The Experts below are selected from a list of 3189 Experts worldwide ranked by ideXlab platform
Faming Wang - One of the best experts on this subject based on the ideXlab platform.
-
direct evidence of an oceanic inverse kinetic energy cascade from satellite altimetry
2005Co-Authors: Robert B. Scott, Faming WangAbstract:Abstract Sea surface height measurements from satellites reveal the turbulent properties of the South Pacific Ocean surface geostrophic circulation, both supporting and challenging different aspects of geostrophic turbulence theory. A near-universal shape of the spectral kinetic energy flux is found and provides direct evidence of a source of kinetic energy near to or smaller than the deformation radius, consistent with linear instability theory. The spectral kinetic energy flux also reveals a net inverse cascade (i.e., a cascade to larger spatial scale), consistent with two-dimensional turbulence phenomenology. However, stratified geostrophic turbulence theory predicts an inverse cascade for the Barotropic Mode only; energy in the large-scale baroclinic Modes undergoes a direct cascade toward the first-Mode deformation scale. Thus if the surface geostrophic flow is predominately the first baroclinic Mode, as expected for oceanic stratification profiles, then the observed inverse cascade contradicts geost...
-
direct evidence of an oceanic inverse kinetic energy cascade from satellite altimetry
2005Co-Authors: Robert B. Scott, Faming WangAbstract:Sea surface height measurements from satellites reveal the turbulent properties of the South Pacific Ocean surface geostrophic circulation, both supporting and challenging different aspects of geostrophic turbulence theory. A near-universal shape of the spectral kinetic energy flux is found and provides direct evidence of a source of kinetic energy near to or smaller than the deformation radius, consistent with linear instability theory. The spectral kinetic energy flux also reveals a net inverse cascade (i.e., a cascade to larger spatial scale), consistent with two-dimensional turbulence phenomenology. However, stratified geostrophic turbulence theory predicts an inverse cascade for the Barotropic Mode only; energy in the large-scale baroclinic Modes undergoes a direct cascade toward the first-Mode deformation scale. Thus if the surface geostrophic flow is predominately the first baroclinic Mode, as expected for oceanic stratification profiles, then the observed inverse cascade contradicts geostrophic turbulence theory. The latter interpretation is argued for. Furthermore, and consistent with this interpretation, the inverse cascade arrest scale does not follow the Rhines arrest scale, as one would expect for the Barotropic Mode. A tentative revision of theory is proposed that would resolve the conflicts; however, further observations and idealized Modeling experiments are needed to confirm, or refute, the revision. It is noted that no inertial range was found for the inverse cascade range of the spectrum, implying inertial range scaling, such as the established K 5/3 slope in the spectral kinetic energy density plot, is not applicable to the surface geostrophic flow.
Robert B. Scott - One of the best experts on this subject based on the ideXlab platform.
-
direct evidence of an oceanic inverse kinetic energy cascade from satellite altimetry
2005Co-Authors: Robert B. Scott, Faming WangAbstract:Abstract Sea surface height measurements from satellites reveal the turbulent properties of the South Pacific Ocean surface geostrophic circulation, both supporting and challenging different aspects of geostrophic turbulence theory. A near-universal shape of the spectral kinetic energy flux is found and provides direct evidence of a source of kinetic energy near to or smaller than the deformation radius, consistent with linear instability theory. The spectral kinetic energy flux also reveals a net inverse cascade (i.e., a cascade to larger spatial scale), consistent with two-dimensional turbulence phenomenology. However, stratified geostrophic turbulence theory predicts an inverse cascade for the Barotropic Mode only; energy in the large-scale baroclinic Modes undergoes a direct cascade toward the first-Mode deformation scale. Thus if the surface geostrophic flow is predominately the first baroclinic Mode, as expected for oceanic stratification profiles, then the observed inverse cascade contradicts geost...
-
direct evidence of an oceanic inverse kinetic energy cascade from satellite altimetry
2005Co-Authors: Robert B. Scott, Faming WangAbstract:Sea surface height measurements from satellites reveal the turbulent properties of the South Pacific Ocean surface geostrophic circulation, both supporting and challenging different aspects of geostrophic turbulence theory. A near-universal shape of the spectral kinetic energy flux is found and provides direct evidence of a source of kinetic energy near to or smaller than the deformation radius, consistent with linear instability theory. The spectral kinetic energy flux also reveals a net inverse cascade (i.e., a cascade to larger spatial scale), consistent with two-dimensional turbulence phenomenology. However, stratified geostrophic turbulence theory predicts an inverse cascade for the Barotropic Mode only; energy in the large-scale baroclinic Modes undergoes a direct cascade toward the first-Mode deformation scale. Thus if the surface geostrophic flow is predominately the first baroclinic Mode, as expected for oceanic stratification profiles, then the observed inverse cascade contradicts geostrophic turbulence theory. The latter interpretation is argued for. Furthermore, and consistent with this interpretation, the inverse cascade arrest scale does not follow the Rhines arrest scale, as one would expect for the Barotropic Mode. A tentative revision of theory is proposed that would resolve the conflicts; however, further observations and idealized Modeling experiments are needed to confirm, or refute, the revision. It is noted that no inertial range was found for the inverse cascade range of the spectrum, implying inertial range scaling, such as the established K 5/3 slope in the spectral kinetic energy density plot, is not applicable to the surface geostrophic flow.
Christopher Eldred - One of the best experts on this subject based on the ideXlab platform.
-
Stability analysis of split-explicit free surface ocean Models: implication of the depth-independent Barotropic Mode approximation
2019Co-Authors: Jérémie Demange, Laurent Debreu, Patrick Marchesiello, Florian Lemarié, Eric Blayo, Christopher EldredAbstract:The evolution of the oceanic free-surface is responsible for the propagation of fast surface gravity waves, which approximatively propagate at speed $\sqrt{gH}$ (with $g$ the gravity and $H$ the local water depth). In the deep ocean, this phase speed is roughly two orders of magnitude faster than the fastest internal gravity waves. The very strong stability constraint imposed by those fast surface waves on the time-step of numerical Models is handled using a Mode splitting between slow (internal/baroclinic) and fast (external/Barotropic) motions to allow the possibility to adopt specific numerical treatments in each component. The Barotropic Mode is traditionally approximated by the vertically integrated flow because it has only slight vertical variations. However the implications of this assumption on the stability of the splitting are not well documented. In this paper, we describe a stability analysis of the Mode splitting technique based on an eigenvector decomposition using the true (depth-dependent) Barotropic Mode. This allows us to quantify the amount of dissipation required to stabilize the approximative splitting. We show that, to achieve stable integrations, the dissipation usually applied through averaging filters can be drastically reduced when incorporated at the level of the Barotropic time stepping. The benefits are illustrated by numerical experiments. In addition, the formulation of a new Mode splitting algorithm using the depth-dependent Barotropic Mode is introduced.
Georgy E. Manucharyan - One of the best experts on this subject based on the ideXlab platform.
-
Partitioning of Kinetic Energy in the Arctic Ocean's Beaufort Gyre
2018Co-Authors: Mengnan Zhao, Mary-louise Timmermans, Richard A. Krishfield, Georgy E. ManucharyanAbstract:Kinetic energy (KE) in the Arctic Ocean's Beaufort Gyre is dominated by the mesoscale eddy field that plays a central role in the transport of freshwater, heat, and biogeochemical tracers. Understanding Beaufort Gyre KE variability sheds light on how this freshwater reservoir responds to wind forcing and sea ice and ocean changes. The evolution and fate of mesoscale eddies relate to energy pathways in the ocean (e.g., the exchange of energy between Barotropic and baroclinic Modes). Mooring measurements of horizontal velocities in the Beaufort Gyre are analyzed to partition KE into Barotropic and baroclinic Modes and explore their evolution. We find that a significant fraction of water column KE is in the Barotropic and the first two baroclinic Modes. We explain this energy partitioning by quantifying the energy transfer coefficients between the vertical Modes using the quasi‐geostrophic potential vorticity conservation equations with a specific background stratification observed in the Beaufort Gyre. We find that the quasi‐geostrophic vertical Mode interactions uphold the persistence of KE in the first two baroclinic Modes, consistent with observations. Our results explain the specific role of halocline structure on KE evolution in the gyre and suggest depressed transfer to the Barotropic Mode. This limits the capacity for frictional dissipation at the sea floor and suggests that energy dissipation via sea ice‐ocean drag may be prominent.
Wilbert Weijer - One of the best experts on this subject based on the ideXlab platform.
-
Here for Full Article An almost‐free Barotropic Mode in the Australian‐Antarctic Basin
2016Co-Authors: Wilbert WeijerAbstract:[1] The Australian‐Antarctic Basin (AAB) is known for its high levels of intraseasonal variability; sea‐surface height variability exceeds background values by factors of 2 over thousands of kilometers. This paper addresses the hypothesis that this variability is caused by trapping of Barotropic energy by the basin geometry. Analysis of a multi‐year integration of a shallow‐water Model shows that the variability is dominated by a single, large‐scale statistical Mode that is highly coherent over the entire AAB. The flow associated with this Mode is northwestward along the Southeast Indian Ridge, southward in the Kerguelen Abyssal Plain, and eastward in the southern AAB. The Mode is interpreted as an almost‐free topographically trapped Mode, as it is confined by contours of potential vorticity that almost entirely enclose the AAB. The apex of the Wilkes Abyssal Plain represents the strongest barrier to the modal circulation: here velocities are strongest, making it a key area for dissipation of kinetic energy through bottom friction and eddy viscosity. Citation: Weijer, W. (2010), An almost‐free Barotropic Mode in the Australian‐Antarctic Basin, Geophys. Res. Le t t., 37, L10602, doi:10.1029
-
an almost free Barotropic Mode in the australian antarctic basin
2010Co-Authors: Wilbert WeijerAbstract:[1] The Australian-Antarctic Basin (AAB) is known for its high levels of intraseasonal variability; sea-surface height variability exceeds background values by factors of 2 over thousands of kilometers. This paper addresses the hypothesis that this variability is caused by trapping of Barotropic energy by the basin geometry. Analysis of a multi-year integration of a shallow-water Model shows that the variability is dominated by a single, large-scale statistical Mode that is highly coherent over the entire AAB. The flow associated with this Mode is northwestward along the Southeast Indian Ridge, southward in the Kerguelen Abyssal Plain, and eastward in the southern AAB. The Mode is interpreted as an almost-free topographically trapped Mode, as it is confined by contours of potential vorticity that almost entirely enclose the AAB. The apex of the Wilkes Abyssal Plain represents the strongest barrier to the modal circulation: here velocities are strongest, making it a key area for dissipation of kinetic energy through bottom friction and eddy viscosity.