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Abstract The Indonesian seas, with their complex passages and vigorous mixing, constitute the only route and are critical in regulating Pacific–Indian Ocean interchange, air–sea interaction, and global climate events. Previous research employing remote sensing and numerical simulations strongly suggested that this mixing is tidally driven and localized in narrow channels and straits, with only a few direct observations to validate it. The current study offers the first comprehensive temporal microstructure observations in the south of Lombok Strait with a radius of 0.05° and centered on 115.54oE and 9.02oS. Fifteen days of tidal mixing observations measured potential temperature and density, salinity, and turbulent energy dissipation rate. The results revealed significant mixing and verified the remotely sensed technique. The south Lombok temporal and depth averaged of the turbulent kinetic energy dissipation rate, and the diapycnal diffusivity from 20 to 250 m are $$\varepsilon$$ ε = 4.15 ± 15.9) × 10–6 W kg–1 and $$K\rho$$ K ρ = (1.44 ± 10.7) × 10–2 m2s–1, respectively. This $$K\rho$$ K ρ is up to 104 times larger than the Banda Sea [ $$K\rho$$ K ρ = (9.2 ± 0.55) × 10–6 m2s–1] (Alford et al. Geophys Res Lett 26:2741–2744, 1999) or the “open ocean” $$K\rho$$ K ρ = 0.03 × 10–4 m2s−1 within 2° of the equator to (0.4–0.5) × 10–4 m2s−1 at 50°–70° (Kunze et al. J Phys Oceanogr 36:1553–1576, 2006). Therefore, nonlinear interactions between internal tides, tidally induced mixing, and ITF plays a critical role regulating water mass transformation and have strong implications to longer-term variations and change of Pacific–Indian Ocean water circulation and climate.

The Indonesian seas, with their complex passages and vigorous mixing, constitute the only route and are critical in regulating Pacific–Indian Ocean interchange, air–sea interaction, and global climate events. Previous research employing remote sensing and numerical simulations strongly suggested that this mixing is tidally driven and localized in narrow channels and straits, with only a few direct observations to validate it. The current study offers the first comprehensive temporal microstructure observations in the south of Lombok Strait with a radius of 0.05° and centered on 115.54oE and 9.02oS. Fifteen days of tidal mixing observations measured potential temperature and density, salinity, and turbulent energy dissipation rate. The results revealed significant mixing and verified the remotely sensed technique. The south Lombok temporal and depth averaged of the turbulent kinetic energy dissipation rate, and the diapycnal diffusivity from 20 to 250 m are ε = 4.15 ± 15.9) × 10–6 W kg–1 and K ρ = (1.44 ± 10.7) × 10–2 m2s–1, respectively. This K ρ is up to 104 times larger than the Banda Sea [ K ρ = (9.2 ± 0.55) × 10–6 m2s–1] (Alford et al. Geophys Res Lett 26:2741–2744, 1999) or the "open ocean" K ρ = 0.03 × 10–4 m2s−1 within 2° of the equator to (0.4–0.5) × 10–4 m2s−1 at 50°–70° (Kunze et al. J Phys Oceanogr 36:1553–1576, 2006). Therefore, nonlinear interactions between internal tides, tidally induced mixing, and ITF plays a critical role regulating water mass transformation and have strong implications to longer-term variations and change of Pacific–Indian Ocean water circulation and climate. [ABSTRACT FROM AUTHOR]

Abstract Barotropic and baroclinic tides were simulated for the Coral and Tasman Seas off eastern Australia and compared to a simulation without tides. Both simulations included geostrophic currents and replicated a current analogous to the East Australian Current (EAC). Tides and tidal currents in most of this region are weak, generally 1–2 cm s−1, with the exception of the far northwest portion of the Coral Sea. Even these weak tides were found to impact the mean EAC-like current transport, enhancing it by 1–4 Sv in some areas. Southward flow increased over the continental shelf. Tides did not appear to impact eddy formation, size, or rotational speed; however, they affected eddy propagation. Cyclonic eddies propagated northward faster with tides than without tides. Tides impacted cross-shelf transport of colder water, with significantly more on-shore transport occurring with tides, particularly equatorward of the diurnal critical latitudes. Cross-shelf transport of nutrient rich water onto the shelf is important in this oligotrophic region. Although the prime source of vertical shear and mixing were mean currents and eddies, tides played a secondary role. Tides influenced mixing by increasing vertical temperature diffusivities to 10−4 to 10−3 m2 s−1 over portions of the continental slope and over rough topography, particularly in regions near the diurnal critical latitudes (27°–30°). In conclusion, even small tides can significantly impact the circulation through their effects on the mean currents, eddy rotation velocities, eddy propagation, and mixing.

Barotropic and baroclinic tides were simulated for the Coral and Tasman Seas off eastern Australia and compared to a simulation without tides. Both simulations included geostrophic currents and replicated a current analogous to the East Australian Current (EAC). Tides and tidal currents in most of this region are weak, generally 1–2 cm s−1, with the exception of the far northwest portion of the Coral Sea. Even these weak tides were found to impact the mean EAC-like current transport, enhancing it by 1–4 Sv in some areas. Southward flow increased over the continental shelf. Tides did not appear to impact eddy formation, size, or rotational speed; however, they affected eddy propagation. Cyclonic eddies propagated northward faster with tides than without tides. Tides impacted cross-shelf transport of colder water, with significantly more on-shore transport occurring with tides, particularly equatorward of the diurnal critical latitudes. Cross-shelf transport of nutrient rich water onto the shelf is important in this oligotrophic region. Although the prime source of vertical shear and mixing were mean currents and eddies, tides played a secondary role. Tides influenced mixing by increasing vertical temperature diffusivities to 10−4 to 10−3 m2 s−1 over portions of the continental slope and over rough topography, particularly in regions near the diurnal critical latitudes (27°–30°). In conclusion, even small tides can significantly impact the circulation through their effects on the mean currents, eddy rotation velocities, eddy propagation, and mixing. [ABSTRACT FROM AUTHOR]

Abstract Strong tidal currents in and around the narrow straits of the Lesser Sunda Islands, Indonesia, affect ocean sea surface temperatures (SST) via non-linear tide-induced mixing. A fortnightly spring–neap cycle in tidal currents can induce a similar cycle in SST, which has been observed to occur in and south of Lombok Strait. Here we report on an atmospheric response to the fortnightly SST cycle which is detected in relative humidity and air temperature measurements at Bali. The fortnightly cycles in both the ocean SST and the Bali atmospheric data have a strong seasonal cycle, with peak signals occurring during boreal summer.

Strong tidal currents in and around the narrow straits of the Lesser Sunda Islands, Indonesia, affect ocean sea surface temperatures (SST) via non-linear tide-induced mixing. A fortnightly spring–neap cycle in tidal currents can induce a similar cycle in SST, which has been observed to occur in and south of Lombok Strait. Here we report on an atmospheric response to the fortnightly SST cycle which is detected in relative humidity and air temperature measurements at Bali. The fortnightly cycles in both the ocean SST and the Bali atmospheric data have a strong seasonal cycle, with peak signals occurring during boreal summer. [ABSTRACT FROM AUTHOR]