Observed Energy Exchange between Low-Frequency Flows and Internal Waves in the Gulf of Mexico
Title: Observed Energy Exchange between Low-Frequency Flows and Internal Waves in the Gulf of Mexico
Journal: Journal of Physical Oceanography, 48: 995-1008
Authors: JING Z.*, P. Chang, S. DiMarco and L. -X. Wu
Abstract: A long-term mooring array deployed in the northern Gulf of Mexico is used to analyze energy exchange between internal waves and low-frequency flows. In the subthermocline (245–450 m), there is a noticeable net energy transfer from low-frequency flows, defined as having a period longer than six inertial periods, to internal waves. The magnitude of energy transfer rate depends on the Okubo–Weiss parameter of low-frequency flows. A permanent energy exchange occurs only when the Okubo–Weiss parameter is positive. The near-inertial internal waves (NIWs) make major contribution to the energy exchange owing to their energetic wave stress and relatively stronger interaction with low-frequency flows compared to the high-frequency internal waves. There is some evidence that the permanent energy exchange between low-frequency flows and NIWs is attributed to the partial realization of the wave capture mechanism. In the periods favoring the occurrence of the wave capture mechanism, the horizontal propagation direction of NIWs becomes anisotropic and exhibits evident tendency toward that predicted from the wave capture mechanism, leading to pronounced energy transfer from low-frequency flows to NIWs.