Detailed observations of a naturally occurring shear instability

Seim, Harvey; Gregg, Michael C.

doi:10.1029/94jc00168

Cited by 78 publications

(59 citation statements)

References 33 publications

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“…Unfortunately, neither the violation of physical conditions nor sampling error can be verified with the current measurements. The billow-tracking observations of Seim and Gregg (1994) support the latter explanation in the context of K-H instabilities, albeit with ''wide scatter'' and fewer observed overturns than reported here. Additional campaigns tracking billows like those generated at IWISE L are needed to separate sampling biases from physically based biases that may exist.…”

Section: Discussionsupporting

confidence: 64%

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Biases in Thorpe-Scale Estimates of Turbulence Dissipation. Part I: Assessments from Large-Scale Overturns in Oceanographic Data

Mater

Venayagamoorthy

Laurent

et al. 2015

Journal of Physical Oceanography

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Oceanic density overturns are commonly used to parameterize the dissipation rate of turbulent kinetic energy. This method assumes a linear scaling between the Thorpe length scale L T and the Ozmidov length scale L O . Historic evidence supporting L T ; L O has been shown for relatively weak shear-driven turbulence of the thermocline; however, little support for the method exists in regions of turbulence driven by the convective collapse of topographically influenced overturns that are large by open-ocean standards. This study presents a direct comparison of L T and L O , using vertical profiles of temperature and microstructure shear collected in the Luzon Strait-a site characterized by topographically influenced overturns up to O(100) m in scale. The comparison is also done for open-ocean sites in the Brazil basin and North Atlantic where overturns are generally smaller and due to different processes. A key result is that L T /L O increases with overturn size in a fashion similar to that observed in numerical studies of Kelvin-Helmholtz (K-H) instabilities for all sites but is most clear in data from the Luzon Strait. Resultant bias in parameterized dissipation is mitigated by ensemble averaging; however, a positive bias appears when instantaneous observations are depth and time integrated. For a series of profiles taken during a spring tidal period in the Luzon Strait, the integrated value is nearly an order of magnitude larger than that based on the microstructure observations. Physical arguments supporting L T ; L O are revisited, and conceptual regimes explaining the relationship between L T /L O and a nondimensional overturn size c L T are proposed. In a companion paper, Scotti obtains similar conclusions from energetics arguments and simulations.

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Section: Discussionsupporting

confidence: 64%

“…Observations tracking billows over their life cycle in geophysical flows are rare. However, the K-H billow-following observations of Seim and Gregg (1994) …”

Section: Introductionmentioning

confidence: 99%

Biases in Thorpe-Scale Estimates of Turbulence Dissipation. Part I: Assessments from Large-Scale Overturns in Oceanographic Data

Mater

Venayagamoorthy

Laurent

et al. 2015

Journal of Physical Oceanography

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“…In rnany oceanic environments, this is a valid assumption; however there exist numerous regions of the ocean where physical scattering processes are strong enough to provide detectable amounts of acoustic scattering (for example Haury et ale (1983); Sandstrom et oJ. (1989); Seim and Gregg (1994);TrevoITow and Teichrob (1994); Trevorrow (1998)). …”

Section: Ton and Microstructurementioning

confidence: 99%

Estimating Gulf of Maine zooplankton distributions using multiple frequency acoustic, video and environmental data

Warren¹

2001

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This thesis develops methods useful for estimating zooplankton distributions in the field by combining acoustic models and an integrated set of field data. The accnracy of existing models for fluid-like and elastic-shelled animals is determined by analysis of scattering data from individual aninials in a laboratory tank. Results indicate that simple two-ray scattering rnodels are accurate and allow predictions of size or orientation of an animal to be made for certain animal orientations. A model for gas-bearing zooplankton is compared with in sit'l multiple frequency acoustic measurements from siphonophores. Estimates of the numerical density of these animals are made using echo integration data from a scientific echo-sounder. Multiple frequency acoustic scattering data from a survey of an internal wave are analyzed to determine the contributions from biologieal and physical sources. Net tow data provide information about biological scatterers while temperature and salinity profiles are used with a theoretical model to predict contributions from physical sources. Results indicate that scattering from physical sources is comparable to that from biological sources in certain regions and that spectra may be used to distinguish these sources. Improved estimates of biomass from acoustic scatteriug data were made by accounting for the scattering contributions from physical sources. This is the first work to quantify the scattering contributions from biological and physical sources of scattering in a field study. It is better to fail in originality than to succeed in iniitation. He who has never failed somewhere, that man cannot be great. If it be said that continual snccess is proof that a man wisely knows his powers, it is only to be added that, in that ease, he knows them to be smaIL Hennan MelvilleDon't believe the hype. That ¡nade the school a place of decent order vVhere books were read and sums were proven true And paper maps t.hat showed t.he land and water vVere held up as the real wide world to you. Always, he kept his eyes upon his books:And now he has grown to be a man fellow .II' classmates are an exceptional group of people, not to mention they're all wicked srnart.From the initial pot-lucks to the defense parties, it's been a fantastic group of people t.o have as my peers.Ann P. was always up for a "date". Liz K. survived 10 hours in a ear with me and didn't have to be institutionalized. Sheri \V. never tackled me too hard while playing rugby. Brenda J. attended Lollapalooza 5 with me. Nicole P. survived with me during our thesis writing. i'ike A. reminded me you're never too old to have fun. 'rom i'd., Lou StL., and l'like B. were the original members of VomeletLe. Suzie \V.enthusiasm for school was a contrast to mine. Fellow NRQ members ,Albert and i'ak, made the last 6 months of school very survivable. Doc Reddy made the best brunclics I've ever eaten, taught me many acronyms, was a co-founder of PNF and rescued me after my kayak was attacked a rogue buoy.

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“…The development of shear instabilities (or Kelvin-Helmholtz instabilities) is thought to be the primary mechanism by which mixing is enhanced within the pycnocline of partially stratified estuaries [e.g., Geyer and Seim and Gregg, 1994;Zhou, 1998]. The fjordlike systems that are hydraulically controlled by a sill or latter have proven to be a useful visualization tool of these constriction at their mouths show such features [e.g., Farmer instabilities.…”

Section: Introductionmentioning

confidence: 99%

Shear instability in the St. Lawrence Estuary, Canada: A comparison of fine‐scale observations and estuarine circulation model results

Bourgault¹,

Saucier²,

Lin³

2001

J. Geophys. Res.

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Detailed observations of a naturally occurring shear instability

Cited by 78 publications

References 33 publications

Biases in Thorpe-Scale Estimates of Turbulence Dissipation. Part I: Assessments from Large-Scale Overturns in Oceanographic Data

Biases in Thorpe-Scale Estimates of Turbulence Dissipation. Part I: Assessments from Large-Scale Overturns in Oceanographic Data

Estimating Gulf of Maine zooplankton distributions using multiple frequency acoustic, video and environmental data

Shear instability in the St. Lawrence Estuary, Canada: A comparison of fine‐scale observations and estuarine circulation model results

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