Regional difference of sea surface salinity variations in the western tropical pacific

Yating Ouyang,Qiwei Sun,Yuhong Zhang,Jianwei Chi,Yan Du

doi:10.1007/s10872-021-00598-2

Abstract

Regional difference of sea surface salinity (SSS) variations in the western tropical Pacific is investigated with Ocean Reanalysis System 5 datasets. Three robust zonal bands of SSS variations have been identified in the northwestern tropical Pacific (NWTP), the western equatorial tropical Pacific (WEqP), and the southwestern tropical Pacific (SWTP), respectively. SSS in the WEqP and the SWTP has a strong interannual variability that is related to ENSO. In the WEqP, SSS variations are mainly controlled by anomalous freshwater flux, while in the SWTP they are governed by both freshwater forcing and oceanic processes. In the NWTP, SSS variations present a low-frequency variability that is correlated with Interdecadal Pacific Oscillation (IPO), which is mostly dominated by the freshwater flux and strongly adjusted by the ocean advection and mixed layer changes. After removing interannual signals, the SSS in all three regions are highly related to IPO, indicating that IPO has a general influence on the western tropical Pacific.

Highlights

Sea surface salinity (SSS) is a primary indicator of the hydrological cycle and air-sea interaction (Durack and Wijffels 2010; Hasegawa et al 2013)
The EOF1s of SSS in the western equatorial tropical Pacific (WEqP) and the southwestern tropical Pacific (SWTP) show a pair of dipole-like structure, which is negative in the equator and positive in the south during the positive phase of El Niño—Southern Oscillation (ENSO)
Prominent interannual variability of SSS is found in the WEqP and the SWTP and interdecadal variability of SSS in the northwestern tropical Pacific (NWTP)

Summary

Introduction

Sea surface salinity (SSS) is a primary indicator of the hydrological cycle and air-sea interaction (Durack and Wijffels 2010; Hasegawa et al 2013). Interannual variabilities in SSS are mainly driven by freshwater forcing that related to El Niño—Southern Oscillation (ENSO) associated processes in the western Pacific fresh pool, equatorial Pacific cold tongue, the Intertropical Convergence Zone (ITCZ), and the South Pacific convergence zone (Delcroix and Hénin 1991; Delcroix et al 1996; Maes 2000; Zhao et al 2016; Zheng and Zhang 2012). The SSS tendencies occurred in the past few decades suggest that there is a significant interdecadal variability overlapping on the monotonic freshening trend associated with global warming. Low-frequency oscillations like PDO and IPO can influence upper ocean salinity by changing the rainfall pattern in the tropical Pacific and the tropical-subtropical water transport in the Pacific circulation system (Du et al 2015, 2019; Li et al 2019; Zhang and Qu 2014)

Methods

Results

Conclusion