Modeling evidence for large, ENSO-driven interannual wintertime AMOC variability

Recently established North Atlantic ocean observing arrays, such as RAPID, have revealed a large degree of high-frequency (sub-annual), wind-driven variability in the Atlantic Meridional Overturning Circulation (AMOC). Climate modeling studies of the AMOC, however, have traditionally focused on the low-frequency variability of the annual mean AMOC, with an emphasis on multi-decadal and longer time-scale variability. Thus, less is known about the degree to which sub-annual, wind-driven AMOC variability is purely stochastic in nature or whether it is quasi-predictable via links to large-scale modes of internal variability, such as the El Nin o-Southern Oscillation (ENSO). Analyzing long control integrations of the Community Earth System Model, we here show the existence of a robust leading mode of high-frequency variability in the wintertime AMOC that is distinct from the leading mode of the annual mean. We further show that this mode of variability is significantly linked to ENSO via surface wind-stress anomalies associated with the North Atlantic Oscillation (NAO). Improving our understanding of the drivers of high-frequency AMOC variability will aide in our ability to distinguish anthropogenic trends from internal variability in the ongoing AMOC observational records.