Current CaCO3 dissolution at the seafloor caused by anthropogenic CO2

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Sulpis, Olivier, Boudreau, Bernard P., Mucci, Alfonso, Jenkins, Chris, Trossman, David S., Arbic, Brian K., Key, Robert M.
• Format: Text
• Language: English
• Published: National Academy of Sciences 2018
• Subjects: Physical Sciences; Indian; Pacific; North Atlantic; Ocean acidification
• Online Access: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6243283/; http://www.ncbi.nlm.nih.gov/pubmed/30373837; https://doi.org/10.1073/pnas.1804250115

Oceanic uptake of anthropogenic CO(2) leads to decreased pH, carbonate ion concentration, and saturation state with respect to CaCO(3) minerals, causing increased dissolution of these minerals at the deep seafloor. This additional dissolution will figure prominently in the neutralization of man-made CO(2). However, there has been no concerted assessment of the current extent of anthropogenic CaCO(3) dissolution at the deep seafloor. Here, recent databases of bottom-water chemistry, benthic currents, and CaCO(3) content of deep-sea sediments are combined with a rate model to derive the global distribution of benthic calcite dissolution rates and obtain primary confirmation of an anthropogenic component. By comparing preindustrial with present-day rates, we determine that significant anthropogenic dissolution now occurs in the western North Atlantic, amounting to 40–100% of the total seafloor dissolution at its most intense locations. At these locations, the calcite compensation depth has risen ∼300 m. Increased benthic dissolution was also revealed at various hot spots in the southern extent of the Atlantic, Indian, and Pacific Oceans. Our findings place constraints on future predictions of ocean acidification, are consequential to the fate of benthic calcifiers, and indicate that a by-product of human activities is currently altering the geological record of the deep sea.