Generation of Internal Waves by Eddies Impinging on the Western Boundary of the North Atlantic

Clement, Louis; Frajka‐Williams, Eleanor; Sheen, Katy; Brearley, J. Alexander; Garabato, Alberto C. Naveira

doi:10.1175/jpo-d-14-0241.1

Cited by 43 publications

(54 citation statements)

References 47 publications

(44 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several lines of evidence have suggested the existence of propagating lee waves (e.g., Naveira St. Laurent et al 2012;Waterman et al 2013;Sheen et al 2013Sheen et al , 2014Clement et al 2016; Fig. 5a).…”

Section: Internal Lee Waves Theory and Observationsmentioning

confidence: 87%

Climate Process Team on Internal Wave–Driven Ocean Mixing

MacKinnon

Zhao

Whalen

et al. 2017

Bulletin of the American Meteorological Society

279

207

View full text Add to dashboard Cite

O cean turbulence influences the transport of heat, freshwater, dissolved gases such as CO 2 , pollutants, and other tracers. It is central to understanding ocean energetics and reducing uncertainties in global circulation and simulations from climate models. The dissipation of turbulent energy in stratified water results in irreversible diapycnal (across density surfaces) mixing. Recent work has shown that the spatial and temporal inhomogeneity in diapycnal mixing may play a critical role in a variety of climate phenomena. Hence, a quantitative understanding of the physics that drive the distribution of diapycnal mixing in the ocean interior is fundamental to understanding the ocean's role in climate.Diapycnal mixing is very difficult to accurately parameterize in numerical ocean models for two reasons. The first one is due to the discrete representation of tracer advection in directions that are not perfectly aligned with isopycnals, which can result in numerically induced mixing from truncation errors that is larger than observed diapycnal mixing (Griffies et al. 2000;Ilıcak et al. 2012). The second reason is related to the intermittency of turbulence, which is generated by complex and chaotic motions that span a large space-time range. Furthermore, this mixing is driven by a wide range of processes with distinct governing physics that create a rich global geography [see MacKinnon et al. (2013c) for a review]. The difficulty is also related to the relatively sparse direct sampling of ocean mixing, whereby sophisticated ship-based measurements are generally required to accurately characterize ocean mixing processes. Nonetheless, we have sufficient evidence from theory, process models, laboratory experiments, and field measurements to conclude that away from ocean boundaries (atmosphere, ice, or the solid ocean bottom), diapycnal mixing is largely related to the breaking of internal gravity waves, which have a complex dynamical underpinning and associated geography. The study summarizes recent advances in our understanding of internal wave-driven turbulent mixing in the ocean interior and introduces new parameterizations for global climate ocean models and their climate impacts.

show abstract

Section: Internal Lee Waves Theory and Observationsmentioning

confidence: 87%

Climate Process Team on Internal Wave–Driven Ocean Mixing

MacKinnon

Zhao

Whalen

et al. 2017

Bulletin of the American Meteorological Society

279

207

View full text Add to dashboard Cite

show abstract

“…These regions host intense mesoscale activity and above‐average near‐inertial energy input from atmospheric storms (e.g., Alford, ; Shum et al, ). It is likely that nontidal processes account for the bulk of the inferred internal wave energy dissipation there (Clément et al, ; Nikurashin et al, ; Pollmann et al, ; Waterman et al, ; Whalen et al, ) and therefore for the discrepancy with the present climatology. The dissipation map of Whalen et al () also displays a band of enhanced turbulence along the equator (Figure c) that is absent from the ϵ tid climatology (Figure a).…”

Section: Comparison To Microstructure and Finestructure Observationsmentioning

confidence: 94%

A Parameterization of Local and Remote Tidal Mixing

Lavergne

Vic

Madec

et al. 2020

J Adv Model Earth Syst

View full text Add to dashboard Cite

Vertical mixing is often regarded as the Achilles' heel of ocean models. In particular, few models include a comprehensive and energy-constrained parameterization of mixing by internal ocean tides. Here, we present an energy-conserving mixing scheme which accounts for the local breaking of high-mode internal tides and the distant dissipation of low-mode internal tides. The scheme relies on four static two-dimensional maps of internal tide dissipation, constructed using mode-by-mode Lagrangian tracking of energy beams from sources to sinks. Each map is associated with a distinct dissipative process and a corresponding vertical structure. Applied to an observational climatology of stratification, the scheme produces a global three-dimensional map of dissipation which compares well with available microstructure observations and with upper-ocean finestructure mixing estimates. This relative agreement, both in magnitude and spatial structure across ocean basins, suggests that internal tides underpin most of observed dissipation in the ocean interior at the global scale. The proposed parameterization is therefore expected to improve understanding, mapping, and modeling of ocean mixing.Plain Language Summary When tidal ocean currents flow over bumpy seafloor, they generate internal tidal waves. Internal waves are the subsurface analog of surface waves that break on beaches. Like surface waves, internal tidal waves often become unstable and break into turbulence. This turbulence is a primary cause of mixing between stacked ocean layers-a key process regulating ocean currents and biology and a key ingredient of computer models of the global ocean. In this article, a three-dimensional global map of mixing induced by internal tidal waves is presented. This map incorporates a large variety of energy pathways from the generation of tidal waves to turbulence, accounting for the conservation of energy. The map is compared to available observations of turbulence across the globe and found to reproduce with good fidelity the main patterns identified in observations. This relatively good agreement suggests that internal tidal waves are the main source of turbulence in the subsurface ocean and implies that the map may serve a range of applications. In particular, the three-dimensional map provides an efficient and realistic means to represent mixing by internal tidal waves in global ocean models.

show abstract

“…Internal tides are generated in areas where the barotropic tide interacts with rough or steep topography, and the global pattern of internal tide generation is a product of topographic roughness, tidal strength, and stratification. On the global scale, the low‐mode waves (wavelengths of a few kilometers to about 100 to 200 km, group velocities in the order of 1 m s −1 ) carry a major part of the energy converted from the barotropic tide (e.g., Falahat et al, ), but in regions of rough small‐scale topography such as mid‐ocean ridges (Falahat et al, ; St. Laurent & Garrett, ; Vic et al, , ) or eddy‐slope interaction such as western boundaries (Clément et al, ; Köhler et al, ), more energy can be contained in higher modes. The higher mode waves break near the generation region and dissipate locally (e.g., Klymak et al, ; Vic et al, ), while low‐mode internal tides as well as the wind generated near‐inertial waves can radiate far away from their sources (e.g., Alford, ; Alford & Zhao, ).…”

Section: Introductionmentioning

confidence: 99%

Energy Flux Observations in an Internal Tide Beam in the Eastern North Atlantic

et al. 2019

View full text Add to dashboard Cite

Low‐mode internal waves propagate over large distances and provide energy for turbulent mixing when they break far from their generation sites. A realistic representation of the oceanic energy cycle in ocean and climate models requires a consistent implementation of their generation, propagation, and dissipation. Here we combine the long‐term mean energy flux from satellite altimetry with results from a 1/10° global ocean general circulation model that resolves the low modes of internal waves and in situ observations of stratification and horizontal currents to study energy flux and dissipation along a 1000 km internal tide beam in the eastern North Atlantic. Internal wave fluxes were estimated from twelve 36‐ to 48‐hr stations in along‐ and across‐beam direction to resolve both the inertial period and tidal cycle. The observed internal tide energy fluxes range from 5.9 kW m−1 near the generation sites to 0.5 kW m−1 at distant stations. Estimates of energy dissipation come from both finestructure and upper ocean microstructure profiles and range, vertically integrated, from 0.5 to 3.3 mW m−2 along the beam. Overall, the in situ observations confirm the internal tide pattern derived from satellite altimetry, but the in situ energy fluxes are more variable and decrease less monotonically along the beam. Internal tides in the model propagate over shorter distances compared to results from altimetry and in situ measurements, but more spatial details close the main generation sites are resolved.

show abstract

Generation of Internal Waves by Eddies Impinging on the Western Boundary of the North Atlantic

Cited by 43 publications

References 47 publications

Climate Process Team on Internal Wave–Driven Ocean Mixing

Climate Process Team on Internal Wave–Driven Ocean Mixing

A Parameterization of Local and Remote Tidal Mixing

Energy Flux Observations in an Internal Tide Beam in the Eastern North Atlantic

Contact Info

Product

Resources

About