Persistence of Arctic Ocean acidification under negative emissions

[Geoengineering News]

https://www.nature.com/articles/s41558-026-02715-9

Authors: Eike E. Köhn, Lester Kwiatkowski, Juliette Mignot, Guillaume Gastineau, Olivier Torres & James C. Orr 

06 August 2026

Abstract

Although net negative emissions of carbon dioxide (CO2) are essential to meet climate targets, little is known about how declining atmospheric CO2 levels will affect ocean acidification. Here, by analysing the acidity ([H+]) and corrosivity to aragonite (ΩArag) in eight Earth system models that made simulations under rising then falling CO2 levels, we identify the Arctic as a hotspot for delayed reversibility of ocean acidification. Under falling CO2, Arctic surface waters remain comparatively more acidic, and aragonite-corrosive conditions (ΩArag < 1) persist until atmospheric CO2 drops ~120 ppm below the threshold at which they first appeared under rising CO2. This hysteresis arises from the erosion of the natural surface-layer deficit in dissolved inorganic carbon, initially maintained by sea ice limiting air–sea gas exchange and not fully restored as sea ice recovers during CO2 decline. Thus, the Arctic Ocean experiences not only the greatest acidification but also the most delayed benefits from negative emissions.

Source: Nature Climate Change 

[Greg Rau]

“Thus, the Arctic Ocean experiences not only the greatest acidification but also the most delayed benefits from negative emissions.“

A little less acidification and delayed benefit if the negative emissions of choice is OAE in the Arctic Ocean? Model the ocean pH if the entire negative emissions were to be achieved by alkalizing the surface waters here and see what you get. I’m not saying this is feasible, but the impact of CDR on ocean chem (and bio) will depend on the method(s) used, esp if (abiotic) mCDR methods are used. 

Regards,

Greg Rau

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