The imprint of the ENSO activities on the South China Sea wave climate

Global warming is changing the global wave climate, making waves stronger. In this study, we find that the wave climate in the South China Sea (SCS) undergoes an intensifying trend under global warming background, by examining the ERA-5 wave reanalysis data over 1979–2018. Results show a significant increase in most of the SCS, of 0.2% per year in significant wave height (SWH) and 0.15% per year in wave period (WP), but there is no significant change in surface wind speed (WS), which may correspond to the weakening of the Asian monsoon. The increase of the swell is the main characteristic of wave climate change in the SCS. We further examined the possible factors to cause the increasing of SWH, and found that the frequency of gale events occurring in the SCS and its adjacent regions increased over study period. The more frequent gale events can explain the significant increasing tendency of the SWH in the SCS by causing the occurrence of swell. The increasing appearance of gale events is closely related to the intensification of El Niño/Southern Oscillation (ENSO). ENSO activities also can regulate the interannual variability of wave climate in the SCS through the surface wind. Therefore, ENSO activities play an important role in the change of wave climate in the SCS.