Asymmetry of Salinity Variability in the Tropical Pacific during Interdecadal Pacific Oscillation Phases

• Published in: Advances in atmospheric sciences Vol. 40; no. 7; pp. 1269 - 1284
• Main Authors: Zhi, Hai, Yang, Zihui, Zhang, Rong-Hua, Lin, Pengfei, Qi, Jifeng, Huang, Yu, Dong, Meng
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.07.2023; Springer Nature B.V; Laoshan Laboratory,Qingdao 266237,China%State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG),Institute of Atmospheric Physics(IAP),Chinese Academy of Sciences,Beijing 100029,China%Laoshan Laboratory,Qingdao 266237,China; College of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China%School of Marine Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China; Key Laboratory of Ocean Circulation and Waves,Institute of Oceanology,and Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China
• Subjects: Amplitude; Amplitudes; Asymmetry; Atmospheric Sciences; Budgets; Chemical analysis; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; Equator; Evaporation; Freshwater; Geophysics/Geodesy; Inland water environment; La Nina; Meteorology; Original Paper; Phases; Salinity; Salinity effects; Sea surface; Seawater; Seawater density; Southern Oscillation; Stratification; Surface salinity; Variability; Water analysis; 盐度变化不对性; 上层海洋层结; tropical Pacific; 热带太平洋; Interdecadal Pacfic Oscillation; 太平洋年代涛动; salinity variability asymmetry; upper-ocean stratification
• ISSN: 0256-1530; 1861-9533
• DOI: 10.1007/s00376-022-2284-y

It has been recognized that salinity variability in the tropical Pacific is closely related to the Interdecadal Pacific Oscillation (IPO). Here, we use model simulations from 1900 to 2017 to illustrate obvious asymmetries of salinity variability in the tropical Pacific during positive and negative IPO phases. The amplitude of salinity variability in the tropical Pacific during positive IPO phases is larger than that during negative IPO phases, with a more westward shift of a large Sea Surface Salinity (SSS) anomaly along the equator. Salinity budget analyses show that the asymmetry of salinity variability during positive and negative IPO phases is dominated by the difference in the surface forcing associated with the freshwater flux [FWF, precipitation (P) minus evaporation (E)], with a contribution of 40%–50% near the dateline on the equator. Moreover, the relationships between the salinity variability and its budget terms also show differences in their lead-lag correlations during positive and negative IPO phases. These differences in salinity variability during different IPO phases produce asymmetric effects on seawater density which can reduce or enhance upper-ocean stratification. Therefore, the salinity effects may modulate the intensity of El Niño-Southern Oscillation (ENSO), resulting in an enhanced (reduced) El Niño but a reduced (enhanced) La Niña during positive (negative) IPO phases by 1.6°C psu −1 (1.3°C psu −1 ), respectively. It is suggested that the asymmetry of salinity variability may be related to the recent change in ENSO amplitude associated with the IPO, which can help elucidate ENSO diversity.