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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L19313, doi:10.1029/2006GL027211, 2006

Entrainment and bending in a major hydrothermal plume, Main Endeavour Field, Juan de Fuca Ridge

Peter A. Rona

Department of Geological Sciences, Rutgers–State University of New Jersey, New Brunswick, New Jersey, USA

Karen G. Bemis

Department of Geological Sciences, Rutgers–State University of New Jersey, New Brunswick, New Jersey, USA

Christopher D. Jones

Applied Physics Laboratory, University of Washington, Seattle, Washington, USA

Darrell R. Jackson

Applied Physics Laboratory, University of Washington, Seattle, Washington, USA

Kyohiko Mitsuzawa

Japan Agency for Marine-Earth Science and Technology, Yokosuka, Japan

Deborah Silver

Department of Geological Sciences, Rutgers–State University of New Jersey, New Brunswick, New Jersey, USA

Abstract

We measure expansion rate and bending in a 23-hour time series of acoustic images of the lower 25 m section of a buoyant hydrothermal plume rising from Grotto vent in the Main Endeavour Field, Juan de Fuca Ridge. We then calculate entrainment coefficient, the constant of proportionality relating mean inflow velocity at the plume edge to maximum mean upward velocity within the plume. The plume section alternately bends southwest at relatively high inclinations (37°) and northeast at lower inclinations at irregular intervals twice during this time period, apparently driven by current reversals in the mixed semi-diurnal tidal cycle. The measured expansion rates (0.11–0.25 m/m) and calculated entrainment coefficients (0.07–0.18) are directly proportional to the degree of bending (R² = 0.75). The loss of buoyancy flux related to enhanced mixing in a stratified environment during bending may contribute to reduction of potential rise height consistent with predicted (∼400 m) and measured (300–350 m) plume tops.

Received 13 June 2006; accepted 31 August 2006; published 14 October 2006.

Index Terms: 3017 Marine Geology and Geophysics: Hydrothermal systems (0450, 1034, 3616, 4832, 8135, 8424); 4568 Oceanography: Physical: Turbulence, diffusion, and mixing processes (4490); 4832 Oceanography: Biological and Chemical: Hydrothermal systems (0450, 1034, 3017, 3616, 8135, 8424).

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Citation: Rona, P. A., K. G. Bemis, C. D. Jones, D. R. Jackson, K. Mitsuzawa, and D. Silver (2006), Entrainment and bending in a major hydrothermal plume, Main Endeavour Field, Juan de Fuca Ridge, Geophys. Res. Lett., 33, L19313, doi:10.1029/2006GL027211.

Copyright 2006 by the American Geophysical Union.