth of ~5 m) during filament tracking. The water flow rate into the tank was maintained at approximately 30 L/min, enabling rapid turnover and ensuring near-real-time measurement of changing water properties. Sensor deployment and data acquisition followed established protocols as described in Qiu et al. (2023a, 2023b, 2024), Fietzek P., et al. (2014) and Nehir M., et al. (2021). We defined the relative coordinates of each cross-filament section (1 to 12), with –1 and +1 representing the southern and northern boundaries (distance normalized), respectively. These boundaries were determined based on the maximum density gradient on each side. Subsequently, all data were interpolated onto a uniform grid ranging from -6 to 6 with a spacing interval of 0.01. Chl a and dissolved oxygen values were provided by a PocketFerryBox system.本数据集涵盖碳酸盐化学参数（pH、总碱度（total alkalinity [TA]）与二氧化碳分压（partial pressure of CO₂ [pCO₂]））及其他海洋学变量（温度、盐度、硝酸盐（nitrate [NO₃⁻]）、叶绿素a（chlorophyll a [Chl a]）与溶解氧（dissolved oxygen [DO]）），数据采集于RV METEOR（流星号科考船）航次M187（ReSEAt；2023年1月25日—3月2日；纳米比亚瓦维斯湾—纳米比亚瓦维斯湾），通过成套传感器完成原位观测。其中，表层海水的TA、pCO₂及pH数据分别通过原位总碱度分析仪（ISA-TA，采样间隔约7分钟）、pCO₂传感器（德国4H-Jena工程有限公司HydroC型，采样间隔1分钟）及pH传感器（美国Sunburst Sensors公司产品，采样间隔15分钟）获取。所有传感器（ISA-TA、pCO₂、pH及硝酸盐传感器）均安装于一个安置在实验室水槽内的68升储水箱中。在丝状体追踪过程中，该水箱持续接入取自约5米深度的走航表层海水，水箱进水流速维持在约30升/分钟，可实现水体快速更新，确保水质变化的近实时监测。传感器部署与数据采集遵循邱等（2023a、2023b、2024）、菲策克P.等（2014）及内希尔M.等（2021）已确立的规范流程。本研究定义了每个跨丝截面（编号1至12）的相对坐标，其中-1与+1分别代表南、北边界（距离已归一化），上述边界依据截面两侧的最大密度梯度确定。随后，所有数据均被插值至范围为-6至6、间隔为0.01的均匀网格中。叶绿素a与溶解氧数据由PocketFerryBox观测系统提供。