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Internal Wave Interactions with Equatorial Deep Jets. Part I: Momentum-Flux Divergences

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  • 1 Seattle, Washington
  • | 2 Department of Oceanography, University of Washington, Seattle, Washington
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Abstract

Equatorial deep jets are an unsolved mystery of the equatorial oceans. These alternating zonal currents appear steady over time spans of years, but no postulated energy source has proven plausible, and elevated turbulent dissipation in the jets does not appear to erode them. Transfer of energy between the internal wave field and mean flow can occur through momentum-flux divergences, which could act to maintain the jets. Using a Garrett–Munk spectrum adjusted to the equator, the authors estimate the momentum-flux divergence from internal waves encountering critical layers in deep jets. The net momentum-flux divergences are sensitive to the rate at which wave–wave interactions replenish the internal wave spectrum depleted by critical-layer interactions with adjacent jets. Order-of-magnitude arguments indicate that even modest momentum-flux divergences could dramatically impact the mean flow.

Corresponding author address: Eric Kunze, APL, University of Washington, 1013 NE 40th, Seattle, WA 98105-6698. E-mail: kunze@ocean.washington.edu

Abstract

Equatorial deep jets are an unsolved mystery of the equatorial oceans. These alternating zonal currents appear steady over time spans of years, but no postulated energy source has proven plausible, and elevated turbulent dissipation in the jets does not appear to erode them. Transfer of energy between the internal wave field and mean flow can occur through momentum-flux divergences, which could act to maintain the jets. Using a Garrett–Munk spectrum adjusted to the equator, the authors estimate the momentum-flux divergence from internal waves encountering critical layers in deep jets. The net momentum-flux divergences are sensitive to the rate at which wave–wave interactions replenish the internal wave spectrum depleted by critical-layer interactions with adjacent jets. Order-of-magnitude arguments indicate that even modest momentum-flux divergences could dramatically impact the mean flow.

Corresponding author address: Eric Kunze, APL, University of Washington, 1013 NE 40th, Seattle, WA 98105-6698. E-mail: kunze@ocean.washington.edu

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