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Observations at the tidal plume front of a high‐volume river outflow
Author(s) -
Orton Philip M.,
Jay David A.
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl022372
Subject(s) - plume , downwelling , front (military) , geology , upwelling , outflow , oceanography , panache , gravity current , mixing (physics) , deep ocean water , advection , eddy diffusion , current (fluid) , atmospheric sciences , deep sea , turbulence , meteorology , internal wave , physics , quantum mechanics , thermodynamics
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 m 3 s −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 m 2 s −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.