Distinguishing the Quasi-Decadal and Multidecadal Sea Level and Climate Variations in the Pacific: Implications for the ENSO-Like Low-Frequency Variability

Jin-Yi Yu,Kewei Lyu,John A Church,Jianyu Hu,Xuebin Zhang

doi:10.1175/jcli-d-17-0004.1

Abstract

Low-frequency sea level variations with periods longer than interannual time scales have been receiving much attention recently, with the aim of distinguishing the anthropogenic regional sea level change signal from the natural fluctuations. Based on the available sea level products, this study finds that the dominant low-frequency sea level mode in the Pacific basin has both quasi-decadal variations and a multidecadal trend reversal in the early 1990s. The dominant sea level modes on these two time scales have different tropical structures: a west–east seesaw in the tropical Pacific on the multidecadal time scale and a dipole between the western and central tropical Pacific on the quasi-decadal time scale. These two sea level modes in the Pacific basin are closely related to the ENSO-like low-frequency climate variability on respective time scales but feature distinct surface wind forcing patterns and subbasin climate processes. The multidecadal sea level mode is associated with the Pacific decadal oscillation (PDO) and Aleutian low variations in the North Pacific and tropical Pacific sea surface temperature anomalies toward the eastern basin, while the quasi-decadal sea level mode is accompanied by tropical Pacific sea surface temperature anomalies centered in the central basin along with the North Pacific part, which resembles the North Pacific Oscillation (NPO) and its oceanic expressions [i.e., the North Pacific Gyre Oscillation (NPGO) and the Victoria mode]. The authors further conclude that the ENSO-like low-frequency variability, which has dominant influences on the Pacific sea level and climate, comprises at least two distinct modes with different spatial structures on quasi-decadal and multidecadal time scales, respectively.

Highlights

Global mean sea level has been rising with an increasing contribution from the anthropogenic forcing (e.g., Church and White 2011; Dangendorf et al 2015; Slangen et al 2016)
We found that the Pacific basin QD and MD sea level modes are closely related to the El Niño–Southern Oscillation (ENSO)-like low-frequency variability and exhibit different patterns for various climate variables on these two time scales
Our results indicate that the dominant mode of low-frequency sea level variations in the Pacific basin exhibits both QD cycles and an MD trend reversal around the early 1990s (Fig. 3a)

Summary

JULY 2017

Distinguishing the Quasi-Decadal and Multidecadal Sea Level and Climate Variations in the Pacific: Implications for the ENSO-Like Low-Frequency Variability. State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China, and Department of Earth System Science, University of California, Irvine, Irvine, California. Commonwealth Scientific and Industrial Research Organisation Oceans and Atmosphere, Hobart, Tasmania, Australia. Climate Change Research Centre, University of New South Wales, Sydney, New South Wales, Australia. State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen, China

Introduction

Data and methodology

Atmospheric forcing patterns and origins for QD and MD sea level modes

ENSO-like low-frequency variability

Summary and discussion