Role of Andaman and Nicobar Islands in eddy formation along western boundary of the Bay of Bengal

Abstract

Eddies along western boundary of the Bay of Bengal (WBoB) play an important role in regulating regional climate and marine productivity of the north Indian Ocean. In this paper, role of Andaman and Nicobar islands (ANIs) in the formation of eddies along the WBoB is studied using an ocean general circulation model. Our analysis shows that, in the absence of ANIs, there is a significant reduction in the total number of mesoscale eddies in this region. The impact is particularly evident for the cyclonic eddies as a reduction of ~50% can be noticed in the absence of the islands. In contrast, influence of ANIs on anticyclonic eddies is not homogeneous in the WBoB; while absence of ANIs significantly increases anticyclonic eddies in the central part of the WBoB, a decrease can be noticed in the southern part. We further show that the reduction in number of cyclonic eddies along the WBoB is primarily driven by reduced baroclinic and barotropic instabilities. This process is more conspicuous during winter (October–January) season compared to summer (June–September) and spring (February–May) seasons.

Seasonality of surface stirring by geostrophic flows in the Bay of Bengal

“…Interestingly, these coherent westward tilting structures, or wave packets, also appear to exhibit episodic eastward migration with systematic positive (orange) and negative ( Another common feature which we observe is the presence of shorter time scale (< 30 days) eddies or waves around 94 ∘ E-97.625 ∘ E, i.e. near the Irrawaddy river basin, through out the year (Mukherjee et al, 2019). We have also constructed Hovmöller plots of the zonal velocity with respect to latitude (not shown), these showed a fairly mixed behavior with sporadic instances of northward and southward tilts.…”

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

“…As internal tides propagate large distances through the varying oceanic conditions, they lose coherency with the barotropic tides and become incoherent (Nash, Shroyer, et al, ). Previous studies have shown strong activity of mesoscale eddies in the BoB (Chen et al, ; Mukherjee et al, ). Hence, the interaction of long‐range propagating internal tides with varying mesoscale fields could be important in the BoB.…”

Progress in understanding of Indian Ocean circulation, variability, air–sea exchange, and impacts on biogeochemistry

“…The Kelvin waves then trigger southwestward-propagating Rossby waves, which result in large mesoscale structures in the bay (X. . The Andaman Islands and Nicobar Islands are also shown to be very important for the generation of these eddies; without these islands the number of eddies would have reduced to almost half in the western bay of Bengal (Mukherjee et al, 2019). These eddies provide much of the horizontal stretching and stirring of the tracers, including those relevant to the ecosystems.…”