Modelling tide-driven currents and residual eddies in the Gulf of Kachchh and their seasonal variability: A marine environmental planning perspective
ABSTRACT Tide-driven currents in the Gulf of Kachchh (GoK) have been studied using MIKE21 hydrodynamic model. The results are validated with measured currents for three different periods characterized by different wind fields. Comparison of model results showed very good agreement with the measured currents. The study suggests that though the currents of GoK are predominantly tide-driven, they respond significantly to the seasonally changing wind system. Strong southwesterly winds enhance the flood tidal currents by about 20% but reduce the ebb tidal currents by about 20% during June–July. The currents intensify during NE monsoon period as well as SW monsoon period when the winds become stronger. However, the currents are comparatively weak during pre-monsoon transition. Irregular topography of the western gulf slows down the tidal wave propagation and induces a phase shift. Tidal residual currents computed from the model results exhibit the presence of three eddies in the western gulf. The tide–topography interaction could be responsible for generating eddies in the residual flow field. It is possible that these eddies could effectively decrease the flushing rate of materials discharged in the upstream gulf, and subsequently increase their residence time. The hydrodynamic modelling setup forms a base for future ecological modelling endeavours planned for the gulf in order to reduce stress on the ecosystem especially in the sensitive areas such as the Marine National Park and Marine Sanctuary.
- SourceAvailable from: Grinson George[Show abstract] [Hide abstract]
ABSTRACT: A two-dimensional hydrodynamic and particle tracking model was used to estimate the dispersion and retention of barnacle larvae from their possible spawning sites in a tropical monsoon-influenced estuarine system (central west coast of India). Validation of the hydrodynamic simulations yielded a good match with field measurements. The pattern of larval dispersal in the region varied with the winds and currents. The seasonal changes in abundance could be attributed to physical forcing and weather conditions. The extent of barnacle larval dispersal from spawning sites varied from 10 to 78 km for different sites and seasons. During a 24-h cycle, the larval abundance showed one to two peaks in the estuarine area. The increased larval abundance is favored by the flood currents, pushing the larvae into the estuary. Physical forcing in the region helps in transport of the larvae from their spawning sites hugging to the coast and contributing to the population within the estuary. Field observations and numerical experiments suggest the occurrence of higher larval abundance in the estuary during post-monsoon. The dispersal pattern indicated that the barnacle population present in the estuary is well mixed, and with a seasonally changing pattern.Journal of Oceanography 08/2013; 69(4):451-466. · 1.46 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The present study is an attempt towards understanding the sediment routing system in the semi-arid margin of the Gulf of Kachchh, which is one of the largest macrotidal regimes in the northern Arabian Sea. Investigations based on heavy minerals, clay minerals, mineral magnetic properties and sediment geo-chemistry indicated that there are three major sources of sediments contributing to the Gulf of Kachchh basin: (1) Indus River, (2) Kachchh mainland coastal rivers and (3) the Saurashtra peninsular coastal rivers. The flanks of northern and southern coast of western Gulf of Kachchh show dominant signatures of Kachchh mainland/Saurashtra peninsular provenance. In contrast, the eastern Gulf of Kachchh coast bearing fine grained sediments shows dominant Indus River Provenance. Although ephemeral in nature, the small coastal rivers of Saurashtra and Kachchh contribute significant amount of sediments to the Gulf of Kachchh coastline because of their 'dryland' nature and thus they control the coarse grained sedimentation processes.
- [Show abstract] [Hide abstract]
ABSTRACT: Present study is the coastal circulation modelling off Ratnagiri under the influence of winds and tides. A two-dimensional hydrodynamic model MIKE 21HD has been used to simulate tides and currents, and model results are in a good agreement with the measurements. In July, representing the southwest monsoon, wind is relatively strong, onshore current component is more pronounced; but, tidal variations are masked to a great extent by the wind driven circulation. Relatively stronger winds of the order of 8 m/s, persisted for a longer period, and that contributed to the southward flowing coastal current which is more consistent in its direction and magnitude. Meridional current has a prominent southward direction with a maximum alongshore speed of ~0.41 m/s. Zonal current is too weak to have a considerable impact on the circulation pattern. Prominent circulation is southward, irrespective of the seasons.Indian Journal of Geo-Marine Sciences 02/2014; 43(4):481-488. · 0.56 Impact Factor