Spring upper warm water of the Nansha Islands sea area in the South China Sea and the numerical study on its dynamic mechanism

Abstract

According to the satellite remote sensing monthly mean sea surface temperature data and in situ observational Conductivity-Temperature-Depth data, it is shown that in spring, at the upper layer to the west of Palawan Island, there exists a relatively weak warm water tongue which is distinctly different from the cold water southeast of the Balabac Strait. The relative temperature difference between the warm and cold water reduces gradually from winter to spring. P-vector method is employed to calculate the current field based on the in situ observational data, which shows that the warm water is within an anticyclonic meander. Based on the remote sensing wind stress during the observational period, a coupled single-layer/two-layer model is employed to study the dynamic mechanism of this anticyclonic meander current field corresponding to the warm water tongue. According to the numerical results, it is suggested that this anticyclonic meander could be mainly the residue of the winter anticyclonic eddy, rather than formed by the inflow water from the Sulu Sea via the Balabac Strait.