Turbulent dissipation along contrasting internal tide paths off the Amazon shelf from AMAZOMIX
<p>The Amazon shelf break is a key oceanic region where strong internal tides (ITs) are generated, playing a substantial role in climate processes and ecosystems through vertical dissipation and mixing. During the AMAZOMIX survey (2021), currents, hydrography, and turbulence were measured over...
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| Main Authors: | , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2025-07-01
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| Series: | Ocean Science |
| Online Access: | https://os.copernicus.org/articles/21/1589/2025/os-21-1589-2025.pdf |
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| Summary: | <p>The Amazon shelf break is a key oceanic region where strong internal tides (ITs) are generated, playing a substantial role in climate processes and ecosystems through vertical dissipation and mixing. During the AMAZOMIX survey (2021), currents, hydrography, and turbulence were measured over the M<span class="inline-formula"><sub>2</sub></span> tidal period (12.42 h) at multiple stations along both high (HTE) and low (LTE) tidal energy paths, covering IT generation and propagation regions off the Amazon shelf. This dataset provides a unique opportunity to assess IT-driven vertical dissipation and quantify its spatial extent and influence in the region.</p>
<p>Microstructure analyses, integrated with hydrographic data, highlighted contrasting dissipation rates. The highest rates occurred at IT generation sites along the HTE paths, while the lowest rates were observed on the slope along the LTE path. Near generation sites, the dissipation rates were elevated, [<span class="inline-formula">10<sup>−6</sup></span>] <span class="inline-formula">W kg<sup>−1</sup></span>, with IT shear contributing <span class="inline-formula">∼60</span> % compared to the mean baroclinic current (MBC) shear. Along IT paths, rates decreased to [<span class="inline-formula">10<sup>−8</sup></span>] <span class="inline-formula">W kg<sup>−1</sup></span> but remained substantial, driven by nearly equal contributions from IT and MBC shear.</p>
<p>A key finding was the relative increase in turbulent dissipation ([<span class="inline-formula">10<sup>−7</sup></span>] <span class="inline-formula">W kg<sup>−1</sup></span>) <span class="inline-formula">∼230</span> km from two distinct IT generation sites at the shelf break. This zone of high mixing was located in an area where the general circulation vanished, coinciding with a region of potential constructive interference of IT rays originating from different generation sites. It also aligned with the occurrence of large-amplitude internal solitary waves (ISWs), suggesting that constructive IT ray interference may generate nonlinear ISWs that lead to enhanced dissipation.</p> |
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| ISSN: | 1812-0784 1812-0792 |