Flow Over Ridges and Seamounts:

Model results from Gaia for motion at Axial Seamount. A) Mean flow is anti-cyclonic around the top of the volcano. B) The long-term mean thermal anomaly appears as a cold dome above and a warm apron below summit depth. (Click image for full-size.)

Flow Rectification at an Ocean Spreading Center

Problem Description:

The topography of mid-ocean ridge systems and seamounts increase the complexity of ocean currents. Those currents, in turn, advect hydrothermal geochemicals away from vent fields into the distal ocean. Current measurements at Juan de Fuca Ridge show that mean flow occurs in opposite direction each side of the ridge to normal distances of several tens of kilometers. Rectification of periodic flow is one possible causal mechanism. This study seeks to examine that possibility while laying the foundation for investigating along and off-axis transport of hydrothermal plumes.

a) Model isotherms evidence the effects of ridge-forced vertical motions. b) Model flow is northward along the ridge to the west and southward on the east when cross-axis flow is forced at weather time scales, in agreement with observations. c) A plan view snapshot of flow vectors at 2100 m shows enhanced flow at the ridge. click for larger view FLI Animation (1.2 mb) mov Animation (1.4 mb)

Related Papers:

Lavelle, J.W., E.T. Baker, and G.A. Cannon (2003): Ocean currents at Axial Volcano, a northeastern Pacific seamount. J. Geophys. Res., 108(C2), 10.1029/2002JC001305.

Lavelle, J.W. and G.A. Cannon (2001): On sub-inertial oscillations trapped by the Juan de Fuca Ridge, Northeast Pacific. J. Geophys. Res., 106(C12), 31,099-31,116.

Buoyant Plumes in Cross Flows

Cannon, G.A., and R.E. Thomson (1996): Characteristics of 4-day oscillations trapped by the Juan de Fuca Ridge. Geophysical Research Letters, 23(13), 1613-1616.

Cannon, G.A., and D.J. Pashinski (1997): Variations in mean currents affecting hydrothermal plumes on the Juan de Fuca Ridge. Journal of Geophysical Research, 102, 24,965-24,976.

Geochemical Transport

Lavelle, J.W., J.P. Cowen, and G.J. Massoth (1992): A model for the deposition of hydrothermal manganese near ridge crests. Journal of Geophysical Research, 97(C5), 7413-7427.