Modulation of El Nino-Southern Oscillation by Freshwater Flux
and Salinity Variability in the Tropical Pacific |
| |
Authors: | ZHANG Rong-Hu ZHENG Fei PEI Yuhu ZHENG Quanan and WANG Zhanggui |
| |
Institution: | Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland, USA |
| |
Abstract: | The El Nino-Southern Oscillation (ENSO) is modulated by many
factors; most previous studies have emphasized the roles of wind stress and
heat flux in the tropical Pacific. Freshwater flux (FWF) is another
environmental forcing to the ocean; its effect and the related ocean salinity
variability in the ENSO region have been of increased interest recently.
Currently, accurate quantifications of the FWF roles in the climate remain
challenging; the related observations and coupled ocean-atmosphere modeling
involve large elements of uncertainty. In this study, we utilized
satellite-based data to represent FWF-induced feedback in the tropical Pacific
climate system; we then incorporated these data into a hybrid coupled
ocean-atmosphere model (HCM) to quantify its effects on ENSO. A new mechanism
was revealed by which interannual FWF forcing modulates ENSO in a significant
way. As a direct forcing, FWF exerts a significant influence on the ocean
through sea surface salinity (SSS) and buoyancy flux (QB) in the
western-central tropical Pacific. The SSS perturbations directly induced by
ENSO-related interannual FWF variability affect the stability and mixing in the
upper ocean. At the same time, the ENSO-induced FWF has a compensating effect
on heat flux, acting to reduce interannual QB variability during ENSO
cycles. These FWF-induced processes in the ocean tend to modulate the vertical
mixing and entrainment in the upper ocean, enhancing cooling during La Nina
and enhancing warming during El Nino, respectively. The interannual FWF
forcing-induced positive feedback acts to enhance ENSO amplitude and lengthen
its time scales in the tropical Pacific coupled climate system. |
| |
Keywords: | freshwater flux (FWF) forcing and feedback sea surface salinity
(SSS) variability ENSO modulation coupled ocean-atmosphere models |
本文献已被 CNKI SpringerLink 等数据库收录! |
| 点击此处可从《大气科学进展》浏览原始摘要信息 |
| 点击此处可从《大气科学进展》下载免费的PDF全文 |
|