Abstract:

To understand the change rules of the upper ocean thermal state in the South China Sea (SCS), the vertical mean sea temperature of 5-366 m was characterized by the thermal content (HC) of the upper ocean in the South China Sea, the horizontal and vertical distribution characteristics and seasonal and interannual variability of upper thermal state in the South China Sea was analyzed based on the monthly subsurface sea temperature data of GODAS from 1980 to 2015. The results showed that: the horizontal distribution of annual mean HC in the SCS was characterized by high in east and low in west, the vertical zonal mean distribution was characterized by warm pool thickness and thermocline depth was thick (deep) in east and thin (shallow) in west; the vertical meridional mean performance was that the warm pool thickness was thick in the south and thin in the north, and the depth of the thermocline was shallower in the middle and deep on both sides; the biggest change of the sea temperature was kept in the subsurface (75-200 m) over the SCS, and the anomaly of the temperature in different depths had obvious interannual and interdecadal variability; the average HC in the SCS region was the highest in autumn, followed by that in spring and summer, and the lowest was in winter and the interannual variability of HC was obvious, and there was a significant mutation after 1998, which changed from negative to positive, showing an obviously warming trend; the spatial distribution of the first mode of S-EOF in the HC revealed high in east and low in west, the corresponding time series had interdecadal transitions in the late 1990s, which were mainly negative values transformed into positive values, in terms of spatial distribution, the HC was transformed from the west high and east low type to the east high and west low type.

Key words: thermal state, horizontal distribution, vertical distribution, seasonal change, interannual change, the South China Sea