Atlantic–Pacific Links in Observed Multidecadal SST Variability: Is the Atlantic Multidecadal Oscillation’s Phase Reversal Orchestrated by the Pacific Decadal Oscillation?

Abstract

The Atlantic and Pacific basin are found linked in the context of multidecadal SST variability from analyses of 118 years of observational data. Recurrent spatiotemporal variability, including multidecadal modes, was identified using the extended-EOF technique in a longitudinally global domain, allowing unfettered expression of interbasin interactions. The physicality of the obtained decadal modes was assessed using fishery records and analog counts. A three-mode structure with bi-directional interbasin links frames the new perspective on the cycling of multidecadal SST variability. The three modes are the Atlantic multidecadal oscillation (AMO), low-frequency North Atlantic Oscillation (LF-NAO), and North Pacific decadal variability [PDV-NP; resembling negative (–ve) PDO]. The two previously documented links AMO→PDV-NP (with ~12.5-yr lead) and LF-NAO→AMO (with 16-yr lead) are corroborated, while a third one, PDV-NP→(−LF-NAO) with ~6.5-yr lead, is uncovered. The interaction triad closes the loop on the cycling of multidecadal SST variability, generating AMO’s phase reversal in ~35 years, consistent with its widely noted ~70-yr time scale. The two previously noted links—one intrabasin and one interbasin—were unsuccessful in this regard. Other findings include the deeper subsurface extensions of Atlantic multidecadal SST variability, and the hitherto unrecognized similarity of Pan-Pacific decadal variability and North Pacific Gyre Oscillation. Instrumental records, albeit short in the context of multidecadal variability, must continue to be mined for insights into the functioning of the climate system as its model representations while improving, remain inadequate.

Emerging Pacific Quasi‐Decadal Oscillation Over the Past 70 Years

“…The QDO, the prominent mode of the SST variability in the equatorial central Pacific, involves a sequence of air‐sea interaction in the subtropical North Pacific. Therefore, QDO's off‐equatorial SST patterns in the developing stage (−3, −1, and 0 years) resemble those of two leading modes of the North Pacific decadal variability, i.e., NPGO (Di Lorenzo et al., 2008) and the Pan‐Pacific Decadal variation mode or PDO (Nigam et al., 2020). However, the QDO also involves the equatorial coupled dynamics on the decadal time scale.…”

North Atlantic as a Trigger for Pacific‐Wide Decadal Climate Change

“…Coupled model results also argue that the observed AMV influences the North Pacific decadal SST variability via the Northern Hemisphere storm tracks and positive ocean‐air feedbacks over the North Pacific (Zhang & Delworth, 2007). Statistical results of 118‐year observations demonstrate that there exists an Atlantic‐Pacific connection at low‐frequency timescales (Nigam et al., 2020). Although the tropical (Meehl et al., 2020) and extratropical pathways have been proposed to explain the cross‐basin Atlantic‐Pacific teleconnection, there is still no agreement on the underlying mechanism of how the AMV drives the IPO on decadal timescales without anthropogenic warming signals.…”

Impacts of Atlantic Multidecadal Variability on the Tropical Pacific: a multi-model study

“…Finally, we note that several observational and model-based studies [49][50][51] suggest the existence of a two-way interaction between Atlantic and Pacific at decadal timescale: an AMV warming driving a Pacific cooling, which eventually drives an Atlantic cooling. Due to the experimental protocol used in the present article, we could only focus on the representation by models of the Atlantic impacts on the Pacific.…”