IMOS - SOOP Underway pCO2 System Overview

The CSIRO Ship of Opportunity Underway pCO2 system is mounted on the Research Vessel Southern Surveyor (IMOS platform code: VLHJ) of the Australian Marine National Facility.\r\n\r\nCO2 System Overview:\r\nThe fugacity of carbon dioxide (fCO2) in surface seawater is 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 that is 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 in-air standards that cover the range of CO2 values expected in the ocean are analysed about every four hours to calibrate the gas analyser. The standard gas concentrations are on the WMO-X2007 mole fraction scale for CO2-in-air. Atmospheric XCO2 (dry) is measured immediately after the standards by pumping clean outside air from an intake on the forward mast of the ship. \r\n\r\nSeawater intake and ancillary data:\r\nThe ships seawater intake is located at about 5.5m depth in the bow of the ship. Sea surface salinity is measured using a thermosalinograph (Seabird Electronics SBE21) located next to the CO2 system. A remote temperature sensor (Seabird Electronics SBE 38) located at the intake is used to measure sea surface temperature (SST). The travel time between the intake and CO2 system is typically about 4 minutes with warming usually less than 0.6ºC. The thermosalinograph water is from the same intake, but the supply lines separate after the intake. A comparison of thermosalinograph and equilibrator temperature records shows the temperature difference in the two lines is generally less than 0.1ºC. The thermosalinograph water line travels outside the ship and is typically warmer than the equilibrator. The travel time in water line to the thermosalinograph is 2.5 minutes faster than the equilibrator. \r\n\r\nMeteorological data, salinity, SST, and ships position and time are taken from the ships logging system. These parameters and the data quality are maintained by the Australian Marine National Facility.

澳大利亚联邦科学与工业研究组织（Commonwealth Scientific and Industrial Research Organisation, CSIRO）机遇航次走航式海水二氧化碳分压（underway pCO2）监测系统，搭载于澳大利亚海洋国家设施的"南方考察者号"研究船（IMOS平台代码：VLHJ）。

二氧化碳监测系统概览：
本系统采用General Oceanics公司的自动化监测系统（型号8050；Pierrot等，2009）测定表层海水二氧化碳分压（fugacity of carbon dioxide, fCO2）。具体流程为：将海水喷入平衡腔，使顶空气体中的二氧化碳与海水达到气液平衡。随后将顶空气体经热电冷凝器、纳菲恩（nafion）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二氧化碳摩尔分数（XCO2）。气体流速会在二氧化碳测定时段临时暂停，测定过程维持在大气压下。每间隔约4小时，会使用一组覆盖海洋环境中预期二氧化碳浓度范围的空气中二氧化碳标准气体校准气体分析仪，该标准气体浓度采用WMO-X2007空气中二氧化碳摩尔分数基准。完成标准气体校准后，会通过船首桅杆前方进气口抽取清洁外部空气，实时测定干燥大气中的XCO2。

海水采样与辅助数据：
该船的海水采样口位于船首约5.5米水深处。紧邻二氧化碳系统处安装了海鸟电子（Seabird Electronics）公司SBE21型热盐计（thermosalinograph），用于测定海表盐度；采样口处还部署了海鸟电子（Seabird Electronics）公司SBE 38型远程温度传感器，以监测海表温度（SST）。从采样口到二氧化碳系统的输水时长通常约为4分钟，且输水过程中水温升高通常小于0.6℃。热盐计的供水同样取自该采样口，但输水管道在采样口后即与二氧化碳系统管路分流。热盐计与平衡腔的温度记录对比显示，两条管路的水温差通常小于0.1℃。热盐计输水管道沿船外铺设，水温通常高于平衡腔管路。热盐计输水管道的输水时长比平衡腔管路短2.5分钟。

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，上述参数及数据质量均由澳大利亚海洋国家设施负责维护。