Development of a Remote Analyzer of the CO2 System in Seawater Based on In Situ Measurement for pH and TCO2

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The Woods Hole Oceanographic Institution will undertake an ocean sciences instrumentation development project to develop, build and test an instrument to make autonomous in situ measurements of pH and Total carbon dioxide (TCO2)for extended periods from oceanographic moorings and remote platforms. The instrument will be designed to make measurements at frequencies less than (2/hr. Estimated unattended endurance will be about six months. Both components are based on existing laboratory methods. The pH measurements use well-developed spectrophotometric laboratory methods, while the TCO2 component utilizes exchange of CO2 across a semi-permeable membrane and detection of resulting conductivity changes in a dilute base. The objective is to achieve precision of ( (.002 pH units and (5 (mol/kg. To evaluate instrument performance, tests include short term wire deployments in the deep ocean, deployment on a benthic lander in the deep sea for 3 or 4 months, and near- surface deployment for approximately three months.