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With the role of surface winds in the generation of ocean waves, secondary microseisms induced by ocean wave‐wave interactions represent a unique interconnection between the solid Earth, the ocean and global atmospheric circulation patterns. In this study, temporal changes in the ocean generated seismic wavefield in Northeast Atlantic are monitored offshore West of Ireland using ocean bottom seismometers located on top of a thick sedimentary basin. Comparisons with numerical seismic simulations and ocean wave model hindcast data suggest those variations are correlated with changing patterns in ocean wave‐wave interactions closely linked to secondary microseism generation areas. Here we show how those changes, accentuated by the specific structure of the Irish offshore margin, reveal the signature of the North Atlantic Oscillation (NAO) in the Earth's background seismic wavefield. In the North Atlantic, secondary microseism sources likely fluctuate with the changing storm track in response to variations in the NAO. Plain Language Summary: Ocean waves continuously generate seismic waves at the seafloor that are observed all over the world. In this study, we show how such vibrations recorded at the seafloor offshore West of Ireland are sensitive to long term weather and climate fluctuations in the Northeast Atlantic. Combining ocean wave and seismic simulation models with observations, we show that the North Atlantic Oscillation (NAO) climate index is hidden in the seismic records. Key Points: Fluctuating secondary microseism sources in the Northeast Atlantic highlight the variability of the NAO climate index through timeAmbient seismic noise recorded at key locations on the seafloor exhibits detailed sensitivity to global atmospheric circulation patternsTemporal changes in the modal excitation of secondary microseism Rayleigh waves reveal changing patterns in local ocean wave‐wave interactions [ABSTRACT FROM AUTHOR]