Energetics of Semidiurnal Internal Tides in the Andaman Sea

Mohanty, Sachiko; Rao, A. D.; Latha, G.

doi:10.1029/2018jc013852

Cited by 31 publications

(24 citation statements)

References 42 publications

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“…Along the AN Ridge, large M 2 energy conversion occurs in the southern (1–4 W/m 2 in Box IV) and northern parts (0.1–1.4 W/m 2 in Box III). Strong internal tide generation along the AN Ridge was reported by Mohanty et al () also.…”

Section: Resultssupporting

confidence: 52%

Modeling of Internal Tides in the Western Bay of Bengal: Characteristics and Energetics

et al. 2019

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Generation and propagation of internal tides in the western Bay of Bengal (BoB) are investigated using observations from Acoustic Doppler Current Profilers and simulations from a very high resolution numerical ocean model. Observations show that semidiurnal internal tides in the southern and northern parts of the western BoB are more energetic during neap phase of the local barotropic tide than those during spring phase. Numerical simulations indicate that internal tides generated over the Andaman-Nicobar Ridge propagate westward for about 1,000-1,450 km across the BoB and finally impinge on the continental slopes off the east coast of India after 5-7 days. Energetic internal tides observed during the neap phase of the barotropic tides in the western BoB are mainly due to the arrival of remotely generated internal tides. We show that the variation in the onshore transmission of these remotely generated internal tides due to the topographic slope in the western BoB controls the strength of internal tide activity along the shelf. Superposition of reflected internal tides from continental slope, which are very steep in some regions and onshore propagating-waves generate partly standing waves. Numerical experiments suggest that internal tides coming from remote sources account for more than 80% of the total internal tide energy observed in the western BoB. Internal tide energy dissipation on the continental margins of the western BoB is about 3 to 4 times larger than the local generation, indicating that this region is a sink for remotely generated internal tide energy.

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Section: Resultssupporting

confidence: 52%

Modeling of Internal Tides in the Western Bay of Bengal: Characteristics and Energetics

et al. 2019

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“…The value of the bottom drag coefficient is kept constant at 0.0025 in this configuration. The 3D model set-up is similar to Mohanty et al 13 , which is used to study the energetics of internal tides in the Andaman Sea, except that the western boundary is extended to include RAMA buoy location. The same model is also used in several studies 14 – 16 for understanding the IWs in the western Bay of Bengal.…”

Section: Methodsmentioning

confidence: 99%

Simulation of diurnal variability in vertical density structure using a coupled model

Yadidya

Rao

Mohanty

2021

Sci Rep

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The changes in the physical properties of the ocean on a diurnal scale primarily occur in the surface mixed layer and the pycnocline. Price–Weller–Pinkel model, which modifies the surface mixed layer, and the internal wave model based on Garrett–Munk spectra that calculates the vertical displacements due to internal waves are coupled to simulate the diurnal variability in temperature and salinity, and thereby density profiles. The coupled model is used to simulate the hourly variations in density at RAMA buoy (15° N, 90° E), in the central Bay of Bengal, and at BD12 (10.5° N, 94° E), in the Andaman Sea. The simulations are validated with the in-situ observations from December 2013 to November 2014. The primary advantage of this model is that it could simulate spatial variability as well. An integrated model is also tested and validated by using the output of the 3D model to initialize the coupled model during January, April, July, and October. The 3D model can be used to initialize the coupled model at any given location within the model domain to simulate the diurnal variability of density. The simulations showed promising results which could be further used in simulating the acoustic fields and propagation losses which are crucial for Navy operations.

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“…(7). In addition, Mohanty et al 13 reported that tendency and advection terms are small compared to other terms along the AN Islands and Andaman Sea. Barotropic M 2 tide loses about 65 GW of tidal energy in the entire model domain, in which about 28.5% (19 GW) of this energy is lost by internal tide dissipation and rest of the energy is dissipated by means of bottom friction.…”

Section: Model Simulationsmentioning

confidence: 99%

Intensification of tidally generated internal waves in the north-central Bay of Bengal

Jithin

Subeesh

Francis

et al. 2020

Sci Rep

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Flow of barotropic tidal currents over topographic features, such as continental slopes and submarine ridges, generates internal gravity waves at tidal periods known as internal tides. Amplitude of these waves are generally large near the generation regions. Analysis of Sea Surface Height (SSH) data, derived from satellite altimeter revealed the amplification of internal tides in the semidiurnal period in the north-central Bay of Bengal (BoB) (around 89  E, 16  N), which is about 450 km away from their generation sites. SSH signals found in the north-central BoB (~3 cm) were comparable to the maximum amplitudes (2.5 to 3.5 cm) observed near their potential generation sites in the BoB such as continental slopes in the head of the bay and Andaman-Nicobar (AN) Ridge. Simulations from a high-resolution regional ocean model also confirmed the presence of large internal tide amplitude in the north-central BoB. Our study revealed that convergence of internal tides, which were generated along the concaveshaped source (continental slopes in the head of the bay and the northern parts of AN Ridge), into its focal region caused their amplification in the north-central BoB. It was also found that internal tide energy dissipation rates in this focal region were about 10 times larger than those in other open ocean regions.Periodic flow of tidal currents over steep topography generates vertical oscillations of isopycnal surfaces in the stratified ocean. These internal oscillations propagate away as gravity waves, known as internal tides. Continental margins and submarine ridges are the main sources of this tidally-generated internal gravity waves in the ocean. Previous studies suggest that about 30% of the energy associated with internal tides, especially with high vertical modes, dissipates locally near the generation sites themselves and the remaining 70% of the energy radiates from the source, propagates long distances (O (1000 km)) and ultimately dissipates in deep ocean or in remote continental margins 1-3 . Dissipation of internal tides is one of the important sources of mechanical energy for the vertical mixing in the interior ocean 4 . Several mechanisms have been suggested for the dissipation of long-range propagating internal tides such as interactions with rough topography 5 , interactions with mean flows and eddies 6 , cascade to smaller scales via wave-wave interactions 7 etc. However, the pathways of internal tide energy in the ocean and regions of their energy dissipation are not completely understood.Generally, strong baroclinic currents and large isopycnal displacements at tidal frequencies are observed near their generation sites and their amplitude decreases away from the sources 8,9 . However, spatial variation of internal tides and associated energy dissipation in the ocean can be more complicated due to the interaction of waves from multiple sources 10 . For example, Wang et al. 11 reported that interference of internal tides from different sources results in large spatial inhomogeneity in the energy flu...

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Energetics of Semidiurnal Internal Tides in the Andaman Sea

Cited by 31 publications

References 42 publications

Modeling of Internal Tides in the Western Bay of Bengal: Characteristics and Energetics

Modeling of Internal Tides in the Western Bay of Bengal: Characteristics and Energetics

Simulation of diurnal variability in vertical density structure using a coupled model

Intensification of tidally generated internal waves in the north-central Bay of Bengal

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