The stability of the thermohaline circulation in global warming experiments ...

• Main Authors: Schmittner, Andreas, Stocker, Thomas
• Format: Article in Journal/Newspaper
• Language: English
• Published: University of Bern 1999
• Subjects: North Atlantic Deep Water; North Atlantic
• Online Access: https://dx.doi.org/10.48350/158883; https://boris-portal.unibe.ch/handle/20.500.12422/43464

A simplified climate model of the coupled ocean–atmosphere system is used to perform extensive sensitivity studies concerning possible future climate change induced by anthropogenic greenhouse gas emissions. Supplemented with an active atmospheric hydrological cycle, experiments with different rates of CO2 increase and different climate sensitivities are performed. The model exhibits a threshold value of atmospheric CO2 concentration beyond which the North Atlantic Deep Water formation stops and never recovers. For a climate sensitivity that leads to an equilibrium warming of 3.6°C for a doubling of CO2 and a rate of CO2 increase of 1% yr−1, the threshold lies between 650 and 700 ppmv. Moreover, it is shown that the stability of the thermohaline circulation depends on the rate of increase of greenhouse gases. For a slower increase of atmospheric pCO2 the final amount that can be reached without a shutdown of the circulation is considerably higher. This rate-sensitive response is due to the uptake of heat and ...