Surface Ocean Acidification studies using Ships Of Opportunity

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Ships of Opportunity

Ships of opportunity (SOOP) are used as a platform for cost-efficient collection of environmental data, Ferrybox. The SOOP network operated by NIVA cover the majority of the Norwegian coastline (from Germany (54N ) in the South to Svalbard (78N) in the North. This network is used in the national OA monitoring program. Globally, SOOPs are used for pCO2 measurements and this capacity will now be extended to the Norwegian coastline and Arctic Seas.

Ferrybox

Measurements of salinity, temperature, Chl a fluorescence, oxygen, cDOM, cyanobacteria and turbidity are collected autonomously and continuously with the Ferrybox system (Figure A). There are also optical and meteorological measurements on the deck for satellite validation. Water samples can be triggered remotely or manually and are stored in refrigerator until laboratory analyses. The data obtained are logged and can be seen both on-line or after processing, and are used in national and European monitoring programs. Data are transferred to MyOcean database.

Objectives

Ocean Acidification is a decrease of the seawater pH and has historically been measured from water samples using a time consuming process from fieldwork to laboratory analyses and calculations. A pair of the variables (AT, CT, pH or pCO2) can be used to calculate the marine carbonate system. New instruments for autonomous sampling of pCO2 and pH are being incorporated into the Ferrybox systems on all SOOPs operated by NIVA.

New Instuments for pCO2 AND pH

Membrane based pCO2 system (Franatech/NIVA) with solid state detector for continuous measurements of pCO2 (Figure B). Flow through system using Ferrybox pump, water leakage detector, internal logging and on-line software. Optional on-board calibration. A new miniature spectrophotometric detection system (NIVA) measures underway pH (Figure C). An internal pump draws water to a custom designed cuvette (provisional patent pending. USPTO), spectral absorbance processing after dye injection provides calibration free pH of the sample with precision < 10-3 pH, ±2.5x10-3 accuracy (2), drift within precision, max 2samples/min. Ongoing developments include the integration of a direct UV carbonate ions detection. Sensor developments are partly performed under the EU-Jerico project.

Conclusions

  • New instruments are under development that will give high resolution data on Ocean Acidification.
  • Standard Operation Procedure (SOP) should be made for membrane based systems of pCO2 detection (Providing a better understanding of humidity, pressure and temperature effects)
  • The pCO2 and pH data can be linked to parameters already obtained from the Ferrybox system; temperature, salinity, Chl a fluorescence, oxygen. Samples can also be obtained.

Acknowledgements

We acknowledge The Norwegian Climate and Pollution Agency (Klif) project on marine acidification, Fram center flagship on marine acidification and NIVAs strategic initiative on marine acidification. We acnowledge the collaboration with Michel Masson at Franatech, GmbH, for effort in the development of new instrumentation, and Tobias Steinhoff at GEOMAR for collaboration on sensor testing.

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