Cause and impact of Andaman Sea's salinity variability: A modeling study

Abstract

The Andaman Sea is an important and strategic region for India, both from a security and conservation viewpoint. Documenting the spatiotemporal variability of salinity is fundamental to understanding this region's dynamics. We studied the Andaman Sea's seasonal and inter-annual salinity variability during the Boreal summer (JJAS) using NEMO reanalysis data (1993–2018). Analysis of river influx, precipitation, Empirical Orthogonal Functions of the salinity fields, numerical particle trajectory experiments, and statistical significance tests were conducted to understand the causal factors and impact of the Andaman Sea's salinity variability. Our study shows that it is the Southwest Monsoon Current (SMC) that brings a significant influx of salinity into the Andaman Sea and governs the seasonal cycle. We also document and explain the different surface and sub-surface dynamical trends. We show that higher salinity influx to the Andaman Sea is correlated with the strength of SMC. Crucially, this study is the first-ever attempt to comprehend the salinity dynamics of the Andaman Sea utilizing both Empirical Orthogonal Function (EOF) analysis and particle trajectories. We also note the reported reduction in shark catch and qualitatively analyze its relation to the seasonal salinity cycle, motivating the need for further physical-biological combined studies of the region.