Global Abyssal Mixing Inferred from Lowered ADCP Shear and CTD Strain Profiles

Kunze, Eric; Firing, Eric; Hummon, Julia M.; Chereskin, Teresa K.; Thurnherr, Andreas M.

doi:10.1175/jpo2926.1

Cited by 425 publications

(646 citation statements)

References 79 publications

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“…It is noteworthy to mention that this parameterization is able to reproduce the observed levels of dissipation within a factor of two for conditions close to the GM model (Gregg, 1989). The main drawback of the G89 parameterization is that it fails to take into account possible variations of the shear to buoyancy scaled strain variance ratio, R ω , which is a measure of the internal wave field's aspect ratio (Polzin et al, 1995;Kunze et al, 2006). From our measurements we estimate R ω as:…”

Section: A Fine-scale Parameterizationmentioning

confidence: 88%

“…Note that in the final form used by Gregg (1989), j (f/N ) was approximated to unity, following recent works (Kunze et al, 2006;Gregg et al, 2003); we keep the full expression for j (f/N ). In Eq.…”

Section: A Fine-scale Parameterizationmentioning

confidence: 99%

“…denotes an average over a 150 m depth bin. We apply the correction factor proposed by Polzin et al (1995) (and applied by Kunze et al, 2006, andGregg et al, 2003, parameterizations):…”

Section: A Fine-scale Parameterizationmentioning

confidence: 99%

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Characterization of turbulence from a fine-scale parameterization and microstructure measurements in the Mediterranean Sea during the BOUM experiment

Cuypers

Bouruet‐Aubertot

Marec³

et al. 2012

Biogeosciences

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Abstract.One of the main purposes of the BOUM experiment was to find evidence of the possible impact of submesoscale dynamics on biogeochemical cycles. To this aim physical as well as biogeochemical data were collected along a zonal transect through the western and eastern basins of the Mediterranean Sea. Along this transect 3-day fixed point stations were performed within anticyclonic eddies during which microstructure measurements of the temperature gradient were collected over the top 100 m of the water column. We focus here on the characterization of turbulent mixing. The analysis of microstructure measurements revealed a high level of turbulent kinetic energy (TKE) dissipation rate in the seasonal pycnocline and a moderate level below with mean values of the order of 10 −6 W kg −1 and 10 −8 W kg −1 , respectively. The Gregg Henyey (Gregg, 1989) fine-scale parameterization of TKE dissipation rate produced by internal wave breaking, and adapted here following Polzin et al. (1995) to take into account the strain to shear ratio, was first compared to these direct measurements with favorable results. The parameterization was then applied to the whole data set. Within the eddies, a significant increase of dissipation at the top and base of eddies associated with strong near-inertial waves is observed. Vertical turbulent diffusivity is increased both in these regions and in the weakly stratified eddy core. The stations collected along the East-West transect provide an overview of parameterized TKE dissipation rates and vertical turbulent diffusivity over a latitudinal section of the Mediterranean Sea. Strong TKE dissipation rates are found within the first 500 m and up to 1500 m above the bottom. Close to the bottom where the stratification is weak, the inferred vertical turbulent diffusivity can reach K z 10 −3 m 2 s −1 and may therefore have a strong impact on the upward diffusive transport of deep waters masses.

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Section: A Fine-scale Parameterizationmentioning

confidence: 88%

Section: A Fine-scale Parameterizationmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of turbulence from a fine-scale parameterization and microstructure measurements in the Mediterranean Sea during the BOUM experiment

Cuypers

Bouruet‐Aubertot

Marec³

et al. 2012

Biogeosciences

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“…On a global scale, closing the overturning circulation requires the production of dense water at high latitudes to be balanced by buoyancy gain elsewhere. Observational evidence collected during the last few decades indicates that, except near the sea surface, diapycnal buoyancy fluxes are elevated primarily near topography, in particular over the rough flanks of mid-ocean ridges (Polzin et al, 1997;Kunze et al, 2006). On regional scales, circulation and mixing near the crests of mid-ocean ridges largely control the initial dispersal of materials released at hydrothermal sources (e.g.…”

Section: Introductionmentioning

confidence: 99%

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Thurnherr

Ledwell

Lavelle

et al. 2011

Deep Sea Research Part I: Oceanographic Research Papers

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1ABSTRACT. Topography has a strong effect on the physical oceanography over the flanks and crests of the global mid-ocean ridge system. Here, we present an analysis of the hydrography and circulation near the crest of the East Pacific Rise (EPR) between 9 • and 10 • N, which coincides with an integrated study site (ISS) of the RIDGE2000 program. The analysis is based primarily on survey and mooring data collected during the LADDER project, which aimed to investigate oceanographic and topographic influences on larval retention and dispersal in hydrothermal vent communities. Results indicate that the yearly averaged regional mean circulation is characterized by a westward drift of 0.5-1 cm·s −1 across the EPR axis and by north-and southward flows along the western and eastern upper ridge flanks, respectively. The westward drift is part of a basin-scale zonal flow that extends across most of the Pacific ocean near 10 • N, whereas the meridional currents near the ridge crest are a topographic effect. In spite of considerable mesoscale variability, which dominates the regional circulation and dispersal on weekly to monthly time scales, quasi-synoptic surveys carried out during the mooring deployment and recovery cruises indicate subinertial circulations that are qualitatively similar to the yearly averaged flow but associated with significantly stronger velocities. Weekly averaged mooring data indicate that the anticyclonically sheared along-flank flows are associated with core speeds as high as 10 cm·s −1 and extend ≈10 km off axis and 200 m above the ridge-crest topography. Near the northern limit of the study region, the Lamont Seamount Chain rises from the western ridge flank and restricts along-EPR flow to five narrow passages, where peak velocities in excess of 20 cm·s −1 were observed. Outside the region of the ridge-crest boundary currents the density field over the EPR near 10 • N is characterized by isopycnals dipping into the ridge flanks. Directly above the EPR axis the ridge-crest boundary currents give rise to an isopycnal dome. During times of strong westward cross-EPR flow isopycnal uplift over the eastern flank causes the cross-ridge density field below the doming isopycnals to be asymmetric, with higher densities over the eastern than over the western flank.

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“…According to the results of Kunze et al (2006) and Wunsch and Ferrari (2004), in a global average it is appropriate to use constant values of the diffusion coefficient, k, and of the speed of advection, ω. For k a constant value (1.0 ×10 -5 m 2 /s) was used, whereas for the advection speed a steady profile which decreases in magnitude with depth z was used, ω(z) = 0.045 cm/day [-1 + 0.08 tanh (0.001 m -1 • z -0.03)].…”

Section: Deterministic Climate Modelmentioning

confidence: 99%

Analysis of the simulated global temperature using a simple energy balance stochastic model

Moreles

Martínez‐López

2016

ATM

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Este trabajo presenta un estudio de la respuesta de la variabilidad simulada de la temperatura global a parametrizaciones estocásticas aditivas y multiplicativas de flujos de calor, junto con una descripción de la variabilidad de largo plazo en términos de procesos autorregresivos simples. Para simular la temperatura global de la Tierra se utilizó un modelo climático de balance de energía promediado globalmente, acoplado a un modelo oceánico termodinámico. Se encontró que procesos autorregresivos simples explican la variabilidad de la temperatura en el caso de parametrizaciones aditivas; sin embargo, en el caso de parametrizaciones multiplicativas, la descripción de la variabilidad de la temperatura involucraría procesos autorregresivos de orden superior, lo cual sugiere la presencia de mecanismos complejos de retroefecto originados por el forzamiento multiplicativo. Asimismo, se encontró que las parametrizaciones multiplicativas produjeron una estructura compleja que emula de manera cercana procesos climáticos observados. Finalmente, se propone un nuevo enfoque para describir la estabilidad de un sistema estocástico general unidimensional en estado estacionario, a través de su función potencial. A partir de una expresión analítica de la función potencial se profundizó en la descripción de un sistema estocástico. ABSTRACTThis work presents a study of the response of the simulated global temperature variability to additive and multiplicative stochastic parameterizations of heat fluxes, along with a description of the long-term variability in terms of simple autoregressive processes. The Earth's global temperature was simulated using a globally averaged energy balance climate model coupled to a thermodynamic ocean model. It was found that simple autoregressive processes explain the temperature variability in the case of additive parameterizations; whereas in the case of multiplicative parameterizations, the description of the temperature variability would involve higher order autoregressive processes, suggesting the presence of complex feedback mechanisms originated by the multiplicative forcing. Also, it was found that multiplicative parameterizations produced a rich structure that emulates closely observed climate processes. Finally, a new approach to describe the stability in the steady state of a general one-dimensional stochastic system, through its potential function, was proposed. From an analytical expression of the potential function, further insight into the description of a stochastic system was provided.

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Global Abyssal Mixing Inferred from Lowered ADCP Shear and CTD Strain Profiles

Cited by 425 publications

References 79 publications

Characterization of turbulence from a fine-scale parameterization and microstructure measurements in the Mediterranean Sea during the BOUM experiment

Characterization of turbulence from a fine-scale parameterization and microstructure measurements in the Mediterranean Sea during the BOUM experiment

Hydrography and circulation near the crest of the East Pacific Rise between 9° and 10°N

Analysis of the simulated global temperature using a simple energy balance stochastic model

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