Wu Yue

Wu

Yue

0000-0002-0069-9435

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Reabsorption of lee-wave energy in bottom-intensified currents

(American Meteorological Society, 2023-01-19) Wu, Yue ; Kunze, Eric ; Tandon, Amit ; Mahadevan, Amala

While lee-wave generation has been argued to be a major sink for the 1-TW wind work on the ocean’s circulation, microstructure measurements in the Antarctic Circumpolar Currents find dissipation rates as much as an order of magnitude weaker than linear lee-wave generation predictions in bottom-intensified currents. Wave action conservation suggests that a substantial fraction of lee-wave radiation can be reabsorbed into bottom-intensified flows. Numerical simulations are conducted here to investigate generation, reabsorption, and dissipation of internal lee waves in a bottom-intensified, laterally confined jet that resembles a localized abyssal current over bottom topography. For the case of monochromatic topography with | kU 0 | ≈ 0.9 N , where k is the along-stream topographic wavenumber, | U 0 | is the near-bottom flow speed, and N is the buoyancy frequency; Reynolds-decomposed energy conservation is consistent with linear wave action conservation predictions that only 14% of lee-wave generation is dissipated, with the bulk of lee-wave energy flux reabsorbed by the bottom-intensified flow. Thus, water column reabsorption needs to be taken into account as a possible mechanism for reducing the lee-wave dissipative sink for balanced circulation.