Modeling the seasonal variability and the governing factors of Ocean Acidification over the Bay of Bengal region

TL;DR

This study models the seasonal variability of ocean acidification in the Bay of Bengal, identifying key factors like SST, SSS, and DIC that influence pH levels and highlighting the region's complex acidification dynamics.

Contribution

It provides a detailed analysis of the governing factors affecting pH seasonality in the Bay of Bengal using sensitivity experiments, emphasizing the region's unique stratification effects.

Findings

SST, SSS, and DIC are primary drivers of pH variability.

Stratification and barrier layer thickness influence surface pH.

Northern Bay of Bengal is more alkaline than the southern part.

Abstract

The Bay of Bengal (BoB) is a high recipient of freshwater flux from rivers and precipitation, making the region strongly stratified. The strong stratification results in a thick barrier layer formation, which inhibits vertical mixing making this region a low-productive zone. In the present study, we attempt to model the pH of the BoB region and understand the role of different governing factors such as sea-surface temperature (SST), sea-surface salinity (SSS), dissolved inorganic carbon (DIC), and total alkalinity (TALK) on the seasonality of sea-surface pH. We run a set of sensitivity experiments to understand the role of each of the governing factors. The results show that the SST, SSS, and DIC are the principal drivers affecting the sea-surface pH, while TALK plays a buffering role. The SST and DIC are consistently found to be opposite to each other. The pre-monsoon season (MAM) has shown to have an almost equal contribution from all the drivers. In the pre-monsoon season, the SST and DIC are balanced by TALK and SSS. The role of SSS is significantly dominant in the second half of the year. Both SST and SSS counter the role of DIC in the southwest monsoon season. The strong stratification plays an essential role in modulating the pH of the BoB region. The thickness of the barrier layer formed in the sub-surface layers positively affects the sea-surface pH. The northern BoB is found to be more alkaline than the southern BoB. Our study highlights the complexity of ocean acidification in the BoB region compared to the other part of the world ocean.