Analyzing upper ocean variability of the Chlorofluorocarbons in the Indian Ocean using regional high-resolution ocean biogeochemical modeling

Abstract

A regional coupled ocean-biogeochemical modeling experiment is carried out over the Indian Ocean region (covering the Arabian Sea and Bay of Bengal) to generate high-resolution gridded data of Chlorofluorocarbons (CFC11 and CFC12) for the period 1999–2017. The results show that model realistically simulates hydrography of the region. It is found that western part of the Arabian Sea (AS) shows higher CFC concentration as compared to the eastern part. In the Bay of Bengal (BoB) region, the CFC decreases from north to south. The highest (lowest) surface CFC concentration in the AS and BoB is found in the winter (monsoon) season. The results indicate that while the near-surface CFC concentration of the BoB remains higher as compared to the AS, in the sub-surface (e.g., below 70–80 m depth), reverse is true. The AS region exhibits higher interannual CFC variability as compared to the BoB region. The CFC concentration over these regions decreases with time, albeit at a faster rate in the BoB region. The quantitative evaluation of the local inventories of CFC11 concentration is carried out in terms of penetration depth variability. The results indicate significant influence of ENSO on the CFC concentration of AS and BoB.