Spatiotemporal Patterns of Chaos in the Atlantic Overturning Circulation

Examining an ensemble of high-resolution ((1/ 12)degrees) North Atlantic ocean simulations, we provide new insights into the partitioning of the Atlantic Meridional Overturning Circulation (AMOC) variability between forced and intrinsic at low-frequency (2-30 years). We highlight the existence of a basin-scale intrinsic mode that shares similarities with the atmospherically forced signal. The RAPID-MOCHA-WBTS array is found to be part of this mode, such that we ascribe about 0.9 Sv (50% in our configuration) of its interannual variability as intrinsic. At decadal time scales, intrinsic variability is rather small (similar to 0.2 Sv) compared to the recently observed 2- to 3-Sv AMOC downturn. This downturn is thus unlikely to be induced by locally generated intrinsic ocean dynamics. We interpret this intrinsic variability as chaotic, that is, somewhat unpredictable, providing an estimation of the quantitative accuracy of AMOC variability within eddy-resolving numerical models.