On the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation: Might they be related?

The nature of the Pacific Decadal Oscillation ( PDO) is investigated based upon analyses of sea surface temperature observations over the last century. The PDO is suggested to be comprised of a 20 year quasi-periodic oscillation and a lower frequency component with a characteristic timescale of 60 years. The 20 year quasi-periodic oscillation is clearly identified as a phase locked signal at the eastern boundary of the Pacific basin, which could be interpreted as the signature of an ocean basin mode. We demonstrate that the 60 year component of the PDO is strongly time-lag correlated with the Atlantic Multidecadal Oscillation (AMO). On this timescale the AMO is shown to lead the PDO by approximately 13 years or to lag the PDO by 17 years. This relation suggests that the AMO and the 60 year component of the PDO are signatures of the same oscillation cycle.