The pacific decadal precession and its relationship to tropical pacific decadal variability in CMIP6 models

Matthew H Rogers,Bruce T Anderson,Jason C Furtado

doi:10.1007/s00382-021-06114-y

Abstract

Persistent, multi-year shifts in atmospheric circulations and their associated influence on regional climates have profound impacts on physical, biological, and socioeconomic systems. The Pacific Decadal Precession (PDP), an atmospheric mode of variability consisting of a lower tropospheric height dipole which rotates counterclockwise over several years in the North Pacific, describes a series of such shifts in atmospheric circulations. One phase of the PDP, the north-south (N-S) phase, is hypothesized to be partially driven by central tropical Pacific (CP) sea surface temperature (SST) variability, but robust assessment of this dynamical connection in climate models remains to be done. In this study, we investigate this hypothesis with analyses in both reanalysis and selected models from the Coupled Model Intercomparison Project Phase 6 (CMIP6) archive. We show that the emergence of the N-S phase is both related to and influenced by tropical Pacific decadal SST variability, specifically variability associated with CP El Niño-Southern Oscillation (ENSO) events. When examining the pre-industrial runs of the CMIP6 models, we find that most models cannot recover the characteristic cyclonic precession of the dipoles of the PDP, instead featuring only amplitude and sign changes of the N-S phase, Moreover, the models do not replicate the dynamical connections between the tropical Pacific and this North Pacific mode of climate variability. Our results suggest that primary reasons for this inconsistency are that models inaccurately simulate both the SST pattern associated with the PDP, shared low-frequency power associated with CP ENSO events, and incorrect Rossby wavetrains emanating from the tropical Pacific into the North Pacific on quasi-decadal timescales. Taken together, our analyses offer another benchmark by which to test the fidelity of the climate model simulations in capturing Pacific decadal climate variability in order to improve decadal-to-centennial climate projections.

Highlights

Large-scale climate variations, like the North Pacific Gyre Oscillation (NPGO) (Di Lorenzo et al, 2008), the North Pacific Oscillation (NPO) (Rogers, 1981), and the Pacific Decadal Oscillation (PDO) (Mantua et al, 1997), have been linked to significant regional climate shifts in the North Pacific
This study demonstrated a relationship between the N-S phase of the Pacific Decadal Precession (PDP) and tropical Pacific climate variability
The SST anomalies (SSTa) pattern associated with the emergence of the N-S and phase of the PDP is similar the structure of CP El Nino-Southern Oscillation (ENSO) in HadISST, with statistically significant anomalies situated in the central Pacific (Fig. 4.1)

Summary

Introduction

Large-scale climate variations, like the North Pacific Gyre Oscillation (NPGO) (Di Lorenzo et al, 2008), the North Pacific Oscillation (NPO) (Rogers, 1981), and the Pacific Decadal Oscillation (PDO) (Mantua et al, 1997), have been linked to significant regional climate shifts in the North Pacific Examples of such shifts include persistent drought in California (Diffenbaugh et al, 2015), anomalously warm sea surface temperatures (SSTs) in the Gulf of Alaska (Bond et al, 2015; Di Lorenzo and Mantua, 2016), and the disruption of marine ecosystems in the Pacific (Mantua et al, 1997; Di Lorenzo et al, 2008). As a result of ENSO, the AL, and the PDO having such large impacts on Pacific climate, accurate seasonal to quasi-decadal predictions of climate variability for the North Pacific and North America are contingent upon understanding and predicting these modes

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