A study of response of thermocline in the South China Sea to ENSO events

Abstract

This paper investigates the response of the thermocline depth (TD) in the South China Sea (SCS) to the El Nino-Southern Oscillation (ENSO) events using 51-year (from 1960 to 2010) monthly seawater temperature and surface wind stress data acquired from the Simple Ocean Data Assimilation (SODA), together with heat flux data from the National Centers for Environmental Prediction (NCEP), precipitation data from the National Oceanic and Atmospheric Administration (NOAA) and evaporation data from the Woods Hole Oceanographic Institution (WHOI). It is indicated that the response of the SCS TD to the El Nino or La Nina events is in opposite phase. On one hand, the spatial-averaged TDs in the SCS (deeper than 200 m) appear as negative and positive anomalies during the mature phase of the El Nino and La Nina events, respectively. On the other hand, from June of the El Nino year to the subsequent April, the spatial patterns of TD in the north and south of 12°N appear as negative and positive anomalies, respectively, but present positive and negative anomalies for the La Nina case. However, positive and negative TD anomalies occur almost in the entire SCS in May of the subsequent year of the El Nino and La Nina events, respectively. It is suggested that the response of the TD in the SCS to the ENSO events is mainly caused by the sea surface buoyancy flux and the wind stress curl.