IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from RV Aurora Australis voyage AA1213V1 (Hobart-Hobart)

This data was collected in November - December 2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on RV Aurora Australis (IMOS platform code: VNAA) voyage AA1213V1.Departed:     Hobart, Tasmania, November 19, 2012Arrived: Hobart, Tasmania, December 14, 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.

本数据集由海洋综合观测系统（Integrated Marine Observing System，IMOS）的船舶走航在线CO₂测量研究组，于2012年11—12月期间，在“极光南极号”（RV Aurora Australis，IMOS平台代码：VNAA）的AA1213V1航次中采集。
本航次于2012年11月19日从塔斯马尼亚州霍巴特港启航，2012年12月14日返回该港。

CO₂系统概况：
表层海水二氧化碳逸度（fugacity of carbon dioxide, fCO₂）采用General Oceanics Inc.生产的自动化系统（型号8050；参考Pierrot等2009年研究）进行测定。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。随后将顶空气体依次经热电冷凝器、纳菲隆干燥管输送，再通过Licor 7000型非分散红外气体分析仪，以测量干燥空气中的CO₂摩尔分数（XCO₂）。测量过程中会临时暂停气流，且所有测定均在大气压条件下开展。每约3小时，会使用一套覆盖海洋预期CO₂浓度范围的4种CO₂标准气体对气体分析仪进行校准。完成标准气体校准后，通过船舶前桅的进气口抽取外部洁净空气，以测定大气干燥态XCO₂。

海水采样及辅助数据：
海水采样点设于约6米水深处。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）。毗邻pCO₂系统的海洋学实验室内，搭载了海鸟电子SBE21型热盐仪（thermosalinograph），用于测定海表盐度。海水从采样点输送至CO₂系统的传输时长通常约为70秒，在接近冰点的冷水域中，水温升高幅度通常不超过0.7℃。热盐仪的供水同样取自该采样点及同一输水管道。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。