Predictability of the Atlantic overturning circulation and associated surface patterns in two CCSM3 climate change ensemble experiments

After taking into account both the mean and spread about the mean of the forecast distributions, and allowing for the possibility of time evolving modes, the natural variability of the AMOC is found predictable for about a decade; beyond that range the forced predictability resulting from greenhouse gas forcing becomes dominant.

The upper-500m temperature in the North Atlantic is even more predictable than the AMOC by several years. This predictability is associated with subsurface and sea surface temperature (SST) anomalies that propagate in an anticlockwise direction along the subpolar gyre and which tend to be prominent during the 10 years following peaks in the amplitude of AMOC anomalies. Predictability in the North Atlantic SST mainly resides in the ensemble mean signals after 3-4 forecast years.