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Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport

Continental Shelf Research

Curt D Storlazzi; Olivia M. Cheriton
By:
ORCID iD , ORCID iD , and ORCID iD
https://doi.org/10.1016/j.csr.2016.03.016

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Abstract

A 6-month deployment of instrumentation from April to October 2012 in 90 m water depth near the outer edge of the mid-shelf mud belt in southern Monterey Bay, California, reveals the importance regional upwelling on water column density structure, potentially accounting for the majority of the variability in internal tidal energy flux across the shelf. Observations consisted of time-series measurements of water-column currents, temperature and salinity, and near-bed currents and suspended matter. The internal tide accounted for 15–25% of the water-column current variance and the barotropic tide accounted for up to 35%. The subtidal flow showed remarkably little shear and was dominated by the 7–14 day band, which is associated with relaxations in the dominant equatorward winds typical of coastal California in the spring and summer. Upwelling and relaxation events resulted in strong near-bed flows and accounted for almost half of the current stress on the seafloor (not accounting for wave orbital velocities), and may have driven along-shelf geostrophic flow during steady state conditions. Several elevated suspended particulate matter (SPM) events occurred within 3 m of the bed and were generally associated with higher, long-period surface waves. However, these peaks in SPM did not coincide with the predicted resuspension events from the modeled combined wave–current shear stress, indicating that the observed SPM at our site was most likely resuspended elsewhere and advected along-isobath. Sediment flux was almost equal in magnitude in the alongshore and cross-shore directions. Instances of wave–current shear stress that exceeded the threshold of resuspension for the silty-clays common at these water depths only occurred when near-bed orbital velocities due to long-period surface waves coincided with vigorous near-bed currents associated with the internal tide or upwelling/relaxation events. Thus upwelling/relaxation dynamics are primarily responsible for variability in the internal tide, as well as transport of near-bottom sediment in the mid-self mud belt during the relatively quiescent summer months.

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Additional publication details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Variability of the internal tide on the southern Monterey Bay continental shelf and associated bottom boundary layer sediment transport
Series title:
Continental Shelf Research
DOI:
10.1016/j.csr.2016.03.016
Volume:
120
Year Published:
2016
Language:
English
Publisher:
Elsevier
Publisher location:
Oxford
Contributing office(s):
Pacific Coastal and Marine Science Center
Description:
14 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Continental Shelf Research
First page:
68
Last page:
81
Country:
United States
State:
California
Other Geospatial:
Monterey Bay
Online Only (Y/N):
N
Additional Online Files (Y/N):
N