Profile of an Isopycnal Surface in the Main Thermocline of the Sargasso Sea

Katz, Eli Joel

doi:10.1175/1520-0485(1973)003<0448:poaisi>2.0.co;2

Cited by 34 publications

(31 citation statements)

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“…Stammer, 1997;Le Traon et al, 2008;Wang et al, 2010), however, has largely ignored the internal-wave field emphasized in earlier works (e.g. Katz, 1973). The internal-wave continuum, as well as tides, inertial oscillations, and mixed-layer flows, may contribute significantly to submesoscale variability.…”

Section: Theoretical Predictions For Submesoscale Wavenumber Spectrasupporting

confidence: 76%

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Submesoscale turbulence in the upper ocean

Callies¹

2016

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Submesoscale flows, current systems 1-100 km in horizontal extent, are increasingly coming into focus as an important component of upper-ocean dynamics. A range of processes have been proposed to energize submesoscale flows, but which process dominates in reality must be determined observationally. We diagnose from observed flow statistics that in the thermocline the dynamics in the submesoscale range transition from geostrophic turbulence at large scales to inertia-gravity waves at small scales, with the transition scale depending dramatically on geographic location. A similar transition is shown to occur in the atmosphere, suggesting intriguing similarities between atmospheric and oceanic dynamics. We furthermore diagnose from upper-ocean observations a seasonal cycle in submesoscale turbulence: fronts and currents are more energetic in the deep wintertime mixed layer than in the summertime seasonal thermocline. This seasonal cycle hints at the importance of baroclinic mixed layer instabilities in energizing submesoscale turbulence in winter. To better understand this energization, three aspects of the dynamics of baroclinic mixed layer instabilities are investigated. First, we formulate a quasigeostrophic model that describes the linear and nonlinear evolution of these instabilities. The simple model reproduces the observed wintertime distribution of energy across scales and depth, suggesting it captures the essence of how the submesoscale range is energized in winter. Second, we investigate how baroclinic instabilities are affected by convection, which is generated by atmospheric forcing and dominates the mixed layer dynamics at small scales. It is found that baroclinic instabilities are remarkably resilient to the presence of convection and develop even when rapid overturns keep the mixed layer unstratified. Third, we discuss the restratification induced by baroclinic mixed layer instabilities. We show that the rate of restratification depends on characteristics of the baroclinic eddies themselves, a dependence not captured by a previously proposed parameterization. These insights sharpen our understanding of submesoscale dynamics and can help focus future inquiry into whether and how submesoscale flows influence the ocean's role in climate.Thesis supervisor: Raffaele Ferrari Title: Breene M. Kerr Professor of Oceanography

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Section: Theoretical Predictions For Submesoscale Wavenumber Spectrasupporting

confidence: 76%

“…Katz (1973) reported on tow experiments in the Sargasso Sea thermocline and showed that spectra on scales between about 50 km and 30 m scaled close to P k ∼ k −2 . He discussed their relation to the GM model spectra, which were later modified to be consistent with these observation (Garrett and Munk, 1975).…”

Section: Mixed-layer Flowsmentioning

confidence: 99%

Submesoscale turbulence in the upper ocean

Callies¹

2016

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“…Katz (1973) reported on tow experiments in the Sargasso Sea thermocline and showed that spectra on scales between about 50 km and 30 m scaled close to P k ; k 22 . He discussed their relation to the GM model spectra, which were later modified to be consistent with these observations (Garrett and Munk 1975).…”

Section: Review Of Previous Observations Of Submesoscale Spectra a Imentioning

confidence: 99%

“…Two variants of geostrophic-turbulence theory have been put forward: interior-QG turbulence (Charney 1971), resulting from deep baroclinic instabilities, and surface-QG turbulence (Blumen 1978), developing in response to frontogenesis. That discussion (e.g., Stammer 1997;Le Traon et al 2008;Wang et al 2010), however, has largely ignored the internal-wave field emphasized in earlier works (e.g., Katz 1973). The internal-wave continuum, as well as tides, inertial oscillations, and mixed layer flows, may contribute significantly to submesoscale variability.…”

Section: Theoretical Predictions For Submesoscale Wavenumber Spectramentioning

confidence: 99%

Interpreting Energy and Tracer Spectra of Upper-Ocean Turbulence in the Submesoscale Range (1–200 km)

Callies

Ferrari

2013

Journal of Physical Oceanography

210

252

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Submesoscale (1-200 km) wavenumber spectra of kinetic and potential energy and tracer variance are obtained from in situ observations in the Gulf Stream region and in the eastern subtropical North Pacific. In the Gulf Stream region, steep kinetic energy spectra at scales between 200 and 20 km are consistent with predictions of interior quasigeostrophic-turbulence theory, both in the mixed layer and in the thermocline. At scales below 20 km, the spectra flatten out, consistent with a growing contribution of internal-wave energy at small scales. In the subtropical North Pacific, the energy spectra are flatter and inconsistent with predictions of interior quasigeostrophic-turbulence theory. The observed spectra and their dependence on depth are also inconsistent with predictions of surface quasigeostrophic-turbulence theory for the observed ocean stratification. It appears that unbalanced motions, most likely internal tides at large scales and the internal-wave continuum at small scales, dominate the energy spectrum throughout the submesoscale range. Spectra of temperature variance along density surfaces, which are not affected by internal tides, are also inconsistent with predictions of geostrophic-turbulence theories. Reasons for this inconsistency could be the injection of energy in the submesoscale range by small-scale baroclinic instabilities or modifications of the spectra by coupling between surface and interior dynamics or by ageostrophic frontal effects.

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“…If the speed of the vessel is large compared to the horizontal phase propagation speed of the waves being observed, spectral analysis of the temperature trace obtained at a gi.ven depth gives a horizontal wave number spectrum of the observed isotherm displacements. Similar observations can be obtained by towing an isotherm-following "fish" behind a research vessel (Katz, 1973(Katz, , 1975.…”

Section: Chapter I Introduction and Historical Reviewmentioning

confidence: 97%

The vertical propagation of inertial waves in the ocean

Leaman¹

1975

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Profile of an Isopycnal Surface in the Main Thermocline of the Sargasso Sea

Cited by 34 publications

References 0 publications

Submesoscale turbulence in the upper ocean

Submesoscale turbulence in the upper ocean

Interpreting Energy and Tracer Spectra of Upper-Ocean Turbulence in the Submesoscale Range (1–200 km)

The vertical propagation of inertial waves in the ocean

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