Numerical simulation of hydrothermal vent-induced circulation at Endeavour Ridge

Abstract

[1] Hydrothermal venting at Endeavour Ridge is focused at five major vent fields spaced at ∼2-km intervals along a narrow (∼1 km wide) north-south trending rift-valley. A Princeton Ocean Model with an axially symmetric rift-valley centered within a rotating, full-depth (2400 m) stratified ocean is used to simulate the circulation and associated temperature and salinity fields generated by vertical heat fluxes from the five vent fields. Steady seafloor heat fluxes are introduced instantaneously to a quiescent ocean using the model provision for boundary fluxes. The model achieves a quasi-steady state in about 80 days. Results are consistent with observation. In particular, buoyant plumes emanating from the larger vent fields rise to "trapping" depths as shallow as 1850 m (∼350 m above bottom) and spread laterally with the vent-induced circulation. Plume anomalies remain confined to within several kilometers of the ridge, except to the west where anomalies extend more than 10 km off-axis. As with observations, modeled currents within the valley consist of a strong (∼10 cm s-1) poleward inflow within roughly 75 m of the bottom and an equally strong equatorward counterflow above that depth. Weak (∼1 cm s-1) equatorward flow develops over the flank of the west ridge and weak poleward flow over the flank of the east ridge. Cyclonic relative vorticity dominates the model circulation within the valley while anticyclonic vorticity prevails above the depth of neutral plume buoyancy. Findings support the notion that turbulent entrainment by buoyant plumes forces a mean poleward flow within the confines of the Endeavour Ridge axial valley. Copyright 2005 by the American Geophysical Union.