Long-Range Internal Tidal Radiation and Remote Dissipation in the South Equatorial Current.
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| Title: | Long-Range Internal Tidal Radiation and Remote Dissipation in the South Equatorial Current. |
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| Authors: | Zhao, Chen1,2 (AUTHOR), Xu, Zhenhua1,3,4 (AUTHOR) xuzhenhua@qdio.ac.cn, You, Jia1 (AUTHOR) youjia@qdio.ac.cn, Zhang, Peiwen1 (AUTHOR) |
| Source: | Journal of Physical Oceanography. Jan2026, Vol. 56 Issue 1, p191-212. 22p. |
| Subjects: | Energy dissipation, Ocean dynamics, Oceanography, Ocean currents, Internal waves, Tidal power |
| Abstract: | Despite that internal tides are well known at midlatitudes due to their strong energy and long-range propagation, near the equator, internal tides are generally too weak to receive sufficient research interest. Utilizing combined numerical simulations and altimeter data, we reveal an M2 internal tidal beam, originating from the Mussau Ridge (MR) with a weak generation of 0.51 GW, radiating much further than expected across the Caroline Basin. The joint effects of the ridge–trench–rise topography, negligible equatorial Earth rotational force, South Equatorial Current refraction, and a shallow and thin thermocline combined to induce this long-range propagation. Dissipation occurs locally near the source, but also remotely within the Caroline Basin due to the long-range propagation. Upper-layer dissipation reaches 10−9 W kg−1, one to two orders of magnitude higher than near the seafloor, and only 21.5% of the total dissipation occurs below 1000 m. The remote dissipation presents the multilayer distribution, first decreasing downward and then increasing near the seafloor. The calculated internal tidal dissipation rates were generally consistent with fine-scale parameterizations, except where f approaches zero, where fine-scale parameterization becomes completely inapplicable. Our study highlights the importance of equatorial internal tide dissipation especially below the thermocline, which should be understood reliably and parameterized differently in ocean and climate models. Significance Statement: Most energetic internal tidal hotspots are distributed in the midlatitude oceans and have been well researched. In contrast, equatorial internal tides are much weaker; therefore, their physics and energetics remain more unknown. In the present study, we reveal a globally unique internal tidal beam [termed South Equatorial Current–tidal beam (SEC-TB)]. The SEC system refracts the tidal beam path mainly via the effect of the subtidal current field and facilitates its long-range westward radiation. Our results show that the remote dissipation in the upper layer reaches 10−9 W kg−1, which is significantly higher than near the seafloor. Our study highlights the significant internal tidal dissipation in the deep equatorial ocean, which supports the deep-sea mixing and has significant implications for realistic mixing parameterization in ocean circulation models. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Despite that internal tides are well known at midlatitudes due to their strong energy and long-range propagation, near the equator, internal tides are generally too weak to receive sufficient research interest. Utilizing combined numerical simulations and altimeter data, we reveal an M2 internal tidal beam, originating from the Mussau Ridge (MR) with a weak generation of 0.51 GW, radiating much further than expected across the Caroline Basin. The joint effects of the ridge–trench–rise topography, negligible equatorial Earth rotational force, South Equatorial Current refraction, and a shallow and thin thermocline combined to induce this long-range propagation. Dissipation occurs locally near the source, but also remotely within the Caroline Basin due to the long-range propagation. Upper-layer dissipation reaches 10−9 W kg−1, one to two orders of magnitude higher than near the seafloor, and only 21.5% of the total dissipation occurs below 1000 m. The remote dissipation presents the multilayer distribution, first decreasing downward and then increasing near the seafloor. The calculated internal tidal dissipation rates were generally consistent with fine-scale parameterizations, except where f approaches zero, where fine-scale parameterization becomes completely inapplicable. Our study highlights the importance of equatorial internal tide dissipation especially below the thermocline, which should be understood reliably and parameterized differently in ocean and climate models. Significance Statement: Most energetic internal tidal hotspots are distributed in the midlatitude oceans and have been well researched. In contrast, equatorial internal tides are much weaker; therefore, their physics and energetics remain more unknown. In the present study, we reveal a globally unique internal tidal beam [termed South Equatorial Current–tidal beam (SEC-TB)]. The SEC system refracts the tidal beam path mainly via the effect of the subtidal current field and facilitates its long-range westward radiation. Our results show that the remote dissipation in the upper layer reaches 10−9 W kg−1, which is significantly higher than near the seafloor. Our study highlights the significant internal tidal dissipation in the deep equatorial ocean, which supports the deep-sea mixing and has significant implications for realistic mixing parameterization in ocean circulation models. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 00223670 |
| DOI: | 10.1175/JPO-D-24-0215.1 |
