Considerations for hypothetical carbon dioxide removal via alkalinity addition in the Amazon River watershed

• Main Authors: Mu, Linquan, Palter, Jaime B., Wang, Hongjie
• Format: Text
• Language: English
• Published: 2023
• Subjects: North Atlantic
• Online Access: https://doi.org/10.5194/egusphere-2022-1505; https://egusphere.copernicus.org/preprints/2023/egusphere-2022-1505/

The Amazon River plume plays a critical role in shaping the carbonate chemistry over a vast area in the western tropical North Atlantic. We explore a thought experiment of ocean alkalinity enhancement (OAE) via hypothetical quicklime addition in the Amazon River watershed, examining the response of carbonate chemistry and air-sea carbon dioxide flux to the alkalinity addition. Through a series of sensitivity tests, we show that the detectability of the OAE-induced alkalinity increment depends on the perturbation strength (or size of the alkalinity addition, ΔTA) and the number of samples: there is a 90 % chance to meet a minimum detectability requirement with ΔTA > 15 μ mol kg -1 and sample size > 40, given background variability of 15–30 μ mol kg -1 . OAE-induced p CO 2 reduction at the Amazon plume surface would range between 0–25 μ atm when ΔTA = 20 μ mol kg -1 , decreasing with increasing salinity. Adding 20 μ mol kg -1 of alkalinity at the river mouth could elevate the total carbon uptake in the Amazon River plume by 0.07–0.1 MtCO 2 month -1 . Such thought experiments are useful in designing minimalistic field trials and setting achievable goals for monitoring, reporting, and verification purposes.