A Preliminary Study On The Interannual-to-Interdecadal Variability Of Thermohaline Structures In The Northern East China Sea

Recent studies showed that notable climatological variability, especially interannual-to-interdecadal variability exists in the atmosphere and the ocean. It is important to study the climatological variability in the East China Sea (ECS), which is yet a pitiful blank. In this paper, data gathered during 1957-1996 were used to study the climatological variability in the northern ECS, through statistical methods such as EOF decomposition, correlation analysis, and maximum entropy spectrum analysis. The conclusions were drawn as follows:1. Distributions of multiyear mean temperature and salinity in summer indicated that the mean increase of SST in the studied area from 1957-1976 to 1977-1996 was 0.457oC with large amplitude distributing mainly south of 31oN, and the Taiwan Warm Current got stronger. Results of the EOF and correlation analyses showed that the climatological shifts were primarily influenced by the variability of the Kuroshio with period longer than 40 years.2. Distributions of multiyear mean temaperature and salinity in winter indicated that the mean increase of SST in the studied area from 1957-1976 to 1977-1996 was 0.244oC . Temperature adjacent to the Changjiang River Estuary decreased dramatically with the extreme of -4.4oC, while mean SST increase in the other part of the studied area was 0.529oC after 1976. As the results suggested, the climatological shift was primarily induced by variability of the air temperature and the decrease of temperature adjacent to the Changjiang River Estuary was influenced by the run-off of the Changjiang River. 3. Main control factors of the thermohaline structures in the northern ECS and their climatological variability were concluded as follows:a) Atmospheric forcing is one of the main influence factors of the variability of temperature on interdecadal time scale in summer and winter. Especially, it's variations were the primary reason of the climatological shift of SST in winter;b) Kuroshio is one of the main influence factors of the variability of temperature on decadal and interdecadal time scale in summer and winter. Variations of the Kuroshio's transport was the primary reason of the climatological shift of SST and temperature/salinity at 20 m depth in summer;c) The Changjiang River run-off is the main infuence factor of SSS adjacent to the Changjiang River Estuary with effecting area (west of 125oE) in summer larger than that in winter (west of 123.5oE).4. Distribution of standard deviation of SSS in summer showed that, the Changjiang River Diluted Water had two extending paths: one to the northeast while the other to the southeast till reaching 123oE.