Flows in which spatial variations in density play a dynamical role are referred to as stratified flows. The atmosphere and ocean are examples of naturally occurring background states in which density varies with height and depth, respectively. Advective stirring 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. In this thesis, advective stirring in the Bay of Bengal is investigated, followed by laboratory experiments on a fundamental study of advective stirring in an ideal stratified flow. Specifically, understanding 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 is the first goal of this study. 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. Towards the second goal of a fundamental study, experiments to understand the effect of density stratification on horizontal advective stirring on different isopycnal surfaces are being set up. The experiment involves a sphere being towed in the horizontal direction in a density stratified medium. This experiment can also be viewed as a laboratory model of oceanic or atmospheric flows past topographic features of limited horizontal extent.