Ocean Acidification

Highlights

• A coupled physical-biogeochemical model (ROMS-PISCES) has been set up for the Bay of Bengal region to emulate the carbonate chemistry of this region.
• The model has been run and rigorously evaluated using the available data sets and 8 statistical indices have been used to evaluate model skills.
• The effect of wind stress and E-P has been evaluated through two numerical experiments, which uses two different bulk formulae to calculate the wind stresses.
• The model is excellent in simulating the spatial heterogeneity and temporal variation of all the carbonate parameters thus giving a basis for further studies like the effect of physical dynamics, forecasting, etc.

Abstract

The Bay of Bengal is a semi-enclosed ocean basin situated in the eastern part of the North Indian Ocean. Though the physical dynamical features of the Bay of Bengal have been studied and measured in detail, the carbonate chemistry of this basin has been less explored, and very few reliable data-sets exist. This paucity of data has emerged as a major challenge in modeling and understanding the carbonate system parameters for this region. In this study, a coupled physical-biogeochemical (ROMS-PISCES) model has been configured and run to emulate the surface carbonate system parameters (DIC, TALK, pCO2, and pH) for the Bay of Bengal region. Model skill assessment analysis has been performed using available observational data-sets. Two different numerical experiments have been performed (WB indicating the use of default bulk formulae of ROMS to calculate wind stress and WoB indicating the calculated wind stresses of QuikSCAT climatology product using different bulk formula), to understand which one reproduces the carbonate parameters better. Both the numerical experiments are rigorously compared for physical as well as carbonate system parameters. The numerical experiments have been passed through exhaustive statistical analysis by comparing it with the observed data-sets. The temperature, the primary driver affecting pH and pCO2 has been reproduced by both the experiments excellently, and the correlation value is more than 0.9 with RAMA buoy data (15o N, 90o E). The salinity, when compared with the NIOA climatology data, shows that the WoB experiment has better captured both the spatial and temporal variation of salinity. Both the numerical experiments have been compared individually with three sets of observed carbonate data. The WoB run has been found to emulate carbonate system parameters satisfactorily than the WB run. The pCO2 and pH show a good positive correlation with RAMA data and the values are 0.87, and 0.93, respectively.