Exploring concentration of chlorophyll-a, SST and salinity variability over the Bay of Bengal: Integrating ROMS model and in-Situ observations

Abstract

This study is to replicate the oceanic circulation pattern in the Bay of Bengal (BoB) spanning from 1998 to 2014 using Regional Ocean Modelling Systems (ROMS). The model's performance in seizing the ocean's most vital features, such as sea-surface temperature (SST), salinity, chlorophyll-a (Chl-a) concentration, and surface currents, has been analyzed. The model represents spatial dynamics, with seasonal change progressing from the northeast to the southwest within the Bay of Bengal. From MAM, the southern BoB and central region of BoB areas demonstrate warming trends, whereas the SST increase in the northern BoB is a result of JJAS. These shifts are a result of changes in sun irradiation, mixed layer depth variations, and freshwater influx. The model shows relative alignment with the observed data, except during JJAS, where higher SSTs were observed. These higher SSTs are likely due to the intricate interactions involving monsoon-driven atmospheric variability, which impacts surface heating and freshwater influx, as well as unresolved model parameters related to vertical mixing and heat flux processes. The research work to be done requires quantification of the model's performance, and the statistical methods yield a moderate correlation for both SST and concentration of Chl-a. A variety of factors, including upwelling, coastal dynamics, and atmospheric processes, can explain these patterns. The paper emphasises the idea of the complex character of coastal processes, and it emphasises the importance of adequate representation of these phenomena in the models. The modelling of concentrations of Chl-a also exhibits a distinct seasonal trend, and the model duplicates essential features but shows biases near the coastal areas, likely due to limitations in the model's horizontal resolution, the treatment of freshwater input, and the representation of coastal upwelling processes. Positive and negative anomalies of the SST and the concentration of Chl-a are connected with the complex interaction of ocean-atmosphere systems, thereby demonstrating the interplay of different factors. Fundamentally, the research points to the significance of faithful simulation of ocean circulation and coupled elements for the proper assessment of the highly complicated BoB dynamics.