Examining an ensemble of high‐resolution ((1/12)°) 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 (∼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.

To understand the atmospheric response to a midlatitude oceanic front, this paper uses a quasigeostrophic (QG) model with moist processes. A well-known, three-level QG model on the sphere has been modified to include such processes in an aquaplanet setting. Its response is analyzed in terms of the upper-level atmospheric jet for sea surface temperature (SST) fronts of different profiles and located at different latitudes.When the SST front is sufficiently strong, it tends to anchor the mean atmospheric jet, suggesting that the jet's spatial location and pattern are mainly affected by the latitude of the SST front. Changes in the jet's pattern are studied, focusing on surface sensible heat flux and on moisture effects through latent heat release. It is found that latent heat release due to moist processes is modified when the SST front is changed, and this is responsible for the meridional displacement of the jet. Moreover, both latent heat release and surface sensible heat flux contribute to the jet's strengthening. These results highlight the role of SST fronts and moist processes in affecting the characteristics of the midlatitude jet stream and of its associated storm track, particularly their positions.

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