Near-Inertial Oscillations and the Damping of Midlatitude Gyres: A Modeling Study

Gertz, Aaron B.; Straub, David

doi:10.1175/2009jpo4058.1

Cited by 28 publications

(18 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, several studies have observed NIWs transferring energy to balanced flows. Gertz & Straub (2009), for example, on examining the dynamics of wind forced oceanic gyres, found that in regions of the gyre where the balanced flow was weak, particularly at large scales, the balanced flow extracted energy from waves. In a different configuration, investigating strongly nonlinear interactions between NIWs and fronts, Thomas & Taylor (2014) found that NIWs transferred energy to geostrophic currents, this being catalyzed by parametric subharmonic instability.…”

Section: Discussionmentioning

confidence: 99%

“…However, recent theoretical and numerical investigations are beginning to demand a reconsideration of above pathways. Various energetic interactions between balanced flows and inertia-gravity waves have been uncovered, at O(1) Rossby numbers (Gertz & Straub 2009;Taylor & Straub 2016;Barkan et al 2017;Thomas 2017 and references therein) and asymptotically small Rossby numbers (Wagner & Young 2015;Xie & Vanneste 2015;Rocha et al 2018). Nevertheless, these investigations have focused primarily on high baroclinic mode NIWs.…”

Section: Discussionmentioning

confidence: 99%

“…Both these investigations found NIWs extracting energy from balanced flows. Gertz & Straub (2009) examined the interaction of externally forced NIWs on balanced flows within a set-up motivated by wind-driven ocean gyres. Gertz & Straub found that the balanced flow could gain or lose energy to waves.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Geophysical turbulence dominated by inertia–gravity waves

Thomas

Yamada

2019

J. Fluid Mech.

View full text Add to dashboard Cite

Recent evidence from both oceanic observations and global-scale ocean model simulations indicate the existence of regions where low-mode internal tidal energy dominates over that of the geostrophic balanced flow. Inspired by these findings, we examine the effect of the first vertical mode inertia–gravity waves on the dynamics of balanced flow using an idealized model obtained by truncating the hydrostatic Boussinesq equations on to the barotropic and the first baroclinic mode. On investigating the wave–balance turbulence phenomenology using freely evolving numerical simulations, we find that the waves continuously transfer energy to the balanced flow in regimes where the balanced-to-wave energy ratio is small, thereby generating small-scale features in the balanced fields. We examine the detailed energy transfer pathways in wave-dominated flows and thereby develop a generalized small Rossby number geophysical turbulence phenomenology, with the two-mode (barotropic and one baroclinic mode) quasi-geostrophic turbulence phenomenology being a subset of it. The present work therefore shows that inertia–gravity waves would form an integral part of the geophysical turbulence phenomenology in regions where balanced flow is weaker than gravity waves.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Geophysical turbulence dominated by inertia–gravity waves

Thomas

Yamada

2019

J. Fluid Mech.

View full text Add to dashboard Cite

show abstract

“…Such instabilities are however absent from other high‐resolution simulations of upper ocean geostrophic turbulence [ Klein et al , ], calling for further investigation. Now, while internal waves or inertial oscillations may play a role in the forward energy cascade leading to dissipation, it is those forced by other mechanisms, particularly winds, that are likely involved [ Gertz and Straub , ]. In both cases, the focus has moved away from spontaneously generated gravity waves.…”

Section: Impacts and Parameterizationsmentioning

confidence: 99%

Internal gravity waves from atmospheric jets and fronts

2014

View full text Add to dashboard Cite

For several decades, jets and fronts have been known from observations to be significant sources of internal gravity waves in the atmosphere. Motivations to investigate these waves have included their impact on tropospheric convection, their contribution to local mixing and turbulence in the upper troposphere, their vertical propagation into the middle atmosphere, and the forcing of its global circulation. While many different studies have consistently highlighted jet exit regions as a favored locus for intense gravity waves, the mechanisms responsible for their emission had long remained elusive: one reason is the complexity of the environment in which the waves appear; another reason is that the waves constitute small deviations from the balanced dynamics of the flow generating them; i.e., they arise beyond our fundamental understanding of jets and fronts based on approximations that filter out gravity waves. Over the past two decades, the pressing need for improving parameterizations of nonorographic gravity waves in climate models that include a stratosphere has stimulated renewed investigations. The purpose of this review is to present current knowledge and understanding on gravity waves near jets and fronts from observations, theory, and modeling, and to discuss challenges for progress in coming years.

show abstract

“…Another, more remarkable perhaps, is that they alter the slow, balanced oceanic circulation directly through wave-mean-flow interaction processes. Gertz & Straub (2009) put forward the idea that NIWs provide an energy sink for this circulation. Their numerical simulations suggest that this process may be significant and, along with other mechanisms including bottom and surface friction (e.g.…”

Section: Introductionmentioning

confidence: 99%

A generalised-Lagrangian-mean model of the interactions between near-inertial waves and mean flow

Xie

Vanneste

2015

J. Fluid Mech.

View full text Add to dashboard Cite

Wind forcing of the ocean generates a spectrum of inertia-gravity waves that is sharply peaked near the local inertial (or Coriolis) frequency. The corresponding near-inertial waves (NIWs) are highly energetic and play a significant role in the slow, large-scale dynamics of the ocean. To analyse this role, we develop a new model of the nondissipative interactions between NIWs and balanced motion. The model is derived using the generalised-Lagrangian-mean (GLM) framework (specifically, the glm variant of Soward & Roberts (2010)), taking advantage of the time-scale separation between the two types of motion to average over the short NIW period.We combine Salmon's (2013) variational formulation of GLM with Whitham averaging to obtain a system of equations governing the joint evolution of NIWs and mean flow. Assuming that the mean flow is geostrophically balanced reduces this system to a simple model coupling Young & Ben Jelloul's (1997) equation for NIWs with a modified quasigeostrophic equation. In this coupled model, the mean flow affects the NIWs through advection and refraction; conversely, the NIWs affect the mean flow by modifying the potential-vorticity inversion -the relation between advected potential vorticity and advecting mean velocity -through a quadratic wave term, consistent with the GLM results of Bühler & McIntyre (1998).The coupled model is Hamiltonian and its conservation laws, for wave action and energy in particular, prove illuminating: on their basis, we identify a new interaction mechanism whereby NIWs forced at large scales extract energy from the balanced flow as their horizontal scale is reduced by differential advection and refraction so that their potential energy increases. A rough estimate suggests that this mechanism could provide a significant sink of energy for mesoscale motion and play a part in the global energetics of the ocean.Idealised two-dimensional models are derived and simulated numerically to gain insight into NIW-mean-flow interaction processes. A simulation of a one-dimensional barotropic jet demonstrates how NIWs forced by wind slow down the jet as they propagate into the ocean interior. A simulation assuming plane travelling NIWs in the vertical shows how a vortex dipole is deflected by NIWs, illustrating the irreversible nature of the interactions. In both simulations energy is transferred from the mean flow to the NIWs.

show abstract

Near-Inertial Oscillations and the Damping of Midlatitude Gyres: A Modeling Study

Cited by 28 publications

References 30 publications

Geophysical turbulence dominated by inertia–gravity waves

Geophysical turbulence dominated by inertia–gravity waves

Internal gravity waves from atmospheric jets and fronts

A generalised-Lagrangian-mean model of the interactions between near-inertial waves and mean flow

Contact Info

Product

Resources

About