Collaborative Observations of Boundary Currents, Water Mass Variability, and Monsoon Response in the Southern Bay of Bengal

Lee, Craig; Jinadasa, S.U.P.; Anutaliya, Arachaporn; Centurioni, Luca; Fernando, H. J. S.; Hormann, Verena; Lankhorst, Matthias; Rainville, Luc; Send, Uwe; Wijesekera, H. W.

doi:10.5670/oceanog.2016.43

Cited by 27 publications

(25 citation statements)

References 31 publications

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“…• Gliders in the Bay of Bengal off the east and south coasts of Sri Lanka (Figures 5K,L; Lee et al, 2016). • Repeated sections in the Agulhas Current since 2017 as part of Gliders IN the Agulahas (GINA, Krug et al, 2018) following the Shelf Agulhas Glider Experiment (SAGE) in 2015.…”

Section: Boundary Currentsmentioning

confidence: 99%

OceanGliders: A Component of the Integrated GOOS

et al. 2019

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The OceanGliders program started in 2016 to support active coordination and enhancement of global glider activity. OceanGliders contributes to the international efforts of the Global Ocean Observation System (GOOS) for Climate, Ocean Health, and Operational Services. It brings together marine scientists and engineers operating gliders around the world: (1) to observe the long-term physical, biogeochemical, and biological ocean processes and phenomena that are relevant for societal applications; and, (2) to contribute to the GOOS through real-time and delayed mode data dissemination. The OceanGliders program is distributed across national and regional observing systems and significantly contributes to integrated, multi-scale and multi-platform sampling strategies. OceanGliders shares best practices, requirements, and scientific knowledge needed for glider operations, data collection and analysis. It also monitors global glider activity and supports the dissemination of glider data through regional and global databases, in realtime and delayed modes, facilitating data access to the wider community. OceanGliders currently supports national, regional and global initiatives to maintain and expand the capabilities and application of gliders to meet key global challenges such as improved measurement of ocean boundary currents, water transformation and storm forecast.

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Section: Boundary Currentsmentioning

confidence: 99%

OceanGliders: A Component of the Integrated GOOS

et al. 2019

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“…We note that the magnitude of this salinity change at 1°N is much larger than O(0.01) g kg

^{- 1}

difference between deep salinities measured by the glider and by the ship (Figure c) and so does not result from calibration differences between instruments. It is plausible that these eastward flowing (Figure i), relatively fresh waters (salinity less than 35.4 g kg

^{- 1}

) originated in the Bay of Bengal, were advected into the central Arabian Sea by the Northeast Monsoon Current (Lee et al, ; Schott & McCreary, ), and subsequently entrained into the equatorial circulation.…”

Section: Resultsmentioning

confidence: 99%

Equatorial Circulation in the Western Indian Ocean During Onset of the 2018 Summer Monsoon and Links to the Bay of Bengal

Todd

2020

Geophysical Research Letters

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Cross-equator transects occupied by an underwater glider and a research vessel in the western Indian Ocean captured the evolution of equatorial circulation during onset of the boreal summer monsoon in 2018. At the end of the winter monsoon in March, surface currents were westward, while the equatorial undercurrent carried salty Arabian Sea High-Salinity Water eastward. As winds transitioned from westward to eastward during April, an eastward near-surface Wyrtki Jet developed, while the equatorial undercurrent weakened, vanishing by May. A first-mode baroclinic Kelvin wave propagated through the survey region after westward winds relaxed. However, the vertical structure of the evolving circulation was inconsistent with the first baroclinic mode, suggesting the influence of higher modes in setting observed vertical structure. The strong equatorial undercurrent at the end of the winter monsoon allowed high-salinity waters from the western equatorial Indian Ocean to reach the southern Bay of Bengal in summer 2018.Plain Language Summary Circulation throughout the Indian Ocean is strongly influenced by the twice-per-year reversal of the monsoon winds over the basin. New observations collected using both an autonomous underwater glider and a research vessel in 2018 captured the reversal of layered currents in the upper ocean as the northeast (winter) monsoon gave way to the southwest (summer) monsoon. From March to May, near-surface currents switched form westward to eastward, while the eastward equatorial undercurrent weakened and vanished. Equatorial planetary waves play a key role in propagating signals, such as those associated with changing monsoon winds, through the equatorial oceans. An eastward propagating Kelvin wave moving at a speed consistent with the first baroclinic mode was detected by satellite, but the observed vertical structure of the changing currents during the monsoon transition was inconsistent with the first baroclinic mode. Higher-mode waves are suspected to play a role in the evolution of equatorial currents during the monsoon transition. Relatively strong subsurface flow at the end of the winter monsoon carried salty waters originating in the Arabian Sea eastward, leading to a salty subsurface feature in the Bay of Bengal in summer 2018.

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“…Recently, an international team carried out extensive measurements to investigate monsooncurrent dynamics south of Sri Lanka (Lee et al, 2016). Observations from satellite remote sensing, gliders, moorings, drifters, and echo sounders were combined to present a more comprehensive view of the circulation.…”

Section: Introductionmentioning

confidence: 99%

“…After crossing the southern tip of Sri Lanka, the SMC flows around the perimeter of a distinct region of shallow thermocline, the Sri Lanka dome (SLD; Vinayachandran and Yamagata, 1998). Lee et al (2016) also noted strong northward surface geostrophic flow along 8 • N between 83 • E and 84 • E.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of summer monsoon current around Sri Lanka

et al. 2019

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From June-September, the summer monsoon current (SMC) flows eastward south of Sri Lanka and bends northeastward to form a swift jet that enters the Bay of Bengal (BoB). As such, it is a crucial part of the water exchange between the Arabian Sea (AS) and BoB. The processes that determine the evolution, intensification and meandering of the SMC are only partly understood. They involve both local and remote forcing by the wind, as well as interactions with westward-propagating Rossby waves and eddies. In this study, we investigate these processes using an Indian-Ocean general circulation model (MOM4p1) that is capable of simulating the SMC realistcally. Because eddies and meanders are smoothed out in the climatology, our analyses focus on a single year of 2009, a period when a strong anticyclonic bend in the SMC was observed.An eddy-kinetic-energy budget analysis shows the region to be a zone of significant eddy activity, where both barotropic and baroclinic instabilities are active. Based on the analysis, we classify the evolution of SMC into stages of onset, intensification, anticyclonic bend, anticyclonic vortex formation, meandering and termination. In addition, analysis of eddypotential-vorticity flux and eddy-enstrophy decay reveal when, where, and how the eddies tend to drive the mean flow. Rossby waves and westward-propagating eddies arriving from the east energize the SMC in June and accelerate the mean flow through an up-gradient eddy-potential-vorticity flux. At the same time, local winds also strengthen the flow, by increasing its mean, near-surface, kinetic energy and raising isopycnals, the latter building up available potential energy (APE). The baroclinic instability that takes place in late-July and early-August releases APE, thereby generating the SMC meanders.1

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Collaborative Observations of Boundary Currents, Water Mass Variability, and Monsoon Response in the Southern Bay of Bengal

Cited by 27 publications

References 31 publications

OceanGliders: A Component of the Integrated GOOS

OceanGliders: A Component of the Integrated GOOS

Equatorial Circulation in the Western Indian Ocean During Onset of the 2018 Summer Monsoon and Links to the Bay of Bengal

Dynamics of summer monsoon current around Sri Lanka

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