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Interactions between waves, sediment, and turbulence on a shallow estuarine mudflat

Journal of Geophysical Research C: Oceans

By:
and
DOI: 10.1002/2013JC009477

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Abstract

Measurements were collected on a shallow estuarine mudflat in northern San Francisco Bay to examine the physical processes controlling waves, turbulence, sediment resuspension, and their interactions. Tides alone forced weak to moderate currents of 10–30 cm s-1 in depths of 0–3 m, and maintained a background suspension of 30–50 mg L21 of fine sediment. In the presence of wind waves, bottom orbital velocities spanned 20–30 cm s-1, suspended-sediment concentrations (SSC) at 15 and 30 cm above the bed (cmab) increased by 1–2 orders of magnitude, and vertical gradients in SSC were strong enough to produce turbulence-limiting stratification, with gradient Richardson numbers exceeding 0.25. Simultaneously, turbulent stresses (decomposed from wave motions) increased by an order of magnitude. The apparent contradiction of energetic turbulence in the presence of strong stratification was reconciled by considering the turbulent kinetic energy (TKE) budget: in general, dissipation and buoyancy flux were balanced by local shear production, and each of these terms increased during wave events. The classic wave-current boundary layer model represented the observations qualitatively, but not quantitatively since the velocity profile could not be approximated as logarithmic. Rather, the mean shear was elevated by the Stokes drift return flow and wind-generated surface stress, which diffused sediment upward and limited stratification. Our findings highlight a pathway for waves to supply energy to both the production and destruction of turbulence, and demonstrate that in such shallow depths, TKE and SSC can be elevated over more of the water column than predicted by traditional models.

Geospatial Extents

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Interactions between waves, sediment, and turbulence on a shallow estuarine mudflat
Series title:
Journal of Geophysical Research C: Oceans
DOI:
10.1002/2013JC009477
Volume
119
Issue:
3
Year Published:
2014
Language:
English
Publisher:
American Geophysical Union
Contributing office(s):
Pacific Coastal and Marine Science Center
Description:
20 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Geophysical Research C: Oceans
First page:
1534
Last page:
1553
Country:
United States
State:
California
Other Geospatial:
San Pablo Bay