The thermohaline circulation (THC) response to ice sheet removal and quadrupling of atmospheric CO2 in a coupled model and the equilibrium thermal structure are examined. After THC weakening, diffusion of heat and salt to the northern North Atlantic at deep layers increases the temperature and salinity there, in response to CO2-quadrupling. Resulting convective instability induces the exchange of warmer, saltier water in deep layers and cooler, fresher water near the surface. This contributes to a gradual increase in the THC intensity, culminating in its complete and rapid recovery due to positive haline feedback overcoming negative thermal feedback on the THC. Removal of ice sheets prolongs the overall recovery and strengthens the final THC due to precipitation changes over the northern North Atlantic and Labrador Sea. Bottom water and high-latitude sea-surface temperatures are higher without ice sheets, leading to a smaller meridional temperature gradient as indicated by Cenozoic reconstructions.