Internal waves over the shelf in the western Bay of Bengal: a case study

Joshi, Madhu; Rao, A. D.; Mohanty, Sachiko; Pradhan, Himansu Kesari; Murty, V. S. N.; Prasad, K. Venkatesh

doi:10.1007/s10236-016-1006-3

Cited by 13 publications

(4 citation statements)

References 28 publications

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“…Some of these studies reported that internal tides in this region are mainly generated at the shelf breaks and on the continental slopes (Rao et al, ). Surface manifestations of shoreward propagating short period internal waves in the western BoB, particularly in the northern part of the coast (18–19°N), were also reported based on Synthetic Aperture Radar (SAR) imageries (Joshi et al, ; Prasad & Rajasekhar, ). Some previous studies noted strong internal tide generation near the head Bay and temporal variability in internal tide activity due to changes in stratification (Pradhan et al, ; Rao et al, ).…”

Section: Introductionmentioning

confidence: 70%

“…Earlier studies on semidiurnal internal tides in the western BoB were mainly based on short records (a few days) of currents and temperature as well as simulations using numerical models (Joshi et al, ; Mohanty et al, ; Pradhan et al, ; Pradhan et al, ; Rao et al, ; Rao et al, ). Some of these studies reported that internal tides in this region are mainly generated at the shelf breaks and on the continental slopes (Rao et al, ).…”

Section: Introductionmentioning

confidence: 99%

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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: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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

et al. 2019

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“…Pradhan et al 6 adopted the MIT-GCM model for the simulation of IWs in the western BOB and later studied their variability during spring-neap conditions by Pradhan et al 7 and their interseasonal variability 8 . Similar work was carried out by Joshi et al 9 to study the generation and propagation of IWs in the western BOB. Phaniharam et al 10 studied IW characteristics along the northwestern BOB using SAR imagery.…”

Section: Introductionmentioning

confidence: 70%

Study on Internal Waves over the Bay of Bengal Using ALOS PALSAR L band SAR Imageries

Phaniharam,

Vignudelli,

et al. 2024

Preprint

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Using ALOS PALSAR L-band SAR data, internal waves (IWs) with distinct characteristics ranging from weak manifestations to strong signatures are observed throughout the continental shelf edge of the Bay of Bengal and are not confined to a particular region or season. The wavelength, phase speed, and amplitude may vary depending upon the oceanic environmental conditions. The wavelengths computed from the present study vary from 0.17 to 4.8 km, and the phase speed ranges from 0.04 to 0.2 m/s. An attempt was made to study the morphological features of IWs using SAR imagery. IWs with different signatures (elevation and depression) were observed. Interestingly, they coexist simultaneously and crossover in the BOB. This may imply that either the IWs generated from the deep ocean propagating over shelf regions may be reflected or that river discharge may act as a force to disturb stratified layers. In this study, depressed IWs generated off the Kakinada region by the Godavari River plume were observed, and similar IW characteristics were observed in the head BOB. This may imply that many other major and minor rivers may act as another source for the generation of IWs. However, this aspect of the study needs further investigation in the BOB.

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“…In the northern BoB, strong stratification prevails at the end of the SW monsoon and a weaker stratification prior to the SW monsoon (March-May) [8,9]. Madhu et al [10] studied the generation and propagation of IWs in the shelf waters of the western BoB from observations and using the Massachusetts Institute of Technology (MIT) general circulation model (MITgcm) forced with astronomical tides and daily winds for winter 2012 and identified the zones of sources/sinks for the generation of internal tides in the northwestern BoB to lie along the isobaths (500 m and 1500 m). These authors reported the phase speed of internal tides as 0.75 m/s in the open sea waters and 0.45 m/s on the shelf waters from Envisat SAR imagery in February 2012.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal

2023

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Internal waves (IWs) are generated in all the oceans, and their amplitudes are large, especially in regions that receive a large amount of freshwater from nearby rivers, which promote highly stratified waters. When barotropic tides encounter regions of shallow bottom-topography, internal tides (known as IWs of the tidal period) are generated and propagated along the pycnocline due to halocline or thermocline. In the North Indian Ocean, the Bay of Bengal (BoB) and the Andaman Sea receive a large volume of freshwater from major rivers and net precipitation during the summer monsoon. This study addresses the characteristics of internal tides in the BoB and Andaman Sea using NASA’s Estimating the Circulation and Climate of the Ocean (ECCO) project’s high-resolution (1/48° and hourly) salinity estimates at 1 m depth (hereafter written as ECCO salinity) during September 2011–October 2012, time series of temperature, and salinity profiles from moored buoys. A comparison is made between ECCO salinity and NASA’s Soil Moisture Active Passive (SMAP) salinity and Aquarius salinity. The time series of ECCO salinity and observed salinity are subjected to bandpass filtering with an 11–14 h period and 22–26 h period to detect and estimate the characteristics of semi-diurnal and diurnal period internal tides. Our analysis reveals that the ECCO salinity captured well the surface imprints of diurnal period internal tide propagating through shallow pycnocline (~50 m depth) due to halocline, and the latter suppresses the impact of semi-diurnal period internal tide propagating at thermocline (~100 m depth) reaching the sea surface. The semi-diurnal (diurnal) period internal tides have their wavelengths and phase speeds increased (decreased) from the central Andaman Sea to the Sri Lanka coast. Propagation of diurnal period internal tide is dominant in the northern BoB and northern Andaman Sea.

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Internal waves over the shelf in the western Bay of Bengal: a case study

Cited by 13 publications

References 28 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

Study on Internal Waves over the Bay of Bengal Using ALOS PALSAR L band SAR Imageries

Characteristics of Internal Tides from ECCO Salinity Estimates and Observations in the Bay of Bengal

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