The Experts below are selected from a list of 9390 Experts worldwide ranked by ideXlab platform
Patrice Klein - One of the best experts on this subject based on the ideXlab platform.
-
Incoherent signature of internal tides on sea level in idealized numerical simulations
Geophysical Research Letters, 2015Co-Authors: Aurelien Ponte, Patrice KleinAbstract:The nonpersistent phase relationship between internal tides and astronomical forcings, also known as incoherence, has been identified as a major question in the context of future wide-swath satellite altimetry. This study addresses this issue using a novel set of numerical experiments where a plane wave/low-mode internal tide propagates through a turbulent Mesoscale Eddy field. These experiments demonstrate the emergence of internal tide incoherence as the Eddy turbulence is strengthened. In strongly turbulent situations, the internal tide signature on sea level forms complex interference patterns with large amplifications of the initial internal wave. These patterns evolve more rapidly than the signature of the turbulent Eddy field on sea level. The implications of such idealized numerical simulations for wide-swath altimetry are discussed.
-
propagation of wind energy into the deep ocean through a fully turbulent Mesoscale Eddy field
Journal of Physical Oceanography, 2008Co-Authors: Eric Danioux, Patrice Klein, Pascal RiviereAbstract:Abstract The authors analyze the 3D propagation of wind-forced near-inertial motions in a fully turbulent Mesoscale Eddy field with a primitive equation numerical model. Although the wind stress is uniform, the near-inertial motion field quickly becomes spatially heterogeneous, involving horizontal scales much smaller than the Eddy scales. Analysis confirms that refraction by the Eddy relative vorticity is the main mechanism responsible for the horizontal distortion of the near-inertial motions, which subsequently triggers their vertical propagation. An important result is the appearance of two maxima of near-inertial vertical velocity (both with rms values reaching 40 m day−1): one at a depth of 100 m and another unexpected one much below the main thermocline around 1700 m. The shallow maximum, captured by the highest vertical normal modes, involves near-inertial motions with a spatial heterogeneity close to the Eddy vorticity gradient field. These characteristics match analytical results obtained with Y...
-
Propagation of wind energy into the deep ocean through a fully turbulent Mesoscale Eddy field.
Journal of Physical Oceanography, 2008Co-Authors: Eric Danioux, Patrice Klein, Pascal RiviereAbstract:We analyse the 3-D propagation of wind-forced near-inertial motions in a fully turbulent Mesoscale Eddy field with a primitive-equation numerical model. Although the wind-stress is uniform, the near-inertial motion field quickly becomes spatially heterogeneous, involving horizontal scales much smaller than the Eddy scales. Analysis confirms that refraction by the Eddy relative vorticity is the main mechanism responsible for the horizontal distortion of the near-inertial motions, which subsequently triggers their vertical propagation. An important result is the appearance of two maxima of near-inertial vertical velocity (both with r.m.s. values reaching 40 m/day): one at a depth of 100 m and another unexpected one much below the main thermocline around 1700 m. The shallow maximum, captured by the highest vertical normal modes, involves near-inertial motions with a spatial heterogeneity close to the Eddy vorticity gradient field. These characteristics match analytical results obtained with Young and Ben Jelloul (1997)'s approach. The deep maximum, captured by the lowest vertical normal modes, involves superinertial motions with a frequency of twice the inertial frequency and much smaller horizontal scales. Because of these characteristics, not anticipated by previous analytical studies, these superinertial motions may represent an energy source for small-scale mixing through a mechanism not taken into account in the present study: the parametric subharmonic instability (PSI). This reveals a pathway by which wind energy may have a significant impact on small-scale mixing in the deep interior. Further studies that explicitly take into account PSI are needed to estimate this potential impact.
-
Organization of near-inertial energy by an Eddy field.
Quarterly Journal of the Royal Meteorological Society, 2004Co-Authors: Patrice Klein, Stefan Llewellyn Smith, Guillaume LapeyreAbstract:We propose an analytical solution for the evolution of the spatial variability of wind-forced inertial energy in the presence of an oceanic Mesoscale Eddy field. The solution requires knowledge of only the stream function of the Eddy field and the Rossby radii of the normal modes associated with the near-inertial oscillations. It also shows that, when the vorticity spectrum slope is shallower than k-4, inertial energy is trapped inside structures in which the Laplacian of the vorticity field is positive and whose size matches a critical length-scale that increases with time. Numerical simulations using different models, including a fully nonlinear shallow-water model, confirm the analytical results.
Kurt L. Polzin - One of the best experts on this subject based on the ideXlab platform.
-
Mesoscale Eddy–Internal Wave Coupling. Part II: Energetics and Results from PolyMode
Journal of Physical Oceanography, 2010Co-Authors: Kurt L. PolzinAbstract:The issue of internal wave‐Mesoscale Eddy interactions is revisited. Previous observational work identified the Mesoscale Eddy field as a possible source of internal wave energy. Characterization of the coupling as a viscous process provides a smaller horizontal transfer coefficient than previously obtained, with vh ffi 50 m 2 s 21 in contrast to nh ffi 200‐400 m 2 s 21 , and a vertical transfer coefficient bounded away from zero, with ny 1 ( f 2 /N 2 )Kh ffi 2.5 6 0.3 3 10 23 m 2 s 21 in contrast to ny 1 ( f 2 /N 2 )Kh 5 0 6 2 3 10 22 m 2 s 21 . Current meter data from the Local Dynamics Experiment of the PolyMode field program indicate Mesoscale Eddy‐ internal wave coupling through horizontal interactions (i) is a significant sink of Eddy energy and (ii) plays an O(1) role in the energy budget of the internal wave field.
-
Mesoscale Eddy internal wave coupling part ii energetics and results from polymode
Journal of Physical Oceanography, 2010Co-Authors: Kurt L. PolzinAbstract:The issue of internal wave‐Mesoscale Eddy interactions is revisited. Previous observational work identified the Mesoscale Eddy field as a possible source of internal wave energy. Characterization of the coupling as a viscous process provides a smaller horizontal transfer coefficient than previously obtained, with vh ffi 50 m 2 s 21 in contrast to nh ffi 200‐400 m 2 s 21 , and a vertical transfer coefficient bounded away from zero, with ny 1 ( f 2 /N 2 )Kh ffi 2.5 6 0.3 3 10 23 m 2 s 21 in contrast to ny 1 ( f 2 /N 2 )Kh 5 0 6 2 3 10 22 m 2 s 21 . Current meter data from the Local Dynamics Experiment of the PolyMode field program indicate Mesoscale Eddy‐ internal wave coupling through horizontal interactions (i) is a significant sink of Eddy energy and (ii) plays an O(1) role in the energy budget of the internal wave field.
James C Mcwilliams - One of the best experts on this subject based on the ideXlab platform.
-
a new sea surface height based code for oceanic Mesoscale Eddy tracking
Journal of Atmospheric and Oceanic Technology, 2014Co-Authors: Evan Mason, Ananda Pascual, James C McwilliamsAbstract:This paper presents a software tool thatenablesthe identification and automatedtracking ofoceanic eddies observed with satellite altimetry in user-specified regions throughout the global ocean. As input, the code requires sequential maps of sea level anomalies such as those provided by Archiving, Validation, and Interpretationof SatelliteOceanographic (AVISO) data. Outputstake the form of (i) datafiles containing Eddy properties,includingposition,radius,amplitude,andazimuthal(geostrophic)speed;and(ii) sequentialimage maps showingseasurface heightmaps withactive Eddycenters andtracksoverlaid.The resultsgivenare from a demonstration in the Canary Basin region of the northeast Atlantic and are comparable with a published global Eddy track database. Some discrepancies between the two datasets include Eddy radius magnitude, and the distributions of Eddy births and deaths. The discrepancies may be related to differences in the Eddy identification methods, and also possibly to differences in the smoothing of the sea surface height maps. The code is written in Python and is made freely available under a GNU license (http://www.imedea.uib.es/users/ emason/py-Eddy-tracker/).
-
Mesoscale Eddy buoyancy flux and Eddy induced circulation in eastern boundary currents
Journal of Physical Oceanography, 2013Co-Authors: Francois Colas, Xavier Capet, James C McwilliamsAbstract:AbstractA dynamical interpretation is made of the Mesoscale Eddy buoyancy fluxes in the Eastern Boundary Currents off California and Peru–Chile, based on regional equilibrium simulations. The Eddy fluxes are primarily shoreward and upward across a swath several hundred kilometers wide in the upper ocean; as such they serve to balance mean offshore air–sea heating and coastal upwelling. In the stratified interior the Eddy fluxes are consistent with the adiabatic hypothesis associated with a mean Eddy-induced velocity advecting mean buoyancy and tracers. Furthermore, with a suitable gauge choice, the horizontal fluxes are almost entirely aligned with the mean horizontal buoyancy gradient, consistent with the advective parameterization scheme of Gent and McWilliams. The associated diffusivity κ is surface intensified, matching the vertical stratification profile. The fluxes span the across-shore band of high Eddy energy, but their alongshore structure is unresolved because of sampling limitations. In the sur...
-
Mesoscale Eddy Buoyancy Flux and Eddy-Induced Circulation in Eastern Boundary Currents
Journal of Physical Oceanography, 2013Co-Authors: Francois Colas, Xavier Capet, James C McwilliamsAbstract:A dynamical interpretation is made of the Mesoscale Eddy buoyancy fluxes in the Eastern Boundary Currents off California and Peru-Chile, based on regional equilibrium simulations. The Eddy fluxes are primarily shoreward and upward across a swath several hundred kilometers wide in the upper ocean; as such they serve to balance mean offshore air-sea heating and coastal upwelling. In the stratified interior the Eddy fluxes are consistent with the adiabatic hypothesis associated with a mean Eddy-induced velocity advecting mean buoyancy and tracers. Furthermore, with a suitable gauge choice, the horizontal fluxes are almost entirely aligned with the mean horizontal buoyancy gradient, consistent with the advective parameterization scheme of Gent and McWilliams. The associated diffusivity κ is surface intensified, matching the vertical stratification profile. The fluxes span the across-shore band of high Eddy energy, but their alongshore structure is unresolved because of sampling limitations. In the surface layer the Eddy flux is significantly diabatic with a shallow Eddy-induced circulation cell and downgradient lateral diapycnal flux. The dominant Eddy generation process is baroclinic instability, but there are significant regional differences between the upwelling systems in the flux and κ that are not consistent with simple instability theory.
-
localization of deep ocean convection by a Mesoscale Eddy
Journal of Physical Oceanography, 1998Co-Authors: Sonya Legg, James C Mcwilliams, Jianbo GaoAbstract:Abstract Observations of open-ocean deep convection indicate that it is a highly localized phenomenon, occurring over areas of tens of kilometers in diameter. The cause of this localization has been ascribed to “preconditioning”—the local weakening of the stable density stratification associated with upwardly domed isopycnal surfaces in a surface-intensified cyclonic circulation. However, most numerical and laboratory studies of localized convection have prescribed the localization artificially, by confining the surface buoyancy loss to a circular disk. In contrast, in the numerical simulations described here, deep convection forced by horizontally uniform buoyancy loss is localized within a region of initially weaker stratification than its surroundings. The preconditioned region is associated with a cold-core cyclonic Eddy in geostrophic and cyclostrophic balance. As in previous studies of disk-shaped cooling, the localized convection region undergoes baroclinic instability at late times, causing the br...
Dudley B Chelton - One of the best experts on this subject based on the ideXlab platform.
-
satellite observations of Mesoscale Eddy induced ekman pumping
Journal of Physical Oceanography, 2015Co-Authors: Peter Gaube, Dudley B Chelton, R M Samelson, Michael G Schlax, Larry W OneillAbstract:AbstractThree mechanisms for self-induced Ekman pumping in the interiors of Mesoscale ocean eddies are investigated. The first arises from the surface stress that occurs because of differences between surface wind and ocean velocities, resulting in Ekman upwelling and downwelling in the cores of anticyclones and cyclones, respectively. The second mechanism arises from the interaction of the surface stress with the surface current vorticity gradient, resulting in dipoles of Ekman upwelling and downwelling. The third mechanism arises from Eddy-induced spatial variability of sea surface temperature (SST), which generates a curl of the stress and therefore Ekman pumping in regions of crosswind SST gradients. The spatial structures and relative magnitudes of the three contributions to Eddy-induced Ekman pumping are investigated by collocating satellite-based measurements of SST, geostrophic velocity, and surface winds to the interiors of eddies identified from their sea surface height signatures. On average, e...
-
randomness symmetry and scaling of Mesoscale Eddy life cycles
Journal of Physical Oceanography, 2014Co-Authors: R M Samelson, Michael G Schlax, Dudley B CheltonAbstract:AbstractIt is shown that the life cycles of nonlinear Mesoscale eddies, a major component of low-frequency ocean physical variability, have a characteristic structure that differs fundamentally from that which would be expected on the basis of classical interpretations of ocean Eddy evolution in terms of mean flow instability and equilibration followed by frictional, radiative, or barotropic decay, or of vortex merger dynamics in quasigeostrophic turbulent cascades. Further, it is found that these life cycles can be accurately modeled in terms of the large-amplitude excursions of a stochastic process. These conclusions, which apply in the corresponding global-mean context, follow from the examination of ensemble-mean and standard deviation time series of normalized Eddy amplitude from an automated Eddy identification and tracking analysis of a nearly two decade–merged satellite altimeter record of global sea surface height (SSH). The resulting series are found to have several striking and unexpected chara...
-
ocean atmosphere coupling Mesoscale Eddy effects
Nature Geoscience, 2013Co-Authors: Dudley B CheltonAbstract:Interactions between the ocean and atmosphere are complex. An analysis of satellite data from the Southern Ocean reveals a tight coupling of ocean and atmosphere on horizontal scales of around 100 km that modifies both near-surface winds and ocean circulation.
Pascal Riviere - One of the best experts on this subject based on the ideXlab platform.
-
propagation of wind energy into the deep ocean through a fully turbulent Mesoscale Eddy field
Journal of Physical Oceanography, 2008Co-Authors: Eric Danioux, Patrice Klein, Pascal RiviereAbstract:Abstract The authors analyze the 3D propagation of wind-forced near-inertial motions in a fully turbulent Mesoscale Eddy field with a primitive equation numerical model. Although the wind stress is uniform, the near-inertial motion field quickly becomes spatially heterogeneous, involving horizontal scales much smaller than the Eddy scales. Analysis confirms that refraction by the Eddy relative vorticity is the main mechanism responsible for the horizontal distortion of the near-inertial motions, which subsequently triggers their vertical propagation. An important result is the appearance of two maxima of near-inertial vertical velocity (both with rms values reaching 40 m day−1): one at a depth of 100 m and another unexpected one much below the main thermocline around 1700 m. The shallow maximum, captured by the highest vertical normal modes, involves near-inertial motions with a spatial heterogeneity close to the Eddy vorticity gradient field. These characteristics match analytical results obtained with Y...
-
Propagation of wind energy into the deep ocean through a fully turbulent Mesoscale Eddy field.
Journal of Physical Oceanography, 2008Co-Authors: Eric Danioux, Patrice Klein, Pascal RiviereAbstract:We analyse the 3-D propagation of wind-forced near-inertial motions in a fully turbulent Mesoscale Eddy field with a primitive-equation numerical model. Although the wind-stress is uniform, the near-inertial motion field quickly becomes spatially heterogeneous, involving horizontal scales much smaller than the Eddy scales. Analysis confirms that refraction by the Eddy relative vorticity is the main mechanism responsible for the horizontal distortion of the near-inertial motions, which subsequently triggers their vertical propagation. An important result is the appearance of two maxima of near-inertial vertical velocity (both with r.m.s. values reaching 40 m/day): one at a depth of 100 m and another unexpected one much below the main thermocline around 1700 m. The shallow maximum, captured by the highest vertical normal modes, involves near-inertial motions with a spatial heterogeneity close to the Eddy vorticity gradient field. These characteristics match analytical results obtained with Young and Ben Jelloul (1997)'s approach. The deep maximum, captured by the lowest vertical normal modes, involves superinertial motions with a frequency of twice the inertial frequency and much smaller horizontal scales. Because of these characteristics, not anticipated by previous analytical studies, these superinertial motions may represent an energy source for small-scale mixing through a mechanism not taken into account in the present study: the parametric subharmonic instability (PSI). This reveals a pathway by which wind energy may have a significant impact on small-scale mixing in the deep interior. Further studies that explicitly take into account PSI are needed to estimate this potential impact.