Impacts of simulated coastal ocean alkalinity enhancement on the seasonal carbon cycle in European waters under a low- and a high-emission scenario

One potentially scalable method to remove CO 2 from the air is ocean alkalinity enhancement (OAE), which works to lower the ocean's CO 2 partial pressure ( p CO 2 ) and accelerate CO 2 sequestration and durable storage. This study explores how OAE might affect the seasonal carbon cycle, which plays a key role in the ocean's annual CO 2 uptake. By analysing Earth System Model simulations of OAE implemented continuously at the European coastline under low and high emissions, it was found that: (a) due to surface alkalinity retention, OAE reduces ocean p CO 2 most strongly in summer, turning the region into a year-round carbon sink; (b) the strongest air-sea CO 2 uptake enhancement takes place in winter; (c) the ocean's carbon sink is increased more strongly in SSP3-7.0 than in SSP1-2.6 due to a lower buffering capacity.