Three-dimensional acoustic monitoring and modeling
of a deep-sea CO2 droplet cloud

Peter G. Brewer,1 Baixin Chen,2 Robert Warzinski,3 Arthur Baggeroer,4
Edward T. Peltzer,1 Rachel M. Dunk,1 and Peter Walz1

1: Monterey Bay Aquarium Research Institute, Moss Landing, California, USA.
2: National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.
3: National Energy Technology Laboratory, U.S. Department of Energy, Pittsburgh, Pennsylvania, USA.
4: Department of Ocean and Electrical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

Geophysical Research Letters (2006) 33 L23607 doi:10.1029/2006GL027181.

Received: 2006 June 26.
Revised: 2006 August 7.
Accepted: 2006 October 20.
Published: 2006 December 8.


ABSTRACT

We show that release of 5 liters of liquid CO2 at 1000 m depth can be readily detected acoustically, and tracked for over 30 minutes, and 150 m of ascent, with both surface ship (38 kHz) and ROV (675  kHz) sonars. The released liquid broke up into droplets covered with a hydrate film. The remarkably sensitive acoustic response of the droplets may be attributed to the high sound speed contrast between CO2 (300 m/sec) and sea water (1500 m/sec), the near spherical shape of the droplets created by the hydrate shell, and the high compressibility of the liquid. The observed cloud conformed closely to models of CO2 disposal, allowing for reasonable predictions of larger scale processes. This offers a remarkably sensitive technique for examination in real time of engineered releases of CO2, volcanic sea floor liquid CO2 plumes, or leakage from geologic CO2 storage.

© 2006 by the American Geophysical Union.


Acknowledgements

We thank the pilots of the ROV Tiburon, and captain and crew of the R/V Western Flyer for expert help at sea. The work was supported by grants from the David and Lucile Packard Foundation (MBARI), and the U.S. Department of Energy. Baixin Chen was financially supported through the ARCS project, NETO, Japan.


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