Instabilities in nonlinear internal waves on the Washington continental shelf

Zhang, Shuang; Alford, Matthew H.

doi:10.1002/2014jc010638

i

Instabilities in nonlinear internal waves on the Washington continental shelf

Supporting Files

2015
By Zhang, Shuang ; Alford, Matthew H.

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Journal Title:

Journal of Geophysical Research: Oceans
Personal Author:

Zhang, Shuang ; Alford, Matthew H.
NOAA Program & Office:

NOS (National Ocean Service)
Description:

Previous studies have identified two primary mechanisms (shear instability and convective instability) by which nonlinear internal waves (NLIWs) induce mixing on continental shelves. To determine the relative importance of these and their dependence on background flow conditions, we examine a much longer (6 month) data set from a moored ADCP/thermistor chain with 2 m vertical spacing in which over 600 NLIWs are detected. Turbulent properties of the 318 waves with detectable overturning instabilities are documented using Thorpe scales. The 130 waves detected while an ADCP was functioning are classified based on a Froude number criterion (Fr = urn:x-wiley:21699275:media:jgrc21330:jgrc21330-math-0001, where u is velocity in the wave propagation direction, c is the wave phase speed). Of these, 108 waves are identified as shear-instability (Type I; Fr < 1) waves and 22 as convective instability (Type II; Fr > 1). Composites are constructed by averaging in a wave coordinate frame over all waves in each category, showing the mean spatial structure of dissipation and other wave quantities. Turbulence is highest at the sheared interface for Type I waves and throughout the wave core for Type II waves. No relationship between wave instability mechanisms and wave/background parameters such as wave steepness, stratification, or mean flow is found, except that unstable waves tend to be more energetic, demonstrating a need to better understand wave propagation and breaking in complex and variable coastal oceanographic background flows.
Keywords:

Earth And Planetary Sciences (miscellaneous) Geochemistry And Petrology Geophysics Oceanography Space And Planetary Science Earth And Planetary Sciences (miscellaneous) Geochemistry And Petrology Space And Planetary Science Earth And Planetary Sciences (miscellaneous) Geochemistry And Petrology Space And Planetary Science
Source:

Journal of Geophysical Research: Oceans, 120(7), 5272-5283
DOI:

https://doi.org/10.1002/2014jc010638
ISSN:

2169-9275
Format:

PDF
Publisher:

American Geophysical Union (AGU)
Document Type:

Journal Article
Funding:

Grant no. NA11NOS0120036
Rights Information:

Other
Compliance:

Library
Main Document Checksum:

urn:sha256:a38cca7ae2120626067d5ffabee6ec237af55f9217b780b5cb4462918ce3bfd0
Download URL:

https://repository.library.noaa.gov/view/noaa/59862/noaa_59862_DS1.pdf
File Type:

[PDF - 4.70 MB ]

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