Séminaire
Ocean acidification is the on-going decrease in the pH of the Earth's oceans caused by the uptake of carbon dioxide (CO2) from the atmosphere. In addition to this, enhanced anthropogenic processes, such as acidic aerosols, discharge of acidic effluents, further enhance rate of acidification. The Bay of Bengal is closed with land mass from the South and Southeast Asia where rapid increase in anthropogenic activities were noticed in the recent decades. In order to examine impact of enhanced aerosol contribution to atmosphere on ocean acidification, time-series observations and models studies were conducted for past two decades. Based on the observations conducted between 1991 and 2011 during winter and spring (February-May), when dominant terrestrial winds prevail, suggested that significant decrease in pH and increase in pCO2 levels (by 3 to 5 times) in the northern compared to southern Bay of Bengal. The seasonal trends of pCO2 derived from multi linear regression model suggested that the rate of increase in pCO2 is higher during January to May (3-5 matm/month) compared to other seasons (1-2 matm/y) in the northern Bay between 1997 and 2014. On the other hand, the annual growth rate of pCO2 was also higher in the northern Bay (2.2 matm/y) compared to southern Bay (1.2 matm/y). The increase in pCO2 levels were in agreement with recent increase in sulfate and nitrogen aerosol loadings over northern Bay of Bengal from the Indo-Gangetic Plain and Southeast Asia during winter and spring and also increased industrialization and fertilizer consumption over Indian subcontinent. As a result, the Bay of Bengal, which was previously considered as a significant sink for atmospheric CO2,now seems to have turned into a region of CO2 source to atmosphere. During this talk, the results from both observations and model will be presented and the on-going work in this region will also be discussed.