loading page

Understanding the seasonality, trends and controlling factors of Indian Ocean acidification over distinctive bio-provinces
  • +3
  • Vinu Valsala,
  • Sreeush M G,
  • Kunal Chakraborty,
  • Aditi Deshpande
Indian Institute of Technology Delhi India

Corresponding Author:[email protected]

Author Profile
Vinu Valsala
Indian Institute of Tropical Meteorology India
Author Profile
Sreeush M G
Centre for Climate Physics Institute for Basic Science (IBS) Busan Republic of Korea
Author Profile
Indian Institute of Tropical Meteorology India
Author Profile
Kunal Chakraborty
Indian National Center for Ocean Information Services,Indian Institute of Engineering Science and Technology, Shibpur (Formerly Bengal Engineering & Science University, Shibpur)
Author Profile
Aditi Deshpande
Department of Atmospheric and Space Sciences Savitribai Phule Pune University India
Author Profile


The Indian Ocean (IO) is witnessing acidification as a direct consequence of the continuous rising of atmospheric CO2 concentration and indirectly due to the rapid ocean warming, which disrupts the pH of the surface waters. This study investigates the pH seasonality and trends over various bio-provinces of the IO and regionally assesses the contribution of each of its controlling factors. Simulations from a global and a regional ocean model coupled with biogeochemical modules were validated with pH measurements over the basin, and used to discern the regional response of pH seasonality (1990-2010) and trend (1961-2010) in response to changes in Sea Surface Temperature (SST), Dissolved Inorganic Carbon (DIC), Total Alkalinity (ALK) and Salinity (S). DIC and SST are significant contributors to the seasonal variability of pH in almost all bio-provinces. Total acidification in the IO basin was 0.0675 units from 1961 to 2010, with 69.3% contribution from DIC followed by 13.8% contribution from SST. For most of the bio-provinces, DIC remains a dominant contributor to changing trends in pH except for the Northern Bay of Bengal and Around India (NBoB-AI) region, wherein the pH trend is dominated by ALK (55.6%) and SST (16.8%). Interdependence of SST and S over ALK is significant in modifying the carbonate chemistry and biogeochemical dynamics of NBoB-AI and a part of tropical, subtropical IO bio-provinces. A strong correlation between SST and pH trends infers an increasing risk of acidification in the bio-provinces with rising SST and points out the need for sustained monitoring of IO pH in such hotspots.