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

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: Dumont d'Urville station, Antarctica, January 23, 2012Arrived: Hobart Australia, January 30, 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）机遇船连续CO₂测量研究小组，于2012年1月通过MV“星盘号”（IMOS平台代码：FHZI）的AL1112R2航次采集。
该航次于2012年1月23日从南极洲迪蒙·迪尔维尔站起航，于2012年1月30日抵达澳大利亚霍巴特港。

## 二氧化碳系统概述
本研究采用通用海洋科学公司（General Oceanics Inc.）的自动测量系统（型号8050；Pierrot等，2009）测定表层海水二氧化碳逸度（fCO₂）。具体流程为：将海水喷入平衡舱，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，经纳菲恩干燥管除湿后，通入Licor 7000型非分散红外气体分析仪，测定干燥空气的CO₂摩尔分数（XCO₂）。
CO₂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小时便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），以此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清洁外界空气，以此测定大气干基XCO₂。
海水取水口位于船舶船首约3米水深处。取水口处安装的远程温度传感器（SeaBird Electronics SBE38）用于测定海表温度（SST）；海表盐度则通过安装在取水口附近船首推力舱内的船载流动式温盐仪（SeaBird Electronics SBE21）测得。
从取水口至CO₂分析系统的输水传输时间通常约为50秒，过程中水温升高一般不超过0.4℃。SBE21的取水样同样取自该取水口及供水管路。
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。SBE21测得的盐度值与本航次采集的离散瓶采水样进行了比对校准。