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S. R. Rintoul - One of the best experts on this subject based on the ideXlab platform.
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Hydrothermal Heat Enhances Abyssal Mixing in the Antarctic Circumpolar Current
Geophysical Research Letters, 2019Co-Authors: Stephanie M. Downes, S. R. Rintoul, Bernadette M. Sloyan, John E. LuptonAbstract:Upwelling in the world's strongest Current, the Antarctic Circumpolar Current, is thought to be driven by wind stress, surface buoyancy flux, and mixing generated from the interaction between bottom Currents and rough topography. However, the impact of localized injection of heat by hydrothermal vents where the Antarctic Circumpolar Current interacts with mid-ocean ridges remains poorly understood. Here a Circumpolar compilation of helium and physical measurements are used to show that while geothermal heat is transferred to the ocean over a broad area by conduction, heat transfer by convection dominates near hydrothermal vents. Buoyant hydrothermal plumes decrease stratification above the vent source and increase stratification to the south, altering the local vertical diffusivity and diapycnal upwelling within 500 m of the sea floor by an order of magnitude. Both the helium tracer and stratification signals induced by hydrothermal input are advected by the flow and influence properties downstream.
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antarctic Circumpolar Current transport and barotropic transition at macquarie ridge
Geophysical Research Letters, 2014Co-Authors: S. R. Rintoul, Serguei Sokolov, M J M Williams, Pena B Molino, Mark Rosenberg, N L BindoffAbstract:Theory and numerical simulations suggest that topographic interactions are central to the dynamics of the Antarctic Circumpolar Current (ACC), but few observations are available to test these ideas. We use direct velocity measurements, satellite altimetry, and an ocean state estimate to investigate the interaction of the ACC with the Macquarie Ridge. Satellite altimeter data show that the Subantarctic Front crosses the ridge through a gap immediately north of Macquarie Island. Yearlong Current meter records reveal strong deep mean flow (> 0.2 m s−1 at 3000 m) and substantial transport (52 ± 8 × 106 m3 s−1) in the 50 km wide gap. The ACC becomes much more barotropic at the ridge. Acceleration of the deep jet is balanced by the ageostrophic along-gap pressure gradient, convergence of zonal momentum by the mean vertical velocity, and dissipation. The study helps explain how the ACC negotiates large topographic obstacles and highlights the role of local, nonlinear processes in the dynamical balance of the ACC.
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Antarctic Circumpolar Current
Encyclopedia of Ocean Sciences, 2009Co-Authors: S. R. RintoulAbstract:The Antarctic Circumpolar Current (ACC) is the largest Current in the world ocean, carrying about 137±8×106 m3 s−1 from west to east around Antarctica. By connecting the ocean basins, the ACC allows water masses and climate anomalies to propagate between the basins. The Current flow is concentrated in a number of Circumpolar fronts, which extend from the sea surface to the seafloor. The fronts also mark the boundaries between zones with distinct physical, chemical, and ecological characteristics. Eddies produced by dynamical instabilities of the fronts play an important part in the dynamics of the ACC by transporting momentum vertically and heat and mass poleward. Both wind and buoyancy forcing contribute to driving the ACC. Interaction between the deep-reaching flow and the bottom topography establish bottom form stresses to balance the wind forcing. The strong eastward flow of the ACC is intimately connected to an overturning circulation made up of two counter-rotating cells. Water mass transformations driven by exchange of heat and moisture with the atmosphere connect the upper and lower limbs of the thermohaline circulation. The transport and storage of heat, freshwater, and carbon dioxide by the ACC has a significant influence on global and regional climate.
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The response of the Antarctic Circumpolar Current to recent climate change
Nature Geoscience, 2008Co-Authors: C. W. Böning, A. Dispert, M. Visbeck, S. R. Rintoul, F. U. SchwarzkopfAbstract:Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30^∘ and 60^∘ S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress. The response of ocean circulation in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. An analysis of Argo data and historical measurements suggests that transport in the Antarctic Circumpolar Current and the meridional overturning circulation in the Southern Ocean are insensitive to decadal changes in wind stress.
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The response of the Antarctic Circumpolar Current to recent climate change
Nature Geoscience, 2008Co-Authors: C. W. Böning, A. Dispert, M. Visbeck, S. R. Rintoul, F. U. SchwarzkopfAbstract:Observations show a significant intensification of the Southern Hemisphere westerlies, the prevailing winds between the latitudes of 30° and 60° S, over the past decades. A continuation of this intensification trend is projected by climate scenarios for the twenty-first century. The response of the Antarctic Circumpolar Current and the carbon sink in the Southern Ocean to changes in wind stress and surface buoyancy fluxes is under debate. Here we analyse the Argo network of profiling floats and historical oceanographic data to detect coherent hemispheric-scale warming and freshening trends that extend to depths of more than 1,000 m. The warming and freshening is partly related to changes in the properties of the water masses that make up the Antarctic Circumpolar Current, which are consistent with the anthropogenic changes in heat and freshwater fluxes suggested by climate models. However, we detect no increase in the tilt of the surfaces of equal density across the Antarctic Circumpolar Current, in contrast to coarse-resolution model studies. Our results imply that the transport in the Antarctic Circumpolar Current and meridional overturning in the Southern Ocean are insensitive to decadal changes in wind stress.
Paul E Robbins - One of the best experts on this subject based on the ideXlab platform.
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comments on on the obscurantist physics of form drag in theorizing about the Circumpolar Current authors reply
Journal of Physical Oceanography, 1997Co-Authors: C W Hughes, Bruce A Warren, J H Lacasce, Paul E RobbinsAbstract:In a recent note, Warren et al. presented the opinion that considerations of form drag in the dynamics of the Antarctic Circumpolar Current (ACC) are obscurantist in nature and a distraction from the more promising Sverdrup approach to ACC dynamics. I would argue that, on the contrary, the concept of form drag is one of several important considerations in understanding ACC dynamics and is the one that most clearly distinguishes the ACC from midocean gyres.
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on the obscurantist physics of form drag in theorizing about the Circumpolar Current
Journal of Physical Oceanography, 1996Co-Authors: Bruce A Warren, J H Lacasce, Paul E RobbinsAbstract:Abstract The authors point out that, since the “form-drag” force balance commonly advanced for the Antarctic Circumpolar Current is really just a statement that northward Ekman transport in the Circumpolar Drake Passage zone is compensated by deep southward geostrophic flow, the balance is actually irrelevant to the magnitude of the Current itself. It is thus misleading to ascribe a role to form drag in its physics. Sverdrup dynamics seems to offer a more promising analysis of the real Circumpolar Current–as proposed long ago.
Alberto C. Naveira Garabato - One of the best experts on this subject based on the ideXlab platform.
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Topographic Control of Southern Ocean Gyres and the Antarctic Circumpolar Current: A Barotropic Perspective
Journal of Physical Oceanography, 2019Co-Authors: Ryan Declan Patmore, Paul R. Holland, David R. Munday, Alberto C. Naveira Garabato, David P. Stevens, Michael P. MeredithAbstract:AbstractIn the Southern Ocean the Antarctic Circumpolar Current is significantly steered by large topographic features, and subpolar gyres form in their lee. The geometry of topographic features in...
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Internal waves and turbulence in the Antarctic Circumpolar Current
Journal of Physical Oceanography, 2013Co-Authors: Stephanie Waterman, Alberto C. Naveira Garabato, Kurt L. PolzinAbstract:AbstractThis study reports on observations of turbulent dissipation and internal wave-scale flow properties in a standing meander of the Antarctic Circumpolar Current (ACC) north of the Kerguelen Plateau. The authors characterize the intensity and spatial distribution of the observed turbulent dissipation and the derived turbulent mixing, and consider underpinning mechanisms in the context of the internal wave field and the processes governing the waves’ generation and evolution.The turbulent dissipation rate and the derived diapycnal diffusivity are highly variable with systematic depth dependence. The dissipation rate is generally enhanced in the upper 1000–1500 m of the water column, and both the dissipation rate and diapycnal diffusivity are enhanced in some places near the seafloor, commonly in regions of rough topography and in the vicinity of strong bottom flows associated with the ACC jets. Turbulent dissipation is high in regions where internal wave energy is high, consistent with the idea that i...
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling^ 1 , 2 , as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean^ 3 , 4 , 5 , 6 , 7 , 8 . Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage^ 9 —to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning^ 4 , 5 , 6 , 7 , 8 . These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current.
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling1,2, as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean3,4,5,6,7,8. Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage9—to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning4,5,6,7,8. These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
Wolfgang Roether - One of the best experts on this subject based on the ideXlab platform.
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling^ 1 , 2 , as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean^ 3 , 4 , 5 , 6 , 7 , 8 . Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage^ 9 —to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning^ 4 , 5 , 6 , 7 , 8 . These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current.
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling1,2, as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean3,4,5,6,7,8. Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage9—to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning4,5,6,7,8. These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
David P. Stevens - One of the best experts on this subject based on the ideXlab platform.
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Topographic Control of Southern Ocean Gyres and the Antarctic Circumpolar Current: A Barotropic Perspective
Journal of Physical Oceanography, 2019Co-Authors: Ryan Declan Patmore, Paul R. Holland, David R. Munday, Alberto C. Naveira Garabato, David P. Stevens, Michael P. MeredithAbstract:AbstractIn the Southern Ocean the Antarctic Circumpolar Current is significantly steered by large topographic features, and subpolar gyres form in their lee. The geometry of topographic features in...
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling^ 1 , 2 , as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean^ 3 , 4 , 5 , 6 , 7 , 8 . Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage^ 9 —to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning^ 4 , 5 , 6 , 7 , 8 . These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
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Short-circuiting of the overturning circulation in the Antarctic Circumpolar Current.
Nature, 2007Co-Authors: Alberto C. Naveira Garabato, David P. Stevens, Andrew J. Watson, Wolfgang RoetherAbstract:Ocean mixing in the Current that flows around Antarctica plays a key role in global ocean circulation, as it influences the rate at which water sinking to the deep ocean at high latitudes returns to the surface in the Southern Ocean. But the rates of mixing in the Antarctic Circumpolar Current, and the extent of upwelling induced, remain poorly understood due to a lack of direct observations. A natural phenomenon, the release of helium from submarine volcanoes into the Current near Drake Passage, provided an opportunity to fill in that observational gap. This natural tracer release experiment made it possible to measure both mixing and upwelling in the southwest Atlantic sector of the Current, and the results indicate that the rough topography of the ocean floor there leads to rapid mixing across density surfaces and rapid upwelling along density surfaces. This creates a previously unrecognized 'short circuit' in the global oceanic overturning circulation, allowing cold waters sinking to the ocean abyss to return to the surface more rapidly than was expected. A natural tracer-release experiment (an injection of helium by submarine volcanoes into the Current that flows around Antarctica) is used to measure the rates of mixing and upwelling in the southwest Atlantic sector of the Current. Results indicate that the rough topography of the ocean floor in this region leads to both rapid mixing across density surfaces and rapid upwelling along density surfaces, which together create a 'short circuit' in the global oceanic overturning circulation. The oceanic overturning circulation has a central role in the Earth’s climate system and in biogeochemical cycling1,2, as it transports heat, carbon and nutrients around the globe and regulates their storage in the deep ocean. Mixing processes in the Antarctic Circumpolar Current are key to this circulation, because they control the rate at which water sinking at high latitudes returns to the surface in the Southern Ocean3,4,5,6,7,8. Yet estimates of the rates of these processes and of the upwelling that they induce are poorly constrained by observations. Here we take advantage of a natural tracer-release experiment—an injection of mantle helium from hydrothermal vents into the Circumpolar Current near Drake Passage9—to measure the rates of mixing and upwelling in the Current’s intermediate layers over a sector that spans nearly one-tenth of its Circumpolar path. Dispersion of the tracer reveals rapid upwelling along density surfaces and intense mixing across density surfaces, both occurring at rates that are an order of magnitude greater than rates implicit in models of the average Southern Ocean overturning4,5,6,7,8. These findings support the view that deep-water pathways along and across density surfaces intensify and intertwine as the Antarctic Circumpolar Current flows over complex ocean-floor topography, giving rise to a short circuit of the overturning circulation in these regions.
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The Dynamics of the Antarctic Circumpolar Current
Journal of Physical Oceanography, 1996Co-Authors: Vladimir O. Ivchenko, Kelvin J. Richards, David P. StevensAbstract:Abstract The dynamics of the Antarctic Circumpolar Current (ACC) in a near-eddy-resolving model of the Southern Ocean (FRAM) are investigated. A streamwise coordinate system is used, rather than a more conventional approach of considering zonally averaged quantities. The motivation for this approach is the large deviation from a purely zonal flow made by the Current. Comparisons are made with a zonal-mean analysis of the same model. It is found that the topographic form drag is the main sink of the momentum that is input by the wind. However, in contrast to a zonal-mean analysis other terms, namely, horizontal mixing, bottom friction, and advection of momentum, are no longer negligible. The total effect of transient eddies is to produce a drag on the mean flow, again in contrast to the zonally averaged case. The vertical penetration of stress is considered. A generalized formula is derived for the interfacial form stress averaged along a convoluted path and that includes nonquasigeostrophic effects. The i...