The North Atlantic represents the largest sink for atmospheric CO₂ in the northern hemisphere, yet little is known about its temporal variability. Here we report observations from a long time-series of upper ocean inorganic carbon parameters from the subtropical North Atlantic near Bermuda that indicate substantial variability in the North Atlantic carbon sink. We find that the variability in carbon dynamics at this site is largely driven by variations in winter mixed layer depths and sea-surface temperature (SST) anomalies, whose variability are significantly correlated with the North Atlantic Oscillation (NAO).Since variations in mixed layer depths and SST tend to occur in basin-wide coordinated pattern associated with NAO, it is feasible that the entire North Atlantic might vary in concert with Bermuda, resulting in a variability of the strength of the North Atlantic carbon sink of about +/- 0.3 PgC \yrr (1 Pg = 10¹⁵g), or nearly +/-50%. This extrapolation, while rather speculative, is supported by basin-wide estimates on the basis of atmospheric CO₂ inversions.