The Challenger Deep (CD) is the deepest known hadal trench in the world. Due to challenges in data sampling at extreme ocean depths, the Lower Circumpolar Deep Water (LCDW) transport and ocean circulation structure in the CD remain unclear. By analyzing data from an extra-deep current meter mooring array, here we find a three-layer circulation in the CD, transitioning downward from westward LCDW flow (about −1.866 ± 2.953 Sv, 1 Sv = 10⁶ m³/s) to cyclonic circulation, and then to anticyclonic circulation. The westward flow reverses its direction during summer, giving evidence for bidirectional connectivity of deep-sea basins, while the cyclonic-anticyclonic circulation is relatively steady. The LCDW intrusion, local topography and turbulent mixing are crucial for modulating the three-layer circulation. Turbulent mixing plays a key role in driving the anticyclonic circulation. Our findings provide insights for understanding the hydrodynamic environment in the ocean’s deepest areas.

In this study, M₂ tidal energy and tide-induced mixing in the Mariana double ridges are investigated with a high-resolution three-dimensional non-hydrostatic numerical model and baroclinic energy budget analysis. The interference effect of the double ridges on the internal tide in the Mariana is examined by omitting either the eastern or the western ridge. Our results show that the baroclinic velocity on the sides of the interior facing slopes of the double ridges is larger than that on the other sides. In the double ridges, high values of dissipation reaching O (10⁻⁶ W kg⁻¹) are accompanied by diapycnal diffusivity reaching O (10⁻¹ m² s⁻¹), which is several orders of magnitude higher than the mixing of the open ocean. The bottom diapycnal mixing in the inner region between the two ridges is one order of magnitude larger than the mixing outside the ridges, indicating the important role of the interference of the double-ridge topography on the mixing in the Mariana Arc. Omitting either the eastern or the western ridge would have a significant impact on tide current, baroclinic energy flux and dissipation, and diapycnal mixing. The internal tide conversion, dissipation, and flux divergence are amplified by the double ridge topography, especially in the central part of the double ridges. Through energy budgets analysis, we conclude that the eastern ridge is the main source of the baroclinic tide in the Mariana double ridges.

By analyzing dataset derived from four moorings during spring 2022, this study provides direct evidence that near-inertial waves (NIWs) can be largely enhanced by a passing cyclonic eddy (CE) in the northwestern South China Sea. Results show that the enhancement of NIWs mainly occurred at north side of the CE due to asymmetry of eddy structure. In vertical, the enhancement concentrated at above 200 m and reached peaks at around 100 m. Significant energy transfer rates between the CE and NIWs appeared at the same depth of the enhancement that can reach up to 6×10^-10 m²/s³ at the CE’s edge. Under impact of the CE, power of the first five NIWs modes were promoted significantly and dominated by the second and third modes. Overall, the CE transferred energy to NIWs before near-inertial kinetic energy reaching its peaks, while NIWs gave energy back to the CE after the peaks.

By analyzing datasets derived from four moorings during spring 2022, this study provides direct evidence that near-inertial waves (NIWs) can be largely enhanced by a passing cyclonic eddy (CE) in the northwestern South China Sea. Results show that the enhancement of NIWs mainly occurred at north side of the CE due to asymmetry of eddy structure. In vertical, the enhancement concentrated at above 200 m and reached peaks at around 100 m. Significant energy transfer rates between the CE and NIWs appeared at the same depth of the enhancement can reach a magnitude of 10⁻⁸ m² s⁻³ at the CE's edge. Under the impact of the CE, power of the first five NIWs modes was promoted significantly and dominated by the second and third modes. Overall, the CE transferred energy to NIWs before near-inertial kinetic energy reaching its peaks, while NIWs gave energy back to the CE after the peaks.

This datasets was used in the study named 'Ocean circulation in the Challenger Deep derived from super-deep underwater glider observation'. It contains temperature, salinity and zonal velocity data. Please let me know if you need any more information.

By analyzing dataset derived from four moorings during spring 2022, this study provides direct evidence that near-inertial waves (NIWs) can be largely enhanced by a passing cyclonic eddy (CE) in the northwestern South China Sea. Results show that the enhancement of NIWs mainly occurred at north side of the CE due to asymmetry of eddy structure. In vertical, the enhancement concentrated at above 200 m and reached peaks at around 100 m. Significant energy transfer rates between the CE and NIWs appeared at the same depth of the enhancement that can reach up to 6×10^-10 m²/s³ at the CE’s edge. Under impact of the CE, power of the first five NIWs modes were promoted significantly and dominated by the second and third modes. Overall, the CE transferred energy to NIWs before near-inertial kinetic energy reaching its peaks, while NIWs gave energy back to the CE after the peaks.