Feedbacks of CaCO3 dissolution effect on ocean carbon sink and seawater acidification: a model study

• Published in: Environmental Research Communications
• Main Authors: Han Zhang, Kuo Wang, Gaofeng Fan, Zhengquan Li, Zhenyan Yu, Jiu Jiang, Tao Lian, Guolin Feng
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publishing 2023
• Subjects: CaCO3 dissolution effect; ocean carbon sink; ocean acidification; carbon cycle modelling; carbon cycle-climate feedback; Environmental sciences; GE1-350; Meteorology. Climatology; QC851-999; Indian; Pacific; Ocean acidification
• Online Access: https://doi.org/10.1088/2515-7620/aca9ac; https://doaj.org/article/24e82bfd31c44af984acc75a843a23c6

The oceanic absorption of atmospheric CO _2 acidifies seawater, which accelerates CaCO _3 dissolution of calcifying organisms, a process termed dissolution effect. Promoted CaCO _3 dissolution increases seawater ALK (alkalinity), enhancing ocean carbon sink and mitigating ocean acidification. We incorporate different parameterizations of the link between CaCO _3 dissolution and ocean acidification into an Earth System Model, to quantify the feedback of the dissolution effect on the global carbon cycle. Under SRES A2 CO _2 emission scenario and its extension with emissions of 5,000 PgC in ∼400 years, in the absence of the dissolution effect, accumulated ocean CO _2 uptake between year 1800 and 3500 is 2,041 PgC. The consideration of the dissolution effect increases ocean carbon sink by 195–858 PgC (10%–42%), and mitigates the decrease in surface pH by 0.04–0.17 (a decrease of 10%–48% in [H ^+ ] (hydrogen ion concentration)), depending on the prescribed parameterization scheme. In the epipelagic zone, relative to the Arc-Atlantic Ocean, the Pacific-Indian Ocean experiences greater acidification, leading to greater dissolution effects and the resultant stronger feedbacks on ocean carbon sink and acidification in the Pacific-Indian Ocean. Noteworthy, the feedback of dissolution effect on ocean carbon sink can be comparable with or stronger than the feedback from CO _2 -induced radiative warming. Our study highlights the potentially critical role played by CaCO _3 dissolution effect in the ocean carbon sink, global carbon cycle and climate system.