Solar modulation of the North Atlantic Oscillation: Assisted by the tides?

Several prominent lines in the spectrum of the North Atlantic Oscillation (NAO) are here considered as resulting from solar–tidal modulation. Lines near 8.9, 7.7, and 5.8 years are proposed to be a result of energy capture from internal oscillations into periods resulting from interference of solar and tidal cycles near 11 years (solar) and at 18.61 and 4.425 years (tidal). The dominant period in the range 10–5 years, near 7.74 years, is explained as a result of lock-in of mutually supportive interference cycles; that is, the difference tones between solar cycles near 10.3 years, and the two tidal periods. At the solar period of 10.33, the two difference tones (7.74 and 23.22) are separated by precisely a factor of 3.