Formation of a Quasi-Universal Internal Wave Spectrum by Wind Forcing Alone: Idealized Modeling and Mooring Observations.

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Title: Formation of a Quasi-Universal Internal Wave Spectrum by Wind Forcing Alone: Idealized Modeling and Mooring Observations.
Authors: Zhang, Qian1,2 (AUTHOR), Chen, Zhiwu1 (AUTHOR) zhiwuchen@scsio.ac.cn, Liu, Zhiyu3 (AUTHOR), Qu, Lixin4 (AUTHOR), Lu, Huaihao4 (AUTHOR), Sun, Yuhan1,2 (AUTHOR), He, Qingyou1,5 (AUTHOR), Xu, Jiexin1 (AUTHOR), Gong, Yankun1 (AUTHOR), Cai, Shuqun1 (AUTHOR)
Source: Journal of Physical Oceanography. Jun2026, Vol. 56 Issue 6, p1-18. 18p.
Subjects: Internal waves, Mesoscale eddies, Computer simulation, Wind pressure, Oceanic mixing
Abstract: Oceanic internal waves (IWs) play a key role in diapycnal mixing that sustains the global overturning circulation. Their energy follows a quasi-universal Garrett-Munk (GM) spectrum, traditionally attributed to nonlinear wave-wave interactions under combined wind and tidal forcing. However, growing evidence points to the importance of eddy-wave interactions, but the specific energy contributions from mesoscale and submesoscale motions to this GM spectrum remain unclear. More importantly, the generation of this GM spectrum by eddy-wave interactions has not been observed in the real ocean. In the present work, an idealized numerical model is used to simulate the formation of a GM-like spectrum by eddy-wave interaction under wind forcing alone. Energy transfers are diagnosed in both Eulerian and Lagrangian coordinates using a multi-scale energy and vorticity analysis. It is found that IW energy supplied by mesoscale eddies is comparable to that from submesoscale motions in Lagrangian coordinate, whereas this mesoscale contribution appears much weaker in Eulerian coordinate. Vertically, mesoscale eddies transfer energy to IWs in the upper ocean, while this energy transfer is reversed in the pycnocline. In-situ mooring observations from the Southern Ocean further support the role of eddies in facilitating the generation of a GM-like spectrum under wind forcing alone. Together, these findings clarify the energy pathways through which mesoscale and submesoscale dynamics energize IWs and offer new insight into the dynamical processes that help maintain the GM spectrum. [ABSTRACT FROM AUTHOR]
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Abstract:Oceanic internal waves (IWs) play a key role in diapycnal mixing that sustains the global overturning circulation. Their energy follows a quasi-universal Garrett-Munk (GM) spectrum, traditionally attributed to nonlinear wave-wave interactions under combined wind and tidal forcing. However, growing evidence points to the importance of eddy-wave interactions, but the specific energy contributions from mesoscale and submesoscale motions to this GM spectrum remain unclear. More importantly, the generation of this GM spectrum by eddy-wave interactions has not been observed in the real ocean. In the present work, an idealized numerical model is used to simulate the formation of a GM-like spectrum by eddy-wave interaction under wind forcing alone. Energy transfers are diagnosed in both Eulerian and Lagrangian coordinates using a multi-scale energy and vorticity analysis. It is found that IW energy supplied by mesoscale eddies is comparable to that from submesoscale motions in Lagrangian coordinate, whereas this mesoscale contribution appears much weaker in Eulerian coordinate. Vertically, mesoscale eddies transfer energy to IWs in the upper ocean, while this energy transfer is reversed in the pycnocline. In-situ mooring observations from the Southern Ocean further support the role of eddies in facilitating the generation of a GM-like spectrum under wind forcing alone. Together, these findings clarify the energy pathways through which mesoscale and submesoscale dynamics energize IWs and offer new insight into the dynamical processes that help maintain the GM spectrum. [ABSTRACT FROM AUTHOR]
ISSN:00223670
DOI:10.1175/JPO-D-25-0199.1