The Bay of Bengal (BoB) is a unique semi-enclosed basin among the world oceans, with features such as seasonally reversing monsoon winds, frequent cyclones, freshwater
discharge from rivers, as well as intense rainfall during the monsoon seasons. It is dominated by fronts, filaments and eddies, which are strongly influenced by the
complex current patterns in the region. Horizontal advection introduces a wide range of spatial and temporal scales, in turn enhancing transport and mixing in atmosphere and
ocean. Specifically, the stirring of freshwater by upper ocean circulation influences the spatial and temporal distribution of well mixed layer in the upper ocean. The
conditions in the upper ocean is strongly influenced by the distribution of mixed layer and thereby influencing air-sea exchange processes and biological productivity.
The thesis investigates the role of relative importance of different processes which controls the upper ocean circulation and in turn the freshwater transport in the Bay of
Bengal. To achieve this goal, we use the objective framework of Lagrangian Coherent Structures (LCS), which makes use of finite time particle advection to explain observed patterns in tracer transport. Further, a detailed study of materially coherent eddies in the Bay of Bengal is conducted using the Lagrangian Averaged Vorticity Deviation (LAVD) method. An SSH-based Eulerian eddy detection method is also implemented to understand its efficacy in identifying materially coherent eddies in the BoB region.

Keywords: Bay of Bengal; LCS; Freshwater