There have been many studies on iron as a limiting nutrient for productivity in the World Ocean, but only a few studies have been done in the Arabian Sea on iron limitation. Sensitivity of primary productivity, chlorophyll, nitrate, $\rm{pCO_{2}}$ and carbon flux in the Arabian Sea to one of the parameters related to iron limitation has been investigated using a three-dimensional coupled biogeochemical model (TOPAZ) embedded in Modular Ocean Model (MOM) in the global domain, for climatology and interannual variability. Initially, the model results are evaluated for many of the biogeochemical components using data from World Ocean Atlas, satellites and cruises in the Arabian Sea. It is noticed that model results capture spatial and temporal variations of some of the biogeochemical components and fluxes in the north Indian Ocean. Subsequently, it is shown that micronutrient iron plays a significant role on the growth of phytoplankton, utilization of nutrients, $\rm{pCO_{2}}$ in the ocean and carbon flux across the air–sea interface in north and north-west regions of the Arabian Sea.