Variability in upper-ocean salinity stratification in the tropical Pacific Ocean |
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| Authors: | Wei Duan Xuhua Cheng Xiuhua Zhu Tian Ma |
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| Institution: | 1.College of Oceanography, Hohai University, Nanjing 210098, China2.Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519000, China3.Center for Earth System and Sustainability, University of Hamburg, Hamburg 20144, Germany |
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| Abstract: | Using a gridded array for real-time geostrophic oceanography(Argo) program float dataset, the features of upperocean salinity stratification in the tropical Pacific Ocean are studied. The salinity component of the squared Brunt-V?is?l? frequency N~2( N_S~2) is used to represent salinity stratification. Layer-max N_S~2(LMN), defined as the N_S~2 maximum over the upper 300 m depth, and halocline depth(HD), defined as the depth where the N_S~2 maximum is located, are used to specifically describe the intensity of salinity stratification. Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability. Over the western and eastern equatorial Pacific, the LMN has a large magnitude with a shallow HD, and both have completely opposite distributions outside of the equatorial region. An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations, followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline, significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event. When an El Ni?o event occurs, the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward, together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool. The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves. |
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| Keywords: | Brunt-V?is?l? frequency salinity stratification seasonal and interannual variations gravity wave |
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