Elevated Acidification Rates Due to Deposition of Atmospheric Pollutants in the Coastal Bay of Bengal

Abstract

Absorption of atmospheric CO 2 is lowering the pH of surface-ocean at the rate of 0.0015 ± 0.0005 units per year (Bates et al., 2014;Sutton et al., 2017) in the global ocean. The rate of acidification is reported as higher in the coastal than offshore region due to the proximal multiple human activities that modify the carbonate equilibria (e.g., Cai et al., 2011). Deposition of sulfate and nitrate aerosols, formed from fossil fuel and biomass burning, may further decrease pH of surface ocean (Doney et al., 2007;Mackenzie, 1995;Schlesinger, 1997).The Bay of Bengal (BoB or northeastern Indian Ocean) is the best suited region to study impact of atmospheric aerosols deposition on surface ocean acidification due to its proximity to populated areas, this region is under the influence of multitude human activities of the world's most populated region (Boblme, 2014). Zhang and Reid (2010) reported higher levels of aerosol optical depth (AOD) over the BoB and the rate of increase is the highest compared to elsewhere in the world. Recently Yadav et al. (2021) estimated higher rate of increase in anthropogenic aerosols over the northwestern and western coastal BoB (0.006-0.01/yr respectively) between 2001 and 2019 than earlier report (Zhang & Reid, 2010). Based on atmosphere-ocean couple model, Doney et al. (2007) found that atmospheric deposition of pollutants in the open sea region of BoB is decreased pH of surface-ocean by 0. 003 between 1990003 between and 2000003 between . Sarma et al. (2015 reported rapid increase in acidification in the western coastal BoB, based on data collected during 1991 and 2011, due to deposition of atmospheric pollutants. Since this study is based on two snapshot measurements, it is unclear the longterm variability in pH and potential reasons responsible for its variability. In order to examine the influence of atmosphere-ocean interactions on long-term variability in ocean acidification, time-series observations were conducted between 2007 and 2018 in the BoB. Based on this data, we would like to evaluate the (a) rate of acidification in the coastal BoB, (b) long-term variability in composition of atmospheric aerosols, and (c) impact of deposition of atmospheric pollutants on coastal water pH through laboratory experiments.

Distribution and Production of N2O in the Subtropical Western North Pacific Ocean During the Spring of 2020

“…Atmospheric dust deposition, the vehicle for AND, directly acidifies the seawater. Nitrification elevated by AND-driven productivity also provides a greater H + concentration in the water column, leading to ocean acidification (negative feedback) (Doney et al, 2007;Sarma et al, 2021). Therefore, AND exerts a combination of positive and negative effects on N 2 O production in STWNPO.…”

Air‐Sea Fluxes of CO2 in the Indian Ocean Between 1985 and 2018: A Synthesis Based on Observation‐Based Surface CO2, Hindcast and Atmospheric Inversion Models

“…The lack of primary productivity trends due to an increase in the deposition of nutrients from the atmosphere was reported (Sarma, Prasad, & Dalabehera, 2021; Sridevi et al., 2023). Rapid rate of ocean acidification was reported due to the atmospheric deposition of pollutants (Kumari, Sarma, & Dileep Kumar, 2022; Kumari, Sarma, Mahesh, & Sudheer, 2022; Sarma et al., 2015; Sarma, Krishna, et al., 2021). Therefore, the inclusion of atmospheric pollutants in the model improves the simulations of future changes in CO 2 fluxes significantly.…”

“…More recently Sarma et al (2019) reported that cyclonic eddies enhance pCO 2 levels due to upwelling in the core of the eddy while anticyclonic eddies sink for atmospheric CO 2 . Several recent investigations suggested that rapid acidification is being occurred in the BoB due to the deposition of atmospheric pollutants (Kumari, Sarma, & Dileep Kumar, 2022;Kumari, Sarma, Mahesh, & Sudheer, 2022;Sarma et al, 2015;Sarma, Krishna, et al, 2021) leading to an increase in pCO 2 levels. Unfortunately, neither GHM nor RHM has the atmospheric component to consider its impact.…”

“…Despite the importance of the Indian Ocean in the global carbon cycle, this region is poorly studied with reference to the biogeochemical cycling of carbon compared to the other two major basins. The seasonal cycle of pCO 2 and carbon fluxes was studied only in the Arabian Sea (Chakraborty et al, 2021;De Verneil et al, 2022;George et al, 1994;Goyet et al, 1998;Sarma et al, 1998Sarma et al, , 2003Sarma et al, , 2013, the BoB (Chakraborty et al, 2021;Sarma et al, 2012Sarma et al, , 2015Sarma et al, , 2020Sarma, Krishna, et al, 2021) and the south-western Indian ocean (Metzl et al, 1998) whereas the long-term variability was only recently studied in the southwestern Indian Ocean region (Metzl et al, 2022) as the other regions in the Indian Ocean was either sampled once or twice during last few decades (Sarma et al, 2013;Takahashi et al, 2009). The studies carried out in the aegis of the Joint Global Flux Study (JGOFS) and the Bay of Bengal Process Studies (BoBPS) suggested that the seasonal amplitude of pCO 2 goes beyond 200 μatm in the Arabian Sea (George et al, 1994;Goyet et al, 1998;Sarma et al, 1998Sarma et al, , 2003 and BoB (Kumar et al, 1996;Sarma et al, 2012Sarma et al, , 2015Sarma et al, , 2019.…”

Impact of atmospheric anthropogenic nitrogen on new production in the northern Indian Ocean: constrained based on satellite aerosol optical depth and particulate nitrogen levels

“…8,[34][35][36] In addition, efforts have been made to measure the chemical composition of aerosols under the aegis of several national and international programs in India. 13,14,19,23,25,32,[37][38][39][40] Combining several snapshot measurements, Srinivas and Sarin 38 estimated that dry deposition of inorganic nutrients supports $13% of the surface primary production in the Bay of Bengal (BoB) and $5% of the surface primary production in the Arabian Sea (AS) during the dry period. Similarly, Yadav et al 32 highlighted that $70% of the total suspended particulate matter (TSP) was deposited within 10 km from the coast and can support 3 to 33% of the coastal surface primary production during fall and winter seasons in the BoB.…”