Cycles in oceanic teleconnections and global temperature change

Abstract

Three large ocean currents are represented by proxy time series: the North Atlantic Oscillation (NAO), the Southern Oscillation Index (SOI), and the Pacific Decadal Oscillation (PDO). We here show how proxies for the currents interact with each other and with the global temperature anomaly (GTA). Our results are obtained by a novel method, which identifies running average leading–lagging (LL) relations, between paired series. We find common cycle times for a paired series of 6–7 and 25–28 years and identify years when the LL relations switch. Switching occurs with 18.4 ± 14.3-year intervals for the short 6–7-year cycles and with 27 ± 15-year intervals for the 25–28-year cycles. During the period 1940–1950, the LL relations for the long cycles were circular (nomenclature x leads y: x → y): GTA → NAO → SOI → PDO → GTA. However, after 1960, the LL relations become more complex and there are indications that GTA leads to both NAO and PDO. The switching years are related to ocean current tie points and reversals reported in the literature.