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- Title
A Directional Decomposition Method to Estimate the Reflection and Transmission of Nonlinear Internal Waves Over a Slope.
- Authors
Gong, Yankun; Xie, Jieshuo; Xu, Jiexin; Chen, Zhiwu; He, Yinghui; Cai, Shuqun
- Abstract
Multi‐directional propagating nonlinear internal waves (NLIWs) create complex spatial patterns, often making it difficult to quantitatively estimate the reflection and dissipation processes of NLIW energy over a slope. To identify the onshore‐ and offshore‐going wave signals in a regional model, we apply a directional Fourier filter (DFF) method to clarify wave dynamics over varying slopes. First, a series of two‐dimensional analytical solutions of either solitons or NLIW packets are utilized. Next, two‐dimensional numerical experiments indicate that the rate of reflection (dissipation) of energy for the shoaling NLIWs is much lower (higher) than that for the shoaling internal tides over a slope, regardless of varying slope criticality and height. Finally, we apply the DFF method in a three‐dimensional non‐hydrostatic regional model (MITgcm) to directionally decompose the onshore‐ and offshore‐going internal waves (IWs) on the Australian North West Shelf. The model results show that mode‐1 incoming internal tides gradually steepen into NLIWs during the shoaling processes over the slope, and then the reflecting IWs are propagate offshore in the main form of linear IW beams. In addition, the reflectivity of IWs around the Imperieuse Reef is 60% and the offshore‐reflecting IWs quickly dissipate accompanied by an e‐folding length scale of ∼22 km. Plain Language Summary: Nonlinear internal waves (NLIWs) play a crucial role in mass transport and ocean mixing on continental slopes. Therefore, various physical processes, for example, reflection and dissipation, of NLIWs over a slope are of interest to understanding spatial features of wave energy along the sloping boundaries of the world's oceans. Numerical modeling is one of the most important investigation approaches to give a full‐scale picture of NLIW dynamics in a slope region. The Australian North West Shelf (NWS) is well known to be a physiographic hotspot of NLIWs in numerous studies since the last century. Here, we first propose a directional decomposition method (DFF) to separate onshore‐ and offshore‐going internal waves over a continental slope, then apply it to quantitatively identify the reflection, transmission and dissipation processes of NLIWs on the Australian NWS. It is found that the DFF method is capable of simplifying the complicated wave fields by decomposing NLIWs propagating in multiple directions in a regional model with specific spatial and temporal sampling rates. Moreover, the wave energies during the reflection and diffraction processes, due to the blocking effects of the Imperieuse Reef, are quantified. Key Points: A directional decomposition method is proposed to estimate the reflection, transmission, and dissipation of nonlinear internal waves (NLIWs) over a slope in numerical simulationsThe rate of reflection (dissipation) of energy for the shoaling NLIWs is much lower (higher) than that for the shoaling internal tides over the same slopeAbout 60% of shoaling IW energy is reflected due to the blocking effect of the Imperieuse Reef around the Rowley Shoals
- Subjects
INTERNAL waves; NONLINEAR waves; DECOMPOSITION method; OCEANIC mixing; CONTINENTAL slopes; DEEP-sea moorings
- Publication
Journal of Geophysical Research. Oceans, 2022, Vol 127, Issue 10, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2022JC018598