IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from MV L'Astrolabe voyage AL1213R0 (Dumont d'Urville station - Hobart)

This data was collected in November 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1213R0.Departed: Dumont d'Urville station, Antarctica, November 17, 2012Arrived: Hobart Australia, November 22, 2012CO2 System Overview:The fugacity of carbon dioxide (fCO2) in surface seawater was measured using a General Oceanics Inc. automated system (Model 8050; Pierrot et al 2009). Seawater is sprayed into an equilibration chamber and CO2 in the headspace gas equilibrates with the seawater. The headspace gas is pumped through a thermoelectric condenser followed by a nafion drying tube, before flowing through a Licor 7000 non-dispersive infrared gas analyser used to measure the CO2 mole fraction (XCO2) of the dried air. The gas flow is stopped temporarily for the CO2 measurements, which are made at atmospheric pressure. A set of four CO2 standards (Table 1) that cover the range of CO2 values expected in the ocean are analysed about every three hours to calibrate the gas analyser. Atmospheric XCO2 (dry) is measured after the standards by pumping clean outside air from an intake on the forward mast of the ship. The seawater intake is at about 3m depth in the bow of the ship. A remote temperature sensor (Seabird Electronics SBE38) located at the intake is used to measure sea surface temperature (SST). Sea surface salinity is measured using a thermosalinograph (Seabird Electronics SBE21) mounted in the bow thruster space near the intake. The travel time between the intake and CO2 system is typically about 50 seconds with warming usually less than 0.4ºC. The thermosalinograph water is from the same intake and supply line. Meteorological data, salinity, SST, and ships position and time are taken from the ship’s logging system. The salinity values measured by the SBE21 were checked against discrete bottle samples collected on the voyage.Meteorological data, salinity, SST, and ships position and time are taken from the ships logging system.

本数据集由澳大利亚综合海洋观测系统（Integrated Marine Observing System, IMOS）的“机遇船舶走航CO₂测量”研究小组，于2012年11月在MV L'Astrolabe（阿斯托拉贝号，IMOS平台代码：FHZI）的AL1213R0航次中采集。
航次概况：本次航次于2012年11月17日从南极洲迪蒙·迪维尔站起航，2012年11月22日抵达澳大利亚霍巴特港。
CO₂系统概述：表层海水二氧化碳分压（fugacity of carbon dioxide, fCO₂）采用General Oceanics Inc.公司的自动化测量系统（型号8050；参考Pierrot等2009年研究）完成检测。具体流程为：将海水喷入平衡舱，使顶空气体中的CO₂与海水充分平衡；随后将顶空气体泵送至热电冷凝器，经纳菲恩干燥管去除水汽后，流经Licor 7000型非分散红外气体分析仪，以测量干燥空气中的CO₂摩尔分数（XCO₂）。CO₂测量环节会暂时中断气流，所有测量均在大气压条件下完成。
每约3小时会分析一组覆盖海洋典型CO₂浓度范围的4种CO₂标准气体（详见表1），用于对气体分析仪进行校准。完成标准气体校准后，通过船舶前桅杆的进气口抽取清洁外界空气，以测量大气干燥XCO₂。
海水取水口位于船舶船首约3米水深处，取水口处安装有远程温度传感器（SeaBird Electronics SBE38），用于测量海表温度（Sea Surface Temperature, SST）；在靠近取水口的船首侧推舱内，安装了热盐深仪（SeaBird Electronics SBE21），用于测量海表盐度。取水口至CO₂测量系统的输水时长通常约为50秒，且输水过程中水温升高通常低于0.4℃。热盐深仪的取水水源与CO₂系统取自同一取水口及输水管道。
气象数据、盐度、海表温度以及船舶位置与时间信息均取自船舶日志系统。研究人员还通过本次航次采集的离散瓶采水样，对SBE21测量得到的盐度值进行了校准验证。