IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from RV Southern Surveyor voyage ST032009

This data was collected in October 2009 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on RV Southern Surveyor (IMOS platform code: VLHJ) voyage ST032009.Departed:     Hobart, Tasmania, October 10, 2009Arrived:     Sydney, New South Wales, October 14, 2009CO2 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 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 after the standards by pumping clean outside air from an intake on the forward mast of the ship. Seawater intake and ancillary data:The 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 to the equilibrator. Meteorological 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.

本数据集由澳大利亚海洋综合观测系统（Integrated Marine Observing System，简称IMOS）的“机会船走航CO₂测量”研究小组，于2009年10月搭乘“南方勘探者号”（RV Southern Surveyor，IMOS平台代码：VLHJ）执行航次ST032009期间采集。该航次于2009年10月10日从塔斯马尼亚州霍巴特起航，于2009年10月14日抵达新南威尔士州悉尼。

CO₂系统概况：本研究采用通用海洋科学公司（General Oceanics Inc.）生产的自动化测量系统（型号8050；参照Pierrot等，2009）测定表层海水二氧化碳逸度（fCO₂）。具体测量流程为：将表层海水喷入气液平衡舱，使顶空气体中的CO₂与海水达到热力学平衡；随后将顶空气体泵送至热电冷凝器，经纳菲隆（nafion）干燥管脱除水汽，再通过Licor 7000型非色散红外气体分析仪测定干燥空气中的CO₂摩尔分数（XCO₂）。CO₂浓度测量过程中会暂时中断气流，所有测量均在常压下完成。每间隔约4小时，即分析一组覆盖海洋典型CO₂浓度范围的4种标准CO₂气体，以完成气体分析仪的校准。标准气体的浓度采用WMO-X2007空气中CO₂摩尔分数标度。完成标准气体校准流程后，通过船舶前桅的进气口抽取洁净外界空气，以此测定大气干燥态XCO₂。

海水采样与辅助数据：海水采样口位于船舶船艏约5.5米水深处。CO₂测量系统旁搭载了Seabird Electronics SBE21型热盐计，用于测量海表盐度；采样口处安装有Seabird Electronics SBE 38型远程温度传感器，用于测定海表温度（SST）。从采样口到CO₂系统的输水耗时通常约4分钟，其间水体升温幅度一般不超过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CO₂系统的输水管道分流。对比热盐计与平衡舱的温度记录可知，两条输水管道的水温差通常小于0.1℃；热盐计输水管道沿船舶外部布设，其水温通常高于平衡舱输水管道。热盐计输水管道的输水耗时比平衡舱输水管道短2.5分钟。

气象数据、盐度、海表温度、船舶位置与时间数据均取自船舶日志系统。上述观测参数及对应数据质量均由澳大利亚海洋国家设施（Australian Marine National Facility）负责维护。