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.

Dissolved Oxygen, NO and PO as tracers for Ross Sea Ice Shelf Water overflow

2003 ◽  
Vol 15 (3) ◽  
pp. 399-404 ◽  
Author(s):  
P. RIVARO ◽  
R. FRACHE ◽  
A. BERGAMASCO ◽  
R. HOHMANN
Keyword(s):  
Dissolved Oxygen ◽  
Ross Sea ◽  
Deep Ocean ◽  
Shelf Break ◽  
Shelf Water ◽  
Ice Shelf ◽  
Mixing Processes ◽  
Chemical Tracers ◽  
Shelf Slope ◽  
Ice Shelf Water

A mesoscale experiment was conducted in the Ross Sea near the shelf break in summer 1997–98 within the framework of the activities of the CLIMA Project of the Italian National Program for Antarctic Research (PNRA), focus on study the shelf—slope interaction between the shelf waters and the CDW in correspondence of the Antarctic Slope Front. This paper deals with the dissolved oxygen distribution and with the application of conservative tracers NO and PO related to the physical variables, improving understanding of mixing processes study in correspondence of the shelf break. Experimental data showed the presence of both Ice Shelf Water overflowing the shelf and Circumpolar Deep Water intruding onto the shelf. Dissolved Oxygen (DO), NO and PO resulted useful as chemical tracers in outlining the mixing processes and bottom water formation spreading off continental shelf break of the Ross Sea, in which seems to be evidence that ISW plays an important role. In fact, a plume of ISW was observed flowing down the continental slope to the deep ocean. From chemical tracers we estimate its magnitude to be about 0.4 ± 0.2 Sv.

scholarly journals Isohaline Salinity Budget of the North Atlantic Salinity Maximum

2015 ◽  
Vol 45 (3) ◽  
pp. 724-736 ◽  
Author(s):  
Frank Bryan ◽  
Scott Bachman
Keyword(s):  
North Atlantic ◽  
Water Mass ◽  
Mesoscale Eddies ◽  
Surface Fluxes ◽  
Small Scale ◽  
Mixing Processes ◽  
The North ◽  
The North Atlantic ◽  
Averaged Model

AbstractIn this study, the salinity budget of the North Atlantic subtropical salinity maximum region for control volumes bounded by isohaline surfaces is analyzed. The authors provide closed budgets based on output from a high-resolution numerical simulation and partial budgets based on analyses of observational climatologies of hydrography and surface fluxes. With this choice of control volume, advection is eliminated from the instantaneous volume-integrated salt budget, and time-mean advection is eliminated from the budget evaluated from time-averaged data. In this way, the role of irreversible mixing processes in the maintenance and variability of the salinity maximum are more readily revealed. By carrying out the analysis with both near-instantaneous and time-averaged model output, the role of mesoscale eddies in stirring and mixing for this water mass is determined. This study finds that the small-scale mixing acting on enhanced gradients generated by the mesoscale eddies is approximately equal to that acting on the large-scale gradients estimated from climatological-mean conditions. The isohaline salinity budget can be related to water mass transformation rates associated with surface forcing and mixing processes in a straightforward manner. The authors find that the surface net evaporation in the North Atlantic salinity maximum region accounts for a transformation of 7 Sverdrups (Sv; 1 Sv ≡ 106 m3 s−1) of water across the 37-psu isohaline outcrop into the salinity maximum in the simulation, whereas the estimate based on climatological observations is 9 to 10 Sv.

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 Role of Near-Inertial Internal Waves in Subthermocline Diapycnal Mixing in the Northern Gulf of Mexico

2015 ◽  
Vol 45 (12) ◽  
pp. 3137-3154 ◽  
Author(s):  
Zhao Jing ◽  
Ping Chang ◽  
Steven F. DiMarco ◽  
Lixin Wu
Keyword(s):  
Gulf Of Mexico ◽  
Hurricane Katrina ◽  
Internal Waves ◽  
Dominant Role ◽  
Deep Ocean ◽  
Diapycnal Mixing ◽  
Northern Gulf Of Mexico ◽  
Weather Patterns ◽  
The Impact

AbstractMoored ADCP data collected in the northern Gulf of Mexico are analyzed to examine near-inertial internal waves and their contribution to subthermocline diapycnal mixing based on a finescale parameterization of deep ocean mixing. The focus of the study is on the impact of near-inertial internal waves generated by an extreme weather event—that is, Hurricane Katrina—and by month-to-month variation in weather patterns on the diapycnal mixing. The inferred subthermocline diapycnal mixing exhibits pronounced elevation in the wake of Katrina. Both the increased near-inertial (0.8–1.8f, where f is the Coriolis frequency) and superinertial (>1.8f) shear variances contribute to the elevated diapycnal mixing, but the former plays a more dominant role. The intense wind work on near-inertial motions by the hurricane is largely responsible for the energetic near-inertial shear variance. Energy transfer from near-inertial to superinertial internal waves, however, appears to play an important role in elevating the superinertial shear variance. The inferred subthermocline diapycnal mixing in the region also exhibits significant month-to-month variation with the estimated diffusivity in January 2006 about 3 times the values in November and December 2005. The subseasonal change in the diapycnal mixing mainly results from the subseasonal variation of the near-inertial wind work that causes intensification of the near-inertial shear in January 2006.

scholarly journals Deep-sea turbulence evolution observed by multiple closely spaced instruments

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chu-Fang Yang ◽  
Wu-Cheng Chi ◽  
Hans van Haren
Keyword(s):  
Kinetic Energy ◽  
Internal Waves ◽  
Deep Sea ◽  
Large Scale ◽  
Time Derivative ◽  
Deep Ocean ◽  
Energy Dissipation Rate ◽  
Small Scale ◽  
Ocean Bottom ◽  
Seafloor Topography

AbstractTurbulent mixing in the deep ocean is not well understood. The breaking of internal waves on sloped seafloor topography can generate deep-sea turbulence. However, it is difficult to measure turbulence comprehensively due to its multi-scale processes, in addition to flow–flow and flow–topography interactions. Dense, high-resolution spatiotemporal coverage of observations may help shed light on turbulence evolution. Here, we present turbulence observations from four broadband ocean bottom seismometers (OBSs) and a 200-m vertical thermistor string (T-string) in a footprint of 1 × 1 km to characterize turbulence induced by internal waves at a depth of 3000 m on a Pacific continental slope. Correlating the OBS-calculated time derivative of kinetic energy and the T-string-calculated turbulent kinetic energy dissipation rate, we propose that the OBS-detected signals were induced by near-seafloor turbulence. Strong disturbances were detected during a typhoon period, suggesting large-scale inertial waves breaking with upslope transport speeds of 0.2–0.5 m s−1. Disturbances were mostly excited on the downslope side of the array where the internal waves from the Pacific Ocean broke initially and the turbulence oscillated between < 1 km small-scale ridges. Such small-scale topography caused varying turbulence-induced signals due to localized waves breaking. Arrayed OBSs can provide complementary observations to characterize deep-sea turbulence.

scholarly journals Shelf Flows Forced by Deep-Ocean Anticyclonic Eddies at the Shelf Break

2018 ◽  
Vol 48 (5) ◽  
pp. 1117-1138 ◽  
Author(s):  
Deepak A. Cherian ◽  
K. H. Brink
Keyword(s):  
Vertical Structure ◽  
Water Flux ◽  
Deep Ocean ◽  
Shelf Break ◽  
Western Boundary ◽  
Shelf Water ◽  
Wave Direction ◽  
Continental Shelves ◽  
Flow Features ◽  
Anticyclonic Eddies

AbstractIsolated monopolar eddies in the ocean tend to move westward. Those shed by western boundary currents may then interact with the continental margin. This simple picture is complicated by the presence of other flow features, but satellite observations show that many western boundary continental shelves experience cross-shelfbreak exchange flows forced by mesoscale eddies translating near the shelf break. Here we extend our previous study of eddy interaction with a flat shelf to that with a sloping shelf. Using a set of primitive equation numerical simulations, we address the vertical structure of the onshore and offshore flows forced by the eddy, the origin of the exported shelf water, and the extent to which eddy water can penetrate onto the shelf. The simulations reveal an asymmetry in the vertical structure of cross-shelfbreak flows: the offshore flow is generally barotropic, whereas the onshore flow is always baroclinic. The exported shelf water is sourced from downstream of the eddy in the coastal-trapped wave direction and is supplied by a barotropic alongshore jet. This “supply jet” has a Rhines-like cross-shore length scale proportional to (eddy velocity scale/shelf topographic beta)1/2 measured from the shelf break. Eddy water is forced onto the shelf and is present up to a distance of one internal Rossby deformation radius, defined using shelf properties, from the shelf break. We rationalize these horizontal and vertical scales, connect them to existing observations, and extend our previous parameterization of eddy-forced offshore shelf-water flux to account for nonzero shelf slopes.

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