SLOWING DOWN OF THERMOHALINE CIRCULATION AND CONTINENTAL MARGIN DENSE-WATER EXCHANGE MECHANISMS
A fifth very serious impact of climate change may be on ocean circulation. Palaeo-analogues and model simulations show that the Meridional Overturning Circulation (MOC) can react abruptly and with a hysteresis response, once a certain forcing threshold is crossed. Discussion on the probability of the forc-
ing thresholds being crossed during this century lead to different conclusions depending on the kind of model or analysis (Atmo- sphere-Ocean General Circulation Models, Earth systemmodels of intermediate complexity or expert elicitations) being used. Po- tential impacts associated with MOC changes within the marine
Figure 20. The Meridional Overturning Circulation plays a crucial role for life in the oceans. If this ocean conveyor belt slows down or changes as a result of melting ice and increasing ocean temperatures, the impacts on marine life may become severe.