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Observations at the Tidal Plume Front of a High-Volume River Outflow
Geophysical Research Letters
  • Philip M. Orton, Portland State University
  • David A. Jay, Portland State University
Document Type
Publication Date
  • Columbia River (Or. And Wash.) -- Tides -- Analysis,
  • Plumes (Fluid dynamics) -- Mathematical models,
  • Marine ecology
We present shipboard observations of very strong convergence, vertical velocities and mixing, and near-bed impacts associated with the leading-edge front of the tidally-pulsed Columbia River plume. With upwelling-favorable winds and riverflow of 4900 m3s−1, the plume propagates as a buoyant gravity current with a rotary, bore-like vertical frontal circulation and downwelling as strong as 0.35 m s−1. In waters as deep as 65 m, near-bed currents intensify to as much as 1.0 m s−1 after frontal passage, and are often associated with elevated acoustic backscatter. Mixing is locally strong, with an eddy diffusivity of O(0.2 m2s−1) 50 m behind the front, and T-S diagrams imply plume mixing with 10 m deep ocean water. These observations indicate that the leading-edge front of a surface-advected plume can cause exchanges of (a) nutrients between cold subsurface shelf waters and the river plume, and (b) nutrients and sediments across the sediment-water interface.

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Citation Information
Orton, P. M., & Jay, D. A. (2005). Observations at the tidal plume front of a high-volume river outflow. Geophysical Research Letters, 32 (11).