Characteristics of the transition Layer in the South China Sea in 1998

CTD data on standard levels collected during July and December in 1998 and the cu-bic spline interpolating method were used to study the characteristics of the transition layer tempera-ture and salinity. The thermocline undergoes remarkable seasonal variation in the South China Sea(SCS), and especially in the region of the north shelf where the thermocline disappears in Decem-ber. The thermocline is stronger and thicker in July than in December. There is no obvious seasonalvariation in the halocline. Due to the upper Ekman transport caused by monsoon over the SCS, thethermocline slopes upward in July and downward in December from east to west in the northernSCS. The characteristics of the thermocline and halocline are influenced by local eddies in theSCS. The Zhujiang diluted flow influences significantly the SCS shelf's halocline.