Summer surface warming driven by the strong El Niño in the South China Sea

The interannual variability of sea surface temperature (SST) in the South China Sea (SCS) exhibits two warming peaks around January and August in the subsequent year of El Nino. Results show that the second basin-scale SST warming peak is only evident following strong El Nino events, not regular events, which can be well identified by the Empirical Orthogonal Function (EOF) method. The heat budget analysis reveals that the anomalous Ekman heat advection (Eka) and geostrophic heat advection (Goa) contribute to the second warming feature, associated with the local dynamic response in the SCS, such as wind-driven Ekman downwelling, weakened Vietnam coastal upwelling, and abnormal anticyclonic geostrophic currents. The abnormal Eka and Goa are further attributed to the advanced abnormal equatorial easterlies breakout in the western Pacific, coinciding with the development of the western North Pacific anomalous anticyclone (WNPAC) in response to strong El Nino. This suggests that the second warming feature of the SCS SST is the footprint of strong El Nino events via the establishment of the WNPAC, which is tightly related to Indo-Pacific remote processes.