Fine‐scale temperature variability: The influence of near‐inertial waves

Marmorino, G. O.; Rosenblum, Lawrence; Trump, C. L.

doi:10.1029/jc092ic12p13049

Cited by 56 publications

(29 citation statements)

References 21 publications

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“…Marmorino et al, 1987;Moum et al, 1992;Brandt et al, 1999). These thermistor strings had an accuracy of ∼10 −2 • C (Marmorino et al, 1987;Selschopp, 1997). As suggested from the "moored" observations by Thorpe (1987) and Hosegood et al (2004), such temperature variations can be expected even in deepocean environments, despite the local background buoyancy period, which is relatively large O(10-100 min).…”

Section: Introductionmentioning

confidence: 76%

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High sampling rate thermistor string observations at the slope of Great Meteor Seamount

et al. 2005

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Abstract.A high sampling rate (1 Hz) thermistor string has been built to accommodate the scientific need to accurately monitor high-frequency and vigorous internal wave and overturning processes in the ocean. The thermistors and their custom designed electronics can register temperature at an estimated precision of about 0.001 • C with a response time faster than 0.25 s down to depths of 6000 m. With a quick in situ calibration using SBE 911 CTD an absolute accuracy of 0.005 • C is obtained. The present string holds 128 sensors at 0.5 m intervals, which are all read-out within 0.5 s. When sampling at 1 Hz, the batteries and the memory capacity of the recorder allow for deployments of up to 2 weeks. In this paper, the instrument is described in some detail. Its performance is illustrated with examples from the first moored observations, which show Kelvin-Helmholtz overturning and very high-frequency (Doppler-shifted) internal waves besides occasionally large turbulent bores moving up the sloping side of Great Meteor Seamount, Canary Basin, North-Atlantic Ocean.

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Section: Introductionmentioning

confidence: 76%

“…whilst sampling at 0.1-4 Hz (e.g. Marmorino et al, 1987;Moum et al, 1992;Brandt et al, 1999). These thermistor strings had an accuracy of ∼10 −2 • C (Marmorino et al, 1987;Selschopp, 1997).…”

Section: Introductionmentioning

confidence: 99%

High sampling rate thermistor string observations at the slope of Great Meteor Seamount

et al. 2005

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“…Presently, this is impossible, but some progress has been made by the construction of high sampling-rate thermistors. 2,9,10 Initially, 1-Hz sampling-rate thermistors could only be used in a towed fashion cabled to a ship, 2 but modern electronics allow stand-alone sensors that can operate uninterruptedly for a period of a year. 10 When many are used, say 100 at 1 m intervals, time-depth images can be obtained that resolve internal waves and the larger, most energetic turbulence scales, provided the sensors' noise level and precision are sufficiently small (typically 0.001 • C or less).…”

Section: Introductionmentioning

confidence: 99%

“…It results in tens of meters high internal wave amplitudes and an ocean which is permanently in "wave motion." 2,3 Typical internal wave periods range from one day (at mid-latitudes) to one hour, in the deep ocean, and a few minutes, near the ocean surface. Typical (internal-wave-generated) turbulence scales vary from several tens of meters, the internal wave height and the buoyancy scale, to a few millimeters, the dissipation scale.…”

Section: Introductionmentioning

confidence: 99%

Stratified turbulence and small-scale internal waves above deep-ocean topography

Haren

2013

Physics of Fluids

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When ocean's internal tidal waves "beach" at underwater topography, they transform from more or less linear into highly nonlinear waves that can break with generation of vigorous turbulent mixing. Although most mixing occurs in the half hour around a steep (bottom-)front leading the upslope moving internal tide phase, relatively large mixing also occurs some distance of several tens of meters off the bottom, just prior to the downslope moving internal tide phase and initiated by highfrequency "small-scale" internal waves. Details of this off-bottom small-scale mixing in a stratified natural environment and some of its variability per tidal period are presented here in two case studies using high-resolution temperature observations (61 sensors at 1 m intervals; <10 −3 • C precision) at a 969 m deep site south of New Zealand. The observations shed some light on stratified turbulence that is generated in a relatively thick (∼30 m) weakly stratified layer and in the strongly stratified interfaces above and below. The interfacial internal waves generate turbulence with largest dissipation rate and temperature variance at the edge of the upper interface and the weakly stratified layer. When these waves steep nonlinearly, immediate moderate turbulence generation is observed below, throughout the weakly stratified layer. Largest turbulence is generated by 25 m high asymmetric Holmboe overturns. C 2013 AIP Publishing LLC. [http://dx

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“…Toole et al, 1987). In the surface layers mixing is also associated with inertial motions that develop over the seasonal thermocline (Marmorino et al, 1987;Gregg et al, 1986), with the baroclinic upwelling jet (Kundu and Beardsley, 1991), or with the interaction of the two processes (Pelegrí and Richman, 1993). Pelegrí andCsanady (1991, 1994) found compelling evidence of intense diapycnal mixing within the Gulf Stream and suggested that it may be linked to mesoscale activity along its path.…”

Section: Introductionmentioning

confidence: 99%

Estimates of gradient Richardson numbers from vertically smoothed data in the Gulf Stream region

Gastel¹,

Pelegrí²

2004

Sci. Mar.

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SUMMARY: We use several hydrographic and velocity sections crossing the Gulf Stream to examine how the gradient Richardson number, Ri, is modified due to both vertical smoothing of the hydrographic and/or velocity fields and the assumption of parallel or geostrophic flow. Vertical smoothing of the original (25 m interval) velocity field leads to a substantial increase in the Ri mean value, of the same order as the smoothing factor, while its standard deviation remains approximately constant. This contrasts with very minor changes in the distribution of the Ri values due to vertical smoothing of the density field over similar lengths. Mean geostrophic Ri values remain always above the actual unsmoothed Ri values, commonly one to two orders of magnitude larger, but the standard deviation is typically a factor of five larger in geostrophic than in actual Ri values. At high vertical wavenumbers (length scales below 3 m) the geostrophic shear only leads to near critical conditions in already rather mixed regions. At these scales, hence, the major contributor to shear mixing is likely to come from the interaction of the background flow with internal waves. At low vertical wavenumbers (scales above 25 m) the ageostrophic motions provide the main source for shear, with cross-stream movements having a minor but non-negligible contribution. These large-scale motions may be associated with local accelerations taking place during frontogenetic phases of meanders. -Hemos utilizado varias secciones hidrográficas y de velocidad, que atraviesan la Corriente del Golfo, con el fin de analizar como se modifica el número de gradiente de Richardson, Ri, debido tanto al suavizado vertical de los datos hidrográficos y de velocidad como a la aproximación de flujo geostrófico paralelo. El suavizado vertical de los datos originales de velocidad (intervalo de 25 m) conlleva un aumento substancial del valor medio de Ri, del mismo orden que el factor de suavizado, mientras que la desviación estándar permanece aproximadamente constante. Esto contrasta con los cambios muy pequeños en la distribución de los valores de Ri causados por el suavizado vertical del campo de densidades sobre distancias similares. Los valores medios geostróficos de Ri permanecen siempre por encima de los valores de Ri obtenidos mediante los datos originales de velocidad sin suavizar, típicamente uno o dos órdenes de magnitud mayores, mientras que la desviación estándar de los valores geostróficos usualmente es unas cinco veces mayor que la de los valores reales de Ri. En números de onda verticales altos (escalas de longitud por debajo de 3 m) la cizalla geostrófica solo ocasiona condiciones casi críticas in regiones que ya se encuentran bastante mezcladas. En estas escalas, por tanto, la mayor contribución a la mezcla por cizalla probablemente proviene de la interacción entre el flujo base y las ondas internas. En números de onda verticales bajos (escalas por arriba de 25 m) los movimientos geostróficos proporcionan la fuente principal de cizalla, teniendo los movimie...

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Fine‐scale temperature variability: The influence of near‐inertial waves

Cited by 56 publications

References 21 publications

High sampling rate thermistor string observations at the slope of Great Meteor Seamount

High sampling rate thermistor string observations at the slope of Great Meteor Seamount

Stratified turbulence and small-scale internal waves above deep-ocean topography

Estimates of gradient Richardson numbers from vertically smoothed data in the Gulf Stream region

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