The manuscript tests the effect of changes in atmospheric CO2 on oceanic carbon uptake using a model, while keeping other parameters such as circulation, temperature, and sea ice identical. The broad conclusions are physically sensible: lower atmospheric CO₂ reduces the air–sea gradient, uptake declines rapidly, and the resulting DIC anomaly is redistributed along upper-ocean ventilation pathways. I suggest some revisions to improve clarity.

The manuscript should explicitly define “mitigation”, as this word can be misleading. As implemented here, mitigation is not an emissions intervention but a prescribed atmospheric CO₂ concentration trajectory. The model does not simulate emissions, policy actions, carbon-dioxide removal, enhanced marine productivity, or the coupled feedback of altered ocean uptake on atmospheric CO₂. This distinction is essential because different mitigation strategies could produce different ocean responses. Please define the term consistently in the abstract, introduction, and methods and consider modifying the title to describe the imposed concentration forcing accurately.

Please show the biological DIC-budget terms rather than asserting that biological differences are negligible. Enhanced biological consumption and export could lower surface-ocean pCO2, partially restore the air–sea gradient, and modify the inferred response.

Some language incorrectly implies that circulation changes between runs. Physics is identical, so mitigation does not alter circulation in this experiment. Advection-budget differences arise because the same velocity field transports different DIC distributions. Statements about “the dynamic response of ocean circulation” (line 112) should instead refer to tracer redistribution by fixed circulation.

High-latitude and boundary-current systems show the largest modeled responses, but their strong natural variability and sparse observations may obscure the mitigation signal. Because the study does not perform a signal-to-noise or time-of-emergence analysis, it cannot conclude that these signals would be detected earliest in the real ocean.

Explain exactly how the atmospheric CO₂ scenarios were constructed. The backward shifting of SSP1-1.9 and SSP1-2.6 concentration trajectories is insufficiently documented. Please provide the transformation, original and shifted years, treatment of the January 2000 transition, and complete atmospheric CO₂ time series. Clarify whether the scenarios represent lower concentrations, lower growth rates, or actual concentration declines. This information is necessary for reproducibility and interpretation.