IMOS - Ships of Opportunity - Ocean Carbon Dioxide Data from RV Aurora Australis voyage AA1112V6 (Hobart-Hobart)

This data was collected in April/May2012 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on RV Aurora Australis (IMOS platform code: VNAA) voyage AA1112V5.Departed:     Hobart, Tasmania, April 16, 2012Arrived: Hobart, Tasmania, May 01, 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）船舶走航CO₂测量研究小组于2012年4—5月，搭载“极光南极号”科考船（RV Aurora Australis，IMOS平台编号：VNAA）执行AA1112V5航次期间采集。本航次于2012年4月16日从塔斯马尼亚州霍巴特港启航，同年5月1日返回霍巴特港。

二氧化碳系统概况：
采用通用海洋科学公司（General Oceanics Inc.）的自动化测量系统（型号8050；参照Pierrot等人2009年的研究），测定表层海水二氧化碳逸度分压（fCO₂）。具体流程为：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。随后将顶空气体依次通入热电冷凝器（thermoelectric condenser）、纳菲恩干燥管（nafion drying tube），再流经Licor 7000型非分散红外气体分析仪，以测定干燥空气的CO₂摩尔分数（XCO₂）。CO₂测量环节会临时中断气流，测量在大气压条件下完成。每约3小时分析一组覆盖海洋典型CO₂浓度范围的4种标准CO₂气体，用于校准气体分析仪。完成标准气体校准后，通过船舶前桅的进气口抽取清洁室外空气，测定大气干燥态XCO₂。

海水采样与辅助数据：
海水采样点位于水下约6米深度。采样点处安装了海鸟电子（Seabird Electronics）SBE38型远程温度传感器，用于测定海表温度（SST）。海表盐度通过安装在pCO₂分析系统旁海洋学实验室中的海鸟电子SBE21型温盐仪测定。采样点至CO₂分析系统的输水时长通常约70秒，在接近冰点的冷水域中，输水过程中水温升高通常小于0.7℃。温盐仪的供水同样取自该采样点及输水管道。

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。