IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from MV L'Astrolabe voyage AL1112R0 (Dumont d'Urville station - Hobart)

This data was collected in December 2011 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1112R0.Departed: Dumont d'Urville station, Antarctica, December, 2011Arrived: Hobart Australia, December 12, 2011Data was collected from 6th-10th of December.CO2 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IMOS机会船舶走航CO₂测量研究组，于2011年12月搭乘MV L'Astrolabe号（IMOS平台代码：FHZI）执行航次AL1112R0期间采集。本次航次起航于南极迪蒙·迪维尔站，起航时间为2011年12月；抵达澳大利亚霍巴特港，抵达时间为2011年12月12日；数据采集时段为2011年12月6日至10日。

CO₂系统概况：表层海水二氧化碳逸度（fCO₂）采用General Oceanics Inc.自动化测量系统（型号8050；Pierrot等，2009）进行测定。具体流程为：将海水喷入平衡腔，使顶空气体中的CO₂与海水达到气液平衡。随后将顶空气体泵送至热电冷凝器，经纳菲昂干燥管除湿后，流经Licor 7000型非分散红外气体分析仪，以测定干燥空气中的CO₂摩尔分数（XCO₂）。CO₂测量过程中会暂时中断气流，且测量在大气压条件下完成。

每间隔约3小时，将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），以完成气体分析仪的校准。完成标准气体校准后，通过船舶前桅杆的进气口抽取外部洁净空气，测定大气干燥XCO₂。

海水取水口位于船舶船艏约3米水深处，取水口处安装有Seabird Electronics SBE38型远程温度传感器，用于测定海表温度（Sea Surface Temperature, SST）。船艏侧推舱靠近取水口处安装了Seabird Electronics SBE21型热盐深仪，用于测量海表盐度。取水口至CO₂分析系统的海水输送时长通常约为50秒，期间海水升温幅度一般小于0.4℃。热盐深仪的取水同样取自该取水口及配套供水管路。

气象数据、盐度、海表温度、船舶位置及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水样，对SBE21型热盐深仪测得的盐度值进行了交叉校准验证。