IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from RV Aurora Australis voyage AA1112V4 (Fremantle-Hobart)

This data was collected in February/March 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on RV Aurora Australis (IMOS platform code: VNAA) voyage AA1112V4.Departed:     Fremantle, Western Australia, February 15, 2012Arrived: Hobart, Tasmania, March 15, 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 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. Seawater intake and ancillary data:The seawater intake is at about 6 m depth. 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 oceanographic lab next to the pCO2 system. The travel time between the intake and CO2 system is typically about 70 seconds with warming usually less than 0.7ºC in cold waters near freezing. 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.

本数据集由澳大利亚海洋综合观测系统（Integrated Marine Observing System, IMOS）的机会船舶走航CO₂测量研究小组，于2012年2月至3月在“极光南极号”（RV Aurora Australis，IMOS平台编号：VNAA）执行的AA1112V4航次中采集。
本航次于2012年2月15日从西澳大利亚州弗里曼特尔港启航，同年3月15日抵达塔斯马尼亚州霍巴特港。

CO₂系统概述：
表层海水二氧化碳逸度（fugacity of carbon dioxide, fCO₂）的测量采用通用海洋科学公司（General Oceanics Inc.）自动化测量系统（型号8050；Pierrot等，2009）。具体测量流程为：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（nafion）干燥管脱水后，通入Licor 7000型非色散红外气体分析仪，以测量干燥空气的CO₂摩尔分数（XCO₂）。CO₂测量环节将暂时中断气流，且全程在常压下进行。每约3小时即采用一套覆盖海洋典型CO₂浓度区间的4种标准CO₂气体对气体分析仪进行校准。完成标准气体校准后，通过船舶前桅杆的进气口抽取外部清洁空气，用以测量大气干燥态XCO₂。

海水采样及辅助数据：
海水采样点水深约6米。采样点处安装有海鸟电子（Seabird Electronics）SBE38型远程温度传感器，用于测量海表温度（sea surface temperature, SST）。海表盐度则通过安装在pCO₂系统旁海洋学实验室中的海鸟电子SBE21型热盐仪（thermosalinograph）进行监测。从采样点到CO₂测量系统的输水时长通常约70秒，在接近冰点的冷水域中，输水过程产生的水温升幅通常小于0.7℃。热盐仪的取水来源与CO₂测量系统一致，均取自同一采样点及输水管道。
气象数据、盐度、海表温度、船舶位置及时间信息均取自船舶自带的日志系统。