Understanding the El Nino-like oceanic response in the tropical Pacific to global warming

TitleUnderstanding the El Nino-like oceanic response in the tropical Pacific to global warming
Publication TypeJournal Article
Year of Publication2015
AuthorsLuo Y.Y, Lu J., Liu F.K, Liu W
JournalClimate Dynamics
Volume45
Pagination1945-1964
Date Published2015/10
Type of ArticleArticle
ISBN Number0930-7575
Accession NumberWOS:000362667100016
KeywordsAtmospheric circulation; climate; coupled ocean; El Nino-like response; enso; equatorial pacific; future climate; global warming; model; multimodel; Nino; Oceanic dynamical; response; temperature-change; thermocline; thermostat
Abstract

The enhanced central and eastern Pacific SST warming and the associated ocean processes under global warming are investigated using the ocean component of the Community Earth System Model (CESM), Parallel Ocean Program version 2 (POP2). The tropical SST warming pattern in the coupled CESM can be faithfully reproduced by the POP2 forced with surface fluxes computed using the aerodynamic bulk formula. By prescribing the wind stress and/or wind speed through the bulk formula, the effects of wind stress change and/or the wind-evaporation-SST (WES) feedback are isolated and their linearity is evaluated in this ocean-alone setting. Result shows that, although the weakening of the equatorial easterlies contributes positively to the El Nio-like SST warming, 80 % of which can be simulated by the POP2 without considering the effects of wind change in both mechanical and thermodynamic fluxes. This result points to the importance of the air-sea thermal interaction and the relative feebleness of the ocean dynamical process in the El Nio-like equatorial Pacific SST response to global warming. On the other hand, the wind stress change is found to play a dominant role in the oceanic response in the tropical Pacific, accounting for most of the changes in the equatorial ocean current system and thermal structures, including the weakening of the surface westward currents, the enhancement of the near-surface stratification and the shoaling of the equatorial thermocline. Interestingly, greenhouse gas warming in the absence of wind stress change and WES feedback also contributes substantially to the changes at the subsurface equatorial Pacific. Further, this warming impact can be largely replicated by an idealized ocean experiment forced by a uniform surface heat flux, whereby, arguably, a purest form of oceanic dynamical thermostat is revealed.

DOI10.1007/s00382-014-2448-2
Short TitleClim. Dyn.
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