Observations of internal waves and associated mixing phenomena in the Portimao Canyon area

Bruno, Miguel; Vázquez, Águeda; Gómez-Enri, Jesús; Vargas, J. Mario; García‐Lafuente, Jesús; Ruiz-Cañavate, A.; Mariscal, Luis; Vidal, Juan

doi:10.1016/j.dsr2.2006.04.015

Cited by 31 publications

(23 citation statements)

References 16 publications

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“…9; Table 5; Hüneke, 2006). Tidal currents are worldwide features known from the shelf (Bruno et al. , 2006) and from open ocean environments (Fig.…”

Section: Factors Controlling Pervasive Marine Carbonate Cementation Imentioning

confidence: 99%

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

et al. 2010

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The controlling parameters of early marine carbonate cementation in shoal water and hemipelagic to pelagic domains are well‐studied. In contrast, the mechanisms driving the precipitation of early marine carbonate cements at deeper slope settings have received less attention, despite the fact that considerable volumes of early marine cement are present at recent and fossil carbonate slopes in water depths of several hundreds of metres. In order to better understand the controlling factors of pervasive early marine cementation at greater water depths, marine carbonate cements observed along time‐parallel platform to basin transects of two intact Pennsylvanian carbonate slopes are compared with those present in the slope deposits of the Permian Capitan Reef and Neogene Mururoa Atoll. In all four settings, significant amounts of marine cements occlude primary pore spaces downslope into thermoclinal water depths, i.e. in a bathymetric range between some tens and several hundreds of metres. Radial, radiaxial and fascicular optic fibrous calcites, and radiaxial prismatic calcites are associated with re‐deposited facies, boundstones and rudstones. Botryoidal (formerly) aragonitic precipitates are common in microbially induced limestones. From these case studies, it is tentatively concluded that sea water circulation in an extensive, near‐sea floor pore system is a first‐order control on carbonate ion supply and marine cementation. Coastal upwelling and internal or tidal currents are the most probable mechanisms driving pore water circulation at these depths. Carbonate cements precipitated under conditions of normal to elevated alkalinity, locally elevated nutrient levels and variable sea water temperatures. The implications of these findings and suggestions for future work are discussed.

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“…9; Table 5; Hüneke, 2006). Tidal currents are worldwide features known from the shelf (Bruno et al. , 2006) and from open ocean environments (Fig.…”

Section: Factors Controlling Pervasive Marine Carbonate Cementation Imentioning

confidence: 99%

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

et al. 2010

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“…It has also been proposed (based on observations in Monterey Canyon) that small scale roughness in the canyon is responsible for much of the internal tidal energy . Internal waves with periods shorter than that of tides are also enhanced in canyons and have been hypothesized to be generated by the tides (Bruno et al, 2006). In contrast, nearinertial energy is not enhanced by canyons probably due to the canyon walls interfering with these long wavelength waves (Wunsch and Webb, 1979;Keen and Allen, 2000).…”

Section: Enhanced Internal Tides and Mixing In Canyonsmentioning

confidence: 99%

“…These models allow investigation of the details and emphasizes the influence of topographic features upon the flow patterns, the changes in the geometry of the dense water plume and the mixing with surrounding waters. In some canyons, the occurrence of dense water bottom flows could be inferred from peculiar bed depositional and erosional bedforms, such as fields, moats, furrows and comet marks (Canals et al, 2006;Puig et al, 2008;De Santis et al, 2007;Trincardi et al, 2007). Studies performed in the Mediterranean Sea reveal the prevalence of canyon-driven dense-water cascading.…”

Section: Observationsmentioning

confidence: 99%

“…Studies performed in the Mediterranean Sea reveal the prevalence of canyon-driven dense-water cascading. In the western Mediterranean, dense shelf water has been shown to be formed on the Gulf of Lion and adjacent Catalan shelves (Dufau-Julliand et al, 2004;Canals et al, 2006;Ulses et al, 2008a and the references therein). Both observations and modelling show the influence of canyons, in particular the Cap de Creus Canyon which channeled most of the dense water formed on these shelves.…”

Section: Observationsmentioning

confidence: 99%

“…Dense shelf water cascading contributes to the ventilation of intermediate and deep waters of the oceans and has a significant impact on biogeochemical cycles by entraining significant quantities of minerals and organic material both dissolved and particulate (Hill et al, 1998;Niemann et al, 2004;Canals et al, 2009;Vilibic and Santic, 2008).…”

Section: Formation Of Dense Water On Shelvesmentioning

confidence: 99%

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A review of the role of submarine canyons in deep-ocean exchange with the shelf

2009

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Abstract. Cross shelf-break exchange is limited by the tendency of geostrophic flow to follow bathymetric contours, not cross them. However, small scale topography, such as canyons, can reduce the local lengthscale of the flow and increase the local Rossby number. These higher Rossby numbers mean the flow is no longer purely geostrophic and significant cross-isobath flow can occur. This cross-isobath flow includes both upwelling and downwelling due to wind-driven shelf currents and the strong cascading flows of dense shelfwater into the ocean. Tidal currents usually run primarily parallel to the shelf-break topography. Canyons cut across these flows and thus are often regions of generation of strong baroclinic tides and internal waves. Canyons can also focus internal waves. Both processes lead to greatly elevated levels of mixing. Thus, through both advection and mixing processes, canyons can enhance Deep Ocean Shelf Exchange. Here we review the state of the science describing the dynamics of the flows and suggest further areas of research, particularly into quantifying fluxes of nutrients and carbon as well as heat and salt through canyons.

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Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high‐resolution MCS data

Sallarès

Mojica

Biescas

et al. 2016

Geophysical Research Letters

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Part of the kinetic energy that maintains ocean circulation cascades down to small scales until it is dissipated through mixing. While most steps of this downward energy cascade are well understood, an observational gap exists at horizontal scales of 103–101 m that prevents characterizing a key step in the chain: the transition from anisotropic internal wave motions to isotropic turbulence. Here we show that this observational gap can be covered using high‐resolution multichannel seismic (HR‐MCS) data. Spectral analysis of acoustic reflectors imaged in the Alboran Sea thermocline shows that this transition is likely caused by shear instabilities. In particular, we show that the averaged horizontal wave number spectra of the reflectors vertical displacements display three subranges that reproduce theoretical spectral slopes of internal waves (λx > 100 m), Kelvin‐Helmholtz‐type shear instabilities (100 m > λx > 33 m), and turbulence (λx < 33 m), indicating that the whole chain of events is occurring continuously and simultaneously in the surveyed area.

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Observations of internal waves and associated mixing phenomena in the Portimao Canyon area

Cited by 31 publications

References 16 publications

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

Controlling factors of volumetrically important marine carbonate cementation in deep slope settings

A review of the role of submarine canyons in deep-ocean exchange with the shelf

Characterization of the submesoscale energy cascade in the Alboran Sea thermocline from spectral analysis of high‐resolution MCS data

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