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

This data was collected in October 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1213R0.Departed: Hobart, Australia, October 23, 2012Arrived:      Dumont d'Urville station, Antarctica, October 28, 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海洋学院（IMOS）机遇船舶走航CO₂测量研究小组，于2012年10月采集自“L'Astrolabe”号科考船（IMOS平台代码：FHZI）的AL1213R0航次。
本航次起航信息：2012年10月23日从澳大利亚霍巴特出发；抵达信息：2012年10月28日抵达南极迪蒙·迪维尔站。

CO₂系统概述：表层海水二氧化碳逸度（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）进行测定。具体流程为：将海水喷入平衡舱，顶空气体中的二氧化碳与海水达到气液平衡；随后顶空气体依次流经热电冷凝器、纳菲恩干燥管，再进入Licor 7000型非分散红外气体分析仪，以测定干燥空气中的二氧化碳摩尔分数（XCO₂）。二氧化碳测定过程中会暂时中断气流，且所有测定均在大气压条件下完成。每间隔约3小时，会分析一组覆盖海洋环境预期CO₂浓度范围的4种CO₂标准气体（见表1），用于对气体分析仪进行校准。完成标准气体校准后，通过船舶前部桅杆上的进气口抽取洁净外界空气，以此测定大气干燥态XCO₂。

海水取水口位于船艏约3米水深位置，取水口处安装有远程温度传感器（Seabird Electronics SBE38），用于测定海表温度（sea surface temperature, SST）；在取水口附近的首侧推舱内，安装有热盐计（Seabird Electronics SBE21），用于测定海表盐度。从取水口到CO₂分析系统的输水时长通常约50秒，过程中水温升高幅度一般小于0.4℃。热盐计的供水同样取自该取水口及配套输水管道。

本数据集的气象数据、盐度、海表温度、船舶位置与时间均取自船舶日志系统。研究人员将SBE21测定的盐度值，与本航次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、船舶位置与时间均取自船舶日志系统。