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

This data was collected in November 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on MV L'Astrolabe (IMOS platform code: FHZI) voyage AL1213R0.Departed: Dumont d'Urville station, Antarctica, November 17, 2012Arrived: Hobart Australia, November 22, 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IMOS机遇船舶走航CO₂测量研究团队于2012年11月在MV L'Astrolabe（IMOS平台代码：FHZI）的AL1213R0航次中采集。本次航次于2012年11月17日从南极洲迪蒙·迪尔维尔站（Dumont d'Urville station）启航，于2012年11月22日抵达澳大利亚霍巴特港。
CO₂系统概述：本研究采用通用海洋学公司（General Oceanics Inc.）8050型自动化系统（Pierrot等，2009），测量表层海水的二氧化碳逸度（fugacity of carbon dioxide, fCO₂）。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；顶空气体经热电冷凝器、纳菲恩干燥管后，通入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）。测量CO₂时会暂时中断气体流量，且所有测量均在大气压下进行。每约3小时便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），以此对气体分析仪进行校准。标准气体测量完成后，通过船舶前桅杆上的进气口抽取外部洁净空气，以测定大气干燥态CO₂摩尔分数（XCO₂）。
海水采样口位于船舶船首约3米水深处。采样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）；船首推进器舱内靠近采样口处安装了热盐仪（Seabird Electronics SBE21），用于测量海表盐度。从采样口到CO₂分析系统的输送时长通常约为50秒，期间海水升温通常不超过0.4℃，且热盐仪的供水同样取自该采样口及供水管路。
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。本次航次中，通过SBE21测得的盐度数据，与航次采集的离散采水器样本进行了比对校验。