Abstract Changes in the Atlantic Meridional Overturning Circulation (AMOC) are believed to have affected the cycling of carbon isotopes in both the ocean and the atmosphere. However, understanding how AMOC changes of Dissolved Inorganic Carbon (DIC) distributions in the ocean is limited, since models do not typically decompose the various processes that affect . Here, a new decomposition is applied to idealized simulations of an AMOC collapse, both for glacial and preindustrial conditions. The decomposition explicitly calculates the preformed and regenerated components of and separates between physical and biological effects. An AMOC collapse leads to a large and rapid decrease in in the North Atlantic, which is due to, in about equal parts, accumulation of remineralized organic matter and changes in preformed , both in glacial and preindustrial simulations. In the Pacific, Indian, and Southern Oceans increases by a smaller magnitude. This increase is dominated by changes in preformed in the glacial simulation and remineralized in the preindustrial simulation. An extensive evaluation of the decomposition shows that its errors are small in most cases, especially for large basin‐wide changes, whereas for small, local or global changes errors can be substantial. In contrast, approximations of the remineralized component based on Apparent Oxygen Utilization have large errors in most cases and are generally unreliable because they include contributions from oxygen disequilibrium.
A. Schmittner (Mon,) studied this question.