Deep Ocean Experiments with Fossil Fuel Carbon Dioxide:
Creation and Sensing of a Controlled Plume at 4 km Depth

Peter G. Brewer,1 Edward T. Peltzer,1 Peter Walz,1 Izuo Aya,2 Kenji Yamane,2
Ryuji Kojima,2 Yasuharu Nakajima,3 Noriko Nakayama,1,4 Peter Haugan5 and Truls Johannessen5

1: Monterey Bay Aquarium Research Institute, Moss Landing, California, 95039 U.S.A.
2: Osaka Branch, National Maritime Research Institute, 3-5-10 Amanogahara, Katano, Osaka 576-0034, Japan.
3: Main Branch, National Maritime Research Inst. (NMRI), 6-38-1 Sinkawa, Mitaka, Tokyo 181-0004, Japan.
4: Ocean Research Institute, University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo 168-8639, Japan.
5: University of Bergen, Allegaten 70, N-5007 Bergen, Norway.

Journal of Marine Research (2005) 63: 9–33.

Received: 2004 July 12.
Revised: 2005 February 2.


ABSTRACT

The rapidly rising levels of atmospheric and oceanic CO2 from the burning of fossil fuels has lead to well-established international concerns over dangerous anthropogenic interference with climate. Disposal of captured fossil fuel CO2 either underground, or in the deep ocean, has been suggested as one means of ameliorating this problem. While the basic thermodynamic properties of both CO2 and seawater are well known, the problem of interaction of the two fluids in motion to create a plume of high CO2/low pH seawater has been modeled, but not tested. We describe here a novel experiment designed to initiate study of this problem. We constructed a small flume, which was deployed on the sea floor at 4 km depth by a remotely operated vehicle, and filled with liquid CO2. Seawater flow was forced across the surface by means of a controllable thruster. Obtaining quantitative data on the plume created proved to be challenging. We observed and sensed the interface and boundary layers, the formation of a solid hydrate, and the low pH/high CO2 plume created, with both pH and conductivity sensors placed downstream. Local disequilibrium in the CO2 system components was observed due to the finite hydration reaction rate, so that the pH sensors closest to the source only detected a fraction of the CO2 emitted. The free CO2 molecules were detected through the decrease in conductivity observed, and the disequilibrium was confirmed through trapping a sample in a flow cell and observing an unusually rapid drop in pH to an equilibrium value.

© 2005 by Journal of Marine Research.


Acknowledgements

This paper is in acknowledgment of the extraordinary influence of Nick Fofonoff on ocean science. Nick was a distinguished presence at the Woods Hole Oceanographic Institution throughout the 24 years that the first author of this paper worked there. It was Nick’s early work on the thermodynamic properties of seawater that drew attention, and it was Nick that sponsored the work of Alvin Bradshaw on the simple, accurate, and elegant measurement of these properties. From Nick’s kindly suggestion sprung a multi-year collaboration between Brewer and Bradshaw, with publication of a 1975 paper in this journal on chemical perturbations to the conductivity-density-salinity relationship that is still cited today. Thank you, Nick. We also thank two anonymous reviewers for their significant help in revising the manuscript.

This work was made possible by the skilled contributions of the pilots of the ROV Tiburon, and the captain and crew of the RV Western Flyer. Financial support was provided by the David and Lucile Packard Foundation, by an international research grant from the New Energy and Industrial Technology Organization (NEDO), Japan, and by the U.S. DoE/NETL Ocean Carbon Sequestration Program (Grants No. DE-FC26-00NT40929 and DE-FC03-01ER6305).


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