Observed equatorward propagation and chimney effect of near-inertial waves in the mid-latitude ocean

Yu, Xiaolong; Garabato, Alberto C. Naveira; Vic, Clément; Gula, Jonathan; Savage, Anna C.; Wang, Jinbo; Waterhouse, Amy F.; MacKinnon, Jennifer A.

doi:10.1002/essoar.10510719.1

Cited by 3 publications

(5 citation statements)

References 42 publications

(51 reference statements)

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“…It is clear from Figure 9a that the observed strong turbulence was located below the strongest stratification at depths of 30–40 m. Instead, S 2 peaked right in (instead of below) the strongest stratification layer (∼23 m depth, Figure 9b). Previous studies have also documented that the near‐inertial shear was most likely quickly dissipated at the base of the mixed layer (e.g., Yu et al., 2022). There was a secondary large shear layer lying below the isopycnal of 25 kg m −3 at depth of ∼40 m during the first 8 hr.…”

Section: Discussionmentioning

confidence: 91%

“…H08 was characterized by moderate wind speed (∼8 m s −1 ) during the observation period, the wind generally showed a quite intermittent feature during the 1‐month period since August 13. The wind energy flux into near‐inertial motions can be dominated by such intermittent events with duration of several days (Yu et al., 2022), resulting in prevailing near‐inertial responses in the mixed layer (Figure 7b).…”

Section: Resultsmentioning

confidence: 99%

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Widespread Intensified Pycnocline Turbulence in the Summer Stratified Yellow Sea

et al. 2023

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Pycnocline mixing lies at the heart of seasonally stratified shelf sea systems, regulating vertical exchange of momentum, mass, heat, and biogeochemical constituents. Based on microstructure measurements in the summer of 2013 and 2017, here we report on the widespread occurrence of intensified pycnocline turbulence in the summer stratified Yellow Sea (YS). Large turbulent kinetic energy dissipation rates ε $\varepsilon $ ∼ scriptO $\mathcal{O}$ (10−7 W kg−1) and microscale thermal dissipation rates χ $\chi $ ∼ scriptO $\mathcal{O}$ (10−6 K2 s−1) are found in the pycnocline below the depth of the strongest stratification at many sampling stations. Shipboard velocity measurements suggest that wind‐induced near‐inertial internal waves induced strong velocity shear; however, the calculated velocity shear peaked exactly at (instead of below) the strongest stratification layer and is generally not strong enough to trigger shear instabilities according to the Richardson number criterion. Example results at two repeated sampling stations clearly showed the presence of a low‐salinity water layer (with a thickness of 5–15 m), at the upper boundary of which salt fingering is expected to occur according to the Turner angle. The observed elevated ε $\varepsilon $ and χ $\chi $ tended to occur in the salt‐finger‐favorable layers. Although the distribution of ε $\varepsilon $ and χ $\chi $ reveals the relation with Turner angle, we further note the possible complexity in the driving mechanisms with the thermohaline‐shear instability potentially playing a role. Given the widespread nature of the intensified pycnocline turbulence, it is expected that this turbulence has important implications for nutrients cycling and thus the maintenance of primary productivity in the summer stratified YS.

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Section: Discussionmentioning

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Widespread Intensified Pycnocline Turbulence in the Summer Stratified Yellow Sea

et al. 2023

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“…We wrote the above equation in abstract form since the YBJ equation can be written in different forms in two and three dimensions [121]. Despite being an approximate asymptotic model, the YBJ equation (3.1) is a robust model that can capture the slow advection, refraction, and scattering of NIWs by balanced flows and subsequent reduction in waves' horizontal scales, vertical propagation of NIWs and accumulation of NIWs in anticyclonic vortices [122][123][124][125][126][127][128][129][130][131].…”

Section: (B) Near-inertial Wavesmentioning

confidence: 99%

Turbulent wave-balance exchanges in the ocean

Thomas

2023

Proc. R. Soc. A.

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Oceanic flows are turbulent and multi-scale in nature, and are composed of fast internal waves and slowly evolving balanced eddies. Contrary to conventional wisdom in physical oceanography, the past two decades of in situ , satellite altimeter and realistically forced global scale ocean model outputs have revealed that internal gravity waves can have comparable or higher energy levels than geostrophically balanced flows at 10–100 km scales in different parts of the world’s oceans. These relatively recent findings have fuelled a wide range of research activities aimed at understanding how fast internal gravity waves interact with slowly evolving balanced flows, particularly with the goal of deducing whether internal waves can form an energy sink for oceanic balanced flows. In this paper, we comprehensively review theoretical, numerical and observational investigations undertaken to study internal wave-balance flow exchanges. Theoretical calculations, inspired by different wave-balance regimes seen in observational and global ocean model outputs, are used to point out that internal waves can affect balanced flow dynamics. The theoretical results are followed up by a detailed discussion of numerical results on wave-balance interactions in a broad set of parameter regimes. The numerical results reveal how different kinds of waves exchange energy with balance flow, affect energy flux across scales of balanced flow and facilitate the generation of small-scale dissipative balanced flow structures. The numerical simulation results and global internal wave energy and balanced energy maps are used to conjecture that out of the 0.8 TW of power going to balanced flow kinetic energy in the ocean, at least 0.1 TW could be dissipated by internal gravity waves. We therefore hypothesize that internal waves can form a non-negligible energy sink for balanced flow in the world’s oceans.

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“…To simplify the calculation, the mean value of C gz of moorings C06 and C08 was substituted into Equation (10). C gz can be estimated by identifying the downwards progression of kinetic energy maxima over time (Yu et al, 2022), resulting in 7.53 m/d at C06 and 38.82 m/d at C08. The time-averaged (from 30 September to 24 October) SLA was used to determine the edge of the eddy (Figure 8 black solid line) and then the F E outside and in the eddy was calculated, as shown in Figures 8A, B.…”

Section: Energy Fluxmentioning

confidence: 99%

“…Most of the NIKE is transmitted into the thermocline and deeper layers by NIWs (D'Asaro et al, 1995;Alford, 2001;Jiang et al, 2005), with some of them even reaching layers deeper than 1000 m [30], demonstrating their potential importance in mixing the deep ocean. Previous studies suggest that typhoongenerated NIWs have horizontal wavelengths of hundreds to thousands km in the upper ocean (Hisaki and Naruke, 2003;Johnston et al, 2021) and large vertical group velocities (tens to hundreds m per day) (Sun L. et al, 2011;Yang et al, 2015;Hou et al, 2019;Yu et al, 2022). The frequency of these NIWs experiences a redshift (frequency below the local inertial frequency f) or a blueshift (frequency above f) under different background flows (Sun L. et al, 2011;Chen et al, 2013;Pallas-Sanz et al, 2016;Hou et al, 2019).…”

mentioning

confidence: 98%

Near-inertial waves generated by typhoon MITAG under the influence of anticyclonic eddy east of Taiwan

Zheng

Ren

et al. 2023

Front. Mar. Sci.

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Based on subsurface mooring observations and HYCOM data, a complete investigation was conducted of the near-inertial waves (NIWs) caused by Typhoon MITAG to the east of Taiwan. HYCOM data were mainly used to reveal the role played by anticyclonic eddies in the propagation of NIWs. The results show that most typhoon-generated NIWs propagate towards negative vorticity, and NIWs near the edge gradually accumulated towards the eddy center and down to 800 m. NIWs propagating through the thermocline to the deep ocean were mainly concentrated in the eddy, and the near-inertial energy flux showed a significant enhancement from 400 to 600 m. Moreover, the downwards propagation of NIWs in the eddy enhanced the kinetic energy of background flow. NIWs outside the anticyclonic eddy dissipated quickly, while inside the eddy, there were high value areas of e-folding time. Dynamic mode decomposition illustrates that the anticyclonic eddy mainly captures higher modes of NIWs, and the state of continuous energy growth of higher modes can be maintained for more than a week. In addition, NIWs can also be carried westwards by the advection of the mean background flow at the eddy’s edge.

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Observed equatorward propagation and chimney effect of near-inertial waves in the mid-latitude ocean

Cited by 3 publications

References 42 publications

Widespread Intensified Pycnocline Turbulence in the Summer Stratified Yellow Sea

Widespread Intensified Pycnocline Turbulence in the Summer Stratified Yellow Sea

Turbulent wave-balance exchanges in the ocean

Near-inertial waves generated by typhoon MITAG under the influence of anticyclonic eddy east of Taiwan

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