Spatial Variation in Rate of Temperature Change in South China Sea and Adjacent Northwest Pacific Ocean

Abstract

Abstract. Using the joint area of Asia, the Indian Ocean, and the western Pacific Ocean dataset, two transects were selected at 12 °N and 19 °N across the South China Sea (SCS) and adjacent northwest Pacific. The analysis covered the period from January 1993 to December 2006, investigating the spatial variation in the rate of change of sea temperatures. Results show that for the 12 °N transect of the southern SCS and northwest Pacific Ocean, the rate of temperature change in shallow (<200 m) waters is positive, with depth rate showed first increases and then decreases. Below 200 m, this trend reverses, with negative rates of temperature change for 200-1100-m layers. A positive rate of change is found for 1200-3000-m depths, but the warming rate is low. In the northwest Pacific Ocean, the rate of temperature change for 200-3000-m layers is negative, the cooling rate showed first increases and then decreases, and the maximum cooling rate is found at the 127 °E site in the 1100-m layer. In the northern SCS, the rate of 100-m shallow-sea temperature change is positive, with a reduced trend after the first increase in depth. For 100-900-m depths, the rate of temperature change is negative and the cooling rate after the first increase gradually decreases, with the maximum cooling rate found at the 116 °E site in the 200-m layer. For 900-2000-m depths, the rate of temperature change is positive, but the warming rate is small. For 2000-3000-m depths, the rate of change is negative and the cooling rate is very low. At 19 °N in the northwest Pacific, the rate of 300-m shallow-sea temperature change is positive, with a reduced trend after the first increase in depth. For 300-3000-m depths, the rate of change is negative, with small variations in the cooling rate. The maximum cooling rate is found at the 123 °E site in the 900-m layer. The temperature variation in the SCS is more complex than that in the northwest Pacific Ocean, and the greatest cooling rate is found in the southern SCS. The maximum rates of both warming and cooling were found at depths and not on water surfaces. Based on sea temperature variability, the SCS can be divided into more number of layers than the northwest Pacific Ocean. The southern SCS (at 12 °N) is divided into three layers and northern SCS (at 19 °N) is divided into four layers; on the other hand, the northwest Pacific Ocean is divided into two layers at both latitudes. And presumably stratified condition may be associated with currents.