Circulation in the Gulf of Khambhat—A Lagrangian Perspective

Abstract

The circulation of the Gulf of Khambhat (GoK) is studied from a Lagrangian point of view using a 2D numerical model. The model-predicted tide elevation and current speed are in agreement with the observations. Seasonal variations of advection of particles are simulated by releasing 237 particles homogeneously distributed over the Gulf. After one month of simulation, no particles escaped from the GoK except a few from the southern GoK during southwest monsoon (June–September), and the advection of particles was at its maximum in the northern part. Residual eddies are present inside the GoK during the northeast (October–January) and southwest monsoon seasons. Gulf circulation is studied with the combined forcing of tide and wind for different tidal conditions, which had noticeable seasonal difference. The maximum simulated current speeds of 3.4 and 2.8 m/s are noticed during southwest monsoon near to Bhavnagar and Dahej respectively, where the tide elevations are maximum indicating that GoK is a tide-dominated system. A seasonal barrier could be found in the southern Gulf, which not only makes the Gulf circulation distinct from that of the Arabian Sea (AS), but also restricts water-mass exchange between the Gulf and AS during ebb condition. As the Gulf is a dump yard for anthropogenic wastes, the present study puts forward an effort to determine the fate of the waste from a hydrodynamic point of view.

Potential Plastic Accumulation Zones in the Indian Coastal Seas

“…The GoKB is characterized by a funnel-shaped indentation, shallow depth (maximum 30 m), and a large tidal flat. The Lagrangian modeling studies showed that the particles released into the Gulf do not leave the system except for a few particles from the south of the region, suggesting restricted water-mass exchange between the Gulf and the AS (Mitra et al, 2020). Gujarat accounts for around 65% of the total plastic production of India.…”