A coral δ18O record of ENSO driven sea surface salinity variability in Fiji (south -western tropical Pacific)

AbstractRegional 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.

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Sea Surface Salinity Change since 1950: Internal Variability Versus Anthropogenic Forcing

Journal of Climate ◽

10.1175/jcli-d-20-0331.1 ◽

2020 ◽

pp. 1-46 ◽

Cited By ~ 2

Author(s):

Qiwei SUN ◽

Yan DU ◽

Shang-Ping XIE ◽

Yuhong ZHANG ◽

Minyang WANG ◽

...

Keyword(s):

Indian Ocean ◽

Internal Variability ◽

Tropical Pacific ◽

Sea Surface ◽

Sea Surface Salinity ◽

Surface Salinity ◽

Term Trend ◽

Western Tropical Pacific ◽

Long Term Trend

AbstractUsing an eastern tropical Pacific pacemaker experiment called the Pacific Ocean–Global Atmosphere (POGA) run, this study investigated the internal variability in sea surface salinity (SSS) and its impacts on the assessment of long-term trends. By constraining the eastern tropical Pacific sea surface temperature variability with observations, the POGA experiment successfully simulated the observed variability of SSS. The long-term trend in POGA SSS shows a general pattern of salty regions becoming saltier (e.g., the northern Atlantic) and fresh regions becoming fresher, which agrees with previous studies. The 1950-2012 long-term trend in SSS is modulated by the internal variability associated with the Interdecadal Pacific Oscillation (IPO). Due to this variability, there are some regional discrepancies in the SSS 1950–2012 long-term change between POGA and the free-running simulation forced with historical radiative forcing, especially for the western tropical Pacific and southeastern Indian Ocean. Our analysis shows that the tropical Pacific cooling and intensified Walker Circulation caused the SSS to increase in the western tropical Pacific and decrease in the southeastern Indian Ocean during the 20-year period of 1993–2012. This decadal variability has led to large uncertainties in the estimation of radiative-forced trends on a regional scale. For the 63-year period of 1950–2012, the IPO caused an offset of ∼40% in the radiative-forced SSS trend in the western tropical Pacific and ∼170% enhancement in the trend in the southeastern Indian Ocean. Understanding and quantifying the contribution of internal variability to SSS trends help improve the skill for estimates and prediction of salinity/water cycle changes.

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