scholarly journals Tidal mixing processes amid small-scale, deep-ocean topography

2015 ◽  
Vol 42 (2) ◽  
pp. 484-491 ◽  
Author(s):  
Andrew C. Dale ◽  
Mark E. Inall
Keyword(s):  
Deep Ocean ◽  
Tidal Mixing ◽  
Small Scale ◽  
Mixing Processes ◽  
Ocean Topography

scholarly journals Construction of a 3D Mooring Array of Temperature Sensors

2016 ◽  
Vol 33 (10) ◽  
pp. 2247-2257 ◽  
Author(s):  
Hans van Haren ◽  
Johan van Heerwaarden ◽  
Roel Bakker ◽  
Martin Laan
Keyword(s):  
Deep Ocean ◽  
Free Fall ◽  
Temperature Sensors ◽  
Small Scale ◽  
Quantitative Studies ◽  
Diameter Structure ◽  
Inner Diameter ◽  
Ocean Topography ◽  
Free Falling ◽  
Better Than

AbstractA small-scale 3D mooring array comprising up to 550 high-resolution temperature sensors was custom designed and constructed. The stand-alone array samples ocean temperature to depths of about 3000 m, limited by the buoyancy elements, at a rate of 1 Hz, with a precision better than 0.5 mK, a noise level better than 0.1 mK, and an endurance of 1 year. Its purpose serves quantitative studies on the development of turbulent mixing by internal wave breaking above deep-ocean topography. The 3D array consists of five parallel cables 105 m long with 3.2 mm inner diameter during the first deployment, now 5.5 mm. The cables are 4 and 5.6 m apart horizontally and are held under tension of 1000 N each using heavy buoyancy elements in a single line above. The entire array is folded into a 6-m high, 3-m-diameter structure above a 750-kg weight. It is deployed in a single overboard operation similar to that of a free-falling mooring. New here is the unfolding of the compacted array when hanging overboard and prior to release into free fall.

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

Ocean Science ◽  
2009 ◽  
Vol 5 (4) ◽  
pp. 607-620 ◽  
Author(s):  
S. E. Allen ◽  
X. Durrieu de Madron
Keyword(s):  
Internal Waves ◽  
Deep Ocean ◽  
Shelf Break ◽  
Small Scale ◽  
Rossby Number ◽  
Shelf Water ◽  
Submarine Canyons ◽  
Mixing Processes ◽  
State Of The Science

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 shelf-water 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.

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

2009 ◽  
Vol 6 (2) ◽  
pp. 1369-1406 ◽  
Author(s):  
S. E. Allen ◽  
X. Durrieu de Madron
Keyword(s):  
Internal Waves ◽  
Deep Ocean ◽  
Shelf Break ◽  
Small Scale ◽  
Rossby Number ◽  
Shelf Water ◽  
Submarine Canyons ◽  
Mixing Processes ◽  
State Of The Science

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 shelf-water 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.

scholarly journals Physical Transport Processes that Affect the Distribution of Oil in the Gulf of Mexico: Observations and Modeling

Oceanography ◽  
2021 ◽  
Vol 34 (1) ◽  
pp. 58-75
Author(s):  
Michel Boufadel ◽  
◽  
Annalisa Bracco ◽  
Eric Chassignet ◽  
Shuyi Chen ◽  
...  
Keyword(s):  
Gulf Of Mexico ◽  
Physical Environment ◽  
Large Scale ◽  
Transport Processes ◽  
Small Scale ◽  
Surface Mixed Layer ◽  
Physical Processes ◽  
Mixing Processes ◽  
Near Surface ◽  
Wide Range

Physical transport processes such as the circulation and mixing of waters largely determine the spatial distribution of materials in the ocean. They also establish the physical environment within which biogeochemical and other processes transform materials, including naturally occurring nutrients and human-made contaminants that may sustain or harm the region’s living resources. Thus, understanding and modeling the transport and distribution of materials provides a crucial substrate for determining the effects of biological, geological, and chemical processes. The wide range of scales in which these physical processes operate includes microscale droplets and bubbles; small-scale turbulence in buoyant plumes and the near-surface “mixed” layer; submesoscale fronts, convergent and divergent flows, and small eddies; larger mesoscale quasi-geostrophic eddies; and the overall large-scale circulation of the Gulf of Mexico and its interaction with the Atlantic Ocean and the Caribbean Sea; along with air-sea interaction on longer timescales. The circulation and mixing processes that operate near the Gulf of Mexico coasts, where most human activities occur, are strongly affected by wind- and river-induced currents and are further modified by the area’s complex topography. Gulf of Mexico physical processes are also characterized by strong linkages between coastal/shelf and deeper offshore waters that determine connectivity to the basin’s interior. This physical connectivity influences the transport of materials among different coastal areas within the Gulf of Mexico and can extend to adjacent basins. Major advances enabled by the Gulf of Mexico Research Initiative in the observation, understanding, and modeling of all of these aspects of the Gulf’s physical environment are summarized in this article, and key priorities for future work are also identified.

3-D tomographic observations of Rossby wave breaking over the Northern Atlantic during the WISE aircraft campaign in 2017

2021 ◽  
Author(s):  
Lukas Krasauskas ◽  
Jörn Ungermann ◽  
Peter Preusse ◽  
Felix Friedl-Vallon ◽  
Andreas Zahn ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Water Vapour ◽  
Rossby Wave ◽  
Wave Breaking ◽  
Thin Filament ◽  
Small Scale ◽  
Data Sets ◽  
Mixing Processes ◽  
Air Masses ◽  
Rossby Wave Breaking

<p>We present measurements of ozone, water vapour and nitric acid in the upper troposphere/lower stratosphere (UTLS) over North Atlantic and Europe. The measurements were acquired with the Gimballed Limb Observer for Radiance Imaging of the Atmosphere (GLORIA) during the Wave Driven Isentropic Exchange (WISE) campaign in October 2017. GLORIA is an airborne limb imager capable of acquiring both 2-D data sets (curtains along the flight path) and, when the carrier aircraft is flying around the observed air mass, spatially highly resolved 3-D tomographic data. We show a case study of a Rossby wave (RW) breaking event observed during two subsequent flights two days apart. RW breaking is known to steepen tracer gradients and facilitate stratosphere-troposphere exchange (STE). Our measurements reveal complex spatial structures in stratospheric tracers (ozone and nitric acid) with multiple vertically stacked filaments. Backward trajectory analysis is used to demonstrate that these features are related to several previous Rossby wave breaking events and that the small-scale structure of the UTLS in the Rossby wave breaking region, which is otherwise very hard to observe, can be understood as stirring and mixing of air masses of tropospheric and stratospheric origin. It is also shown that a strong nitric acid enhancement observed just above the tropopause is likely a result of NO<sub>x</sub> production by lightning activity. The measurements showed signatures of enhanced mixing between stratospheric and tropospheric air near the polar jet with some transport of water vapour into the stratosphere. Some of the air masses seen in 3-D data were encountered again two days later, stretched to very thin filament (horizontal thickness down to 30 km at some altitudes) rich in stratospheric tracers. This repeated measurement allowed us to directly observe and analyse the progress of mixing processes in a thin filament over two days. Our results provide direct insight into small-scale dynamics of the UTLS in the Rossby wave breaking region, witch is of great importance to understanding STE and poleward transport in the UTLS.</p>

7. Tidal mixing

2019 ◽  
pp. 98-115
Author(s):  
David George Bowers ◽  
Emyr Martyn Roberts
Keyword(s):  
Water Depth ◽  
Deep Ocean ◽  
Tidal Currents ◽  
The Other ◽  
Tidal Mixing ◽  
Shelf Seas ◽  
Tidal Mixing Front ◽  
Tidal Streams

‘Tidal mixing’ describes tidal mixing in shelf seas, where the water is shallow and tidal currents can be much faster than in the deep ocean. Most of the energy lost from the tide through friction is first converted into turbulence, which then makes a very effective mixing mechanism, stirring the Sun’s heat downwards. Shelf seas at temperate latitudes in summer are divided into stratified regions and vertically mixed regions, depending on the tidal streams’ strength and the water depth. The transition from one to the other happens rapidly and creates a tidal mixing front. Tidal mixing in estuaries is also discussed along with the harnessing of tides to generate electricity.

scholarly journals An improved parameterization of tidal mixing for ocean models

2014 ◽  
Vol 7 (1) ◽  
pp. 211-224 ◽  
Author(s):  
A. Schmittner ◽  
G. D. Egbert
Keyword(s):  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Deep Ocean ◽  
Meridional Overturning Circulation ◽  
Tidal Mixing ◽  
Overturning Circulation ◽  
Microstructure Measurements ◽  
High Resolution Bathymetry ◽  
Diurnal Tides

Abstract. Two modifications to an existing scheme of tidal mixing are implemented in the coarse resolution ocean component of a global climate model. First, the vertical distribution of energy flux out of the barotropic tide is determined using high resolution bathymetry. This shifts the levels of mixing higher up in the water column and leads to a stronger mid-depth meridional overturning circulation in the model. Second, the local dissipation efficiency for diurnal tides is assumed to be larger than that for the semi-diurnal tides poleward of 30°. Both modifications are shown to improve agreement with observational estimates of diapycnal diffusivities based on microstructure measurements and circulation indices. We also assess impacts of different spatial distributions of the barotropic energy loss. Estimates based on satellite altimetry lead to larger diffusivities in the deep ocean and hence a stronger deep overturning circulation in our climate model that is in better agreement with observation based estimates compared to those based on a tidal model.

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