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

Monotonic decrease of the zonal SST gradient of the equatorial Pacific as a function of CO2 concentration in CCSM3 and CCSM4

“…The changes of ocean vertical thermal structure are also not uniform, a minimum warming occurs around the thermocline at depths of about 80–180 m in the western Pacific; i.e., the warming at the sea surface and in the region below the thermocline is greater than that around the thermocline (Figures e and f). This phenomenon is very common among climate models as greenhouse gas forcing is increased; the simulations of Vecchi and Soden [], Dinezio et al [], Burls and Fedorov [], and Luo et al [] with different climate models show the same phenomenon; and it could be a result of the shoaling of the thermocline, which brings deeper and colder waters upward [ Vecchi and Soden , ; Dinezio et al , ]. Moreover, the vertical temperature gradient (i.e., thermal stratification) increases in the wind‐mixed upper ocean and decreases below the thermocline (Figures g and h).…”

“…The strength of the zonal SST gradient influences the behavior of the El Niño–Southern Oscillation (ENSO), and surface temperature and precipitation in remote regions through the action of atmospheric teleconnections [ Alexander et al , ; Chiang , ]. Much effort has been expended in the exploration of the change of the zonal SST gradient with increased levels of anthropogenic greenhouse gases [ Collins and CMIP Modeling Groups , , ; Liu et al , ; Meehl et al , ; Vecchi et al , ; Dinezio et al , ; Xie et al , ; Yeh et al , ; An et al , ; Song and Zhang , ; Luo et al , ; Li et al , ]. The trend of this gradient in observations over the instrumental record, however, has remained unclear, perhaps due to the poor spatial and temporal sampling of SSTs [e.g., Tung and Zhou , ; Deser et al , ].…”

The positive Indian Ocean Dipole–like response in the tropical Indian Ocean to global warming

“…In addition, an overriding technique is employed as a diagnostic tool to isolate and evaluate the role of wind changes in the robust features of the tropical Indian Ocean. The overriding technique enables an isolation of individual feedbacks (e.g., the wind-thermocline-SST feedback) from other factors (Lu and Zhao, 2012;Luo et al, 2014).…”

“…For its counterpart in the Pacific where GW induces an El Niño-like condition, it was found that the physical mechanisms that drive tropical Pacific climate change depart substantially from the ENSO analogy that is often invoked for interpreting future 477 climate change (e.g., DiNezio et al, 2010); while being a major player in the positive feedback loop during El Niño, the weakening of the equatorial easterlies contribute only marginally to the El Niño-like SST pattern formation under GW (Luo et al, 2014). In addition, our recent model experiments also revealed distinct mechanisms for the El Niño-like Pacific warming under greenhouse gas forcing from El Niño (Luo et al, 2014).…”

Decomposition of thermal and dynamic changes in the South China Sea induced by boundary forcing and surface fluxes during 1970-2000

“…The sensitivity experiments in this study are based on the concept of a partial-coupling (P-C) method used widely in global fully coupled GCMs [Wu et al, 2003;Zhong et al, 2008;Lu and Zhao, 2012;Luo et al, 2014;Ding et al, 2014]; however, its applications in regional models has not been reported. In P-C experiments, one of atmospheric or oceanic variables is controlled in the coupled model, which allows for a partial airsea coupling, and therefore the effect of the controlled variable can be determined by the difference between the fully coupled experiment (control run) and the P-C experiments.…”