IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from MV L'Astrolabe voyage AL1112R4 (Hobart-Dumont d'Urville station)

This data was collected in February 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1112R4.Departed: Hobart Australia, February 19, 2012Arrived:      Dumont d'Urville station, Antarctica, February 25, 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.

本数据集由综合海洋观测系统（Integrated Marine Observing System，IMOS）机遇船舶走航二氧化碳测量研究组，于2012年2月搭乘L'Astrolabe号科考船（MV L'Astrolabe，IMOS平台代码：FHZI）执行航次AL1112R4期间采集。
起航：澳大利亚霍巴特，2012年2月19日
抵达：南极迪蒙·迪维尔站，2012年2月25日

## 二氧化碳系统概述
表层海水二氧化碳逸度（fugacity of carbon dioxide, fCO₂）采用General Oceanics公司自动化系统（型号8050；Pierrot等，2009）进行测定。具体流程为：将海水喷入平衡腔室，使顶空气体（headspace gas）中的二氧化碳与海水实现气液平衡；随后将顶空气体泵送至热电冷凝器（thermoelectric condenser），经纳菲恩干燥管（nafion drying tube）脱水后，通入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（CO₂ mole fraction, XCO₂）。测量二氧化碳时需暂时切断气流，所有测定均在大气压下完成。
每约3小时分析一组覆盖海洋典型二氧化碳浓度范围的4种二氧化碳标准气体（详见表1），用于校准气体分析仪。完成标准气体校准后，通过船舶前桅处的进气口抽取清洁外界空气，以测定干燥大气中的XCO₂。

海水采样口设置于船舶船首约3米水深处。采样口处安装有SeaBird Electronics SBE38型远程温度传感器，用于测定海表温度（sea surface temperature, SST）；海表盐度则采用安装在采样口附近船首侧推舱内的SeaBird Electronics SBE21型走航温盐仪（thermosalinograph）进行测定。从采样口至二氧化碳分析系统的输水时长通常约为50秒，输水过程中海水升温幅度通常不超过0.4℃，且走航温盐仪的采样水源与二氧化碳分析系统取自同一采样口及输水管道。

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。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。