The subinertial variability of deep-ocean currents near the crest of the East Pacific Rise in the tropical East Pacific is examined using observations from a collection of moored instruments augmented with sea-surface height data. The moored velocity observations reveal low-frequency currents with characteristic time scales of 1–3 months and maximum speeds up to 10 cm/s. Directly over the ridge axis, the subinertial motions are dominated by the along-axial (meridional) velocities, which are coherent in phase and amplitude along the entire length of the ridge segment between 9 and 10N. With increasing distance from the ridge crest the low-frequency currents become weaker and less dominated by the along-axial flow component. Lag-correlations between the velocity records indicate westward signal propagation with a speed on the same order as the speed of westward-propagating sea-surface height anomalies, which are also associated with characteristic time scales of 1–3 months. As, furthermore, the subinertial velocities at depth are significantly correlated with geostrophic near-surface currents estimated from sea-surface height data, we conclude that the subinertial velocity field near the EPR crest is mainly a superposition of velocities associated with eddies propagating westward across the ridge and “topographic flows”, such as trapped waves and boundary currents.
Subinertial variability in the deep ocean near the East Pacific Rise between 9° and 10°N
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Geophysical Research Letters
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