Equilibrium integrations with the three‐dimensional Hamburg ocean carbon cycle circulation model show the effect of a Southern Ocean surface outcrop that is closed off for gas exchange with the atmosphere and export production of particulate organic carbon and CaCO3south of 32.5 °S. For such a close‐off, the northern Atlantic outcrop assumes a greater degree of control of atmospheric CO2partial pressure. Contrary to expectations, the atmospheric pCO2increases compared to a control run without close‐off. Maximizing the nutrient utilization in the North Atlantic can compensate for this increase. However, it does not draw down the pCO2to glacial