Arabian Sea records higher salinity than the Bay of Bengal because

The Arabian Sea exhibits significantly higher salinity compared to the Bay of Bengal due to a combination of high evaporation rates and minimal freshwater input. In the Arabian Sea, evaporation exceeds precipitation and river runoff, leading to a net loss of freshwater and a concentration of salts [2]. Conversely, the Bay of Bengal receives massive amounts of freshwater from major river systems like the Ganga, Brahmaputra, and Irrawaddy, which significantly dilutes its surface waters [3]. Additionally, the Bay of Bengal experiences higher precipitation, which further lowers its salinity to around 31 ppt, whereas the Arabian Sea maintains higher levels due to its location adjacent to arid regions with low humidity [1]. This contrast is a fundamental feature of the northern Indian Ocean's hydrography, where the Arabian Sea acts as a concentration basin and the Bay of Bengal as a dilution basin.

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > The Arabian Sea Surface Has Higher Salinity > p. 358
2. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 33: Ocean temperature and salinity > Indian Ocean > p. 519
3. [3] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 26: Tropical Cyclones > Higher Stratification In The Bay Of Bengal > p. 359