IMOS - SOOP Ocean Carbon Dioxide Data from RV Southern Surveyor voyage ST022009

This data was collected in July and August 2009 by the IMOS Ship of Opportunity Underway CO2 Measurement research group on RV Southern Surveyor (IMOS platform code: VLHJ) voyage ST022009.

Departed: Noumea, New Caledonia, July 29, 2009
Arrived: Hobart, Tasmania, August 6, 2009

CO2 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（IMOS, Integrated Marine Observing System）机会船舶走航CO₂测量研究小组，于2009年7月至8月在「南方考察者号（RV Southern Surveyor）」航次ST022009中采集，该航次的IMOS平台代号为VLHJ。

本航次于2009年7月29日从新喀里多尼亚努美阿起航，同年8月6日抵达塔斯马尼亚州霍巴特。

### CO₂系统概况
本研究采用通用海洋学公司（General Oceanics Inc.）的自动化系统（型号8050；参考Pierrot等，2009），测量表层海水二氧化碳分压（fCO₂）。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、纳菲恩干燥管（nafion drying tube），再通入Licor 7000型非色散红外气体分析仪，以测量干燥空气中的CO₂摩尔分数（XCO₂）。测量过程将临时暂停气流，且在大气压条件下完成。每间隔约4小时，会使用一套覆盖海洋环境预期CO₂浓度范围的4种CO₂标准气体对分析仪进行校准，该标准气体浓度基于WMO-X2007空气中CO₂摩尔分数尺度。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，以测量大气干燥态XCO₂。

### 海水采集与辅助数据
海水采样口位于船舶船首约5.5米水深处。CO₂系统旁配置了热盐深仪（thermosalinograph，Sea-Bird Electronics SBE21），用于测量海表盐度；采样口处安装有远程温度传感器（Sea-Bird Electronics SBE 38），用于获取海表温度（SST）。从采样口到CO₂系统的输水耗时通常约为4分钟，且输水过程中的水温升幅通常不超过0.6℃。热盐深仪的供水同样取自该采样口，但两条输水线路在采样口处分流。对比热盐深仪与平衡腔的温度记录可知，两条线路的温差通常小于0.1℃；由于热盐深仪的输水线路沿船体外部铺设，其水温通常高于平衡腔输水线路。热盐深仪的输水耗时比平衡腔输水线路快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，相关参数及数据质量由澳大利亚海洋国家设施（Australian Marine National Facility）负责维护。