IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from MV L'Astrolabe voyage AL1112R2 (Hobart-Dumont d'Urville station)

This data was collected in January 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1112R2.Departed: Hobart Australia, January 06, 2012Arrived:      Dumont d'Urville station, Antarctica, January, 2012Data was collected from 7th-12th of January.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.

本数据集由澳大利亚海洋综合观测系统（Integrated Marine Observing System, IMOS）的"机遇船舶走航CO₂测量"研究小组，于2012年1月在MV L'Astrolabe（IMOS平台代码：FHZI）的AL1112R2航次中采集。
本航次于2012年1月6日从澳大利亚霍巴特起航，于2012年1月抵达南极迪蒙·迪维尔站，数据采集时段为1月7日至1月12日。

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.自动化系统（型号8050；参考Pierrot等2009年研究）进行测量。具体流程为：将海水喷入平衡舱，使顶空气体中的二氧化碳与海水达到气液平衡。随后顶空气体经热电冷凝器（thermoelectric condenser）、纳菲恩干燥管（nafion drying tube）除湿，再流经Licor 7000型非色散红外气体分析仪（non-dispersive infrared gas analyser），以测定干燥空气中的二氧化碳摩尔分数（XCO₂）。测量过程中会暂时中断气流，所有测量均在大气压下完成。每约3小时分析一组覆盖海洋预期CO₂浓度范围的4种CO₂标准物质（见表1），用于校准气体分析仪。完成标准物质校准后，通过船舶前桅杆的进气口抽取清洁外界空气，以此测定干燥态大气XCO₂。

海水取水系统相关参数：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）。船首侧推舱附近的取水口处搭载了热盐深仪（thermosalinograph），型号为Seabird Electronics SBE21，用于测量海表盐度。取水口至CO₂分析系统的水样传输时长通常约为50秒，传输过程中水温升温幅度通常小于0.4℃。热盐深仪的水样取自同一取水口及供水管路。

气象及辅助数据：气象数据、盐度、海表温度、船舶位置与时间信息均取自船舶日志系统。研究人员将SBE21测得的盐度值与本航次中采集的离散瓶采水样进行了比对校准。
气象数据、盐度、海表温度、船舶位置与时间信息均取自船舶日志系统。