Numerical simulation of mean currents and water property anomalies at Endeavour Ridge: Hydrothermal versus topographic forcing

Abstract

Numerical simulations based on realistic seafloor topography are used to examine near-bottom currents in the region of the Endeavour segment of Juan de Fuca Ridge (Endeavour Ridge) in the northeast Pacific. Results support earlier findings that hydrothermal venting within the ∼2200-m deep axial valley, rather than topographically modified, basin-scale cross-ridge geostrophic flow, is responsible for the near-steady northward currents observed within the confines of the valley. Although it does not generate deep flow within the valley, the basin-scale circulation determines the horizontal redistribution of the hydrothermal plumes once they rise above the ridge crest. Simulations of the near-bottom temperature and salinity fields reveal that model runs that incorporate a deep westward background flow most closely reproduce the observed plume anomaly distributions above the ridge, indicating that bottom currents in the region are predominantly westward, counter to the prevailing southeasterly flow of the wind-driven California Current in the upper half of the water column.