| The East China Sea is the marginal sea of the western Pacific and one of the important areas affecting China's climate.Salinity is an essential element for characterizing ocean physics and chemistry,and is one of the characteristic indicators reflecting ocean hydrology and climate.On the edge of the continental shelf of the East China Sea,there is a strong current of high temperature and high salt all year round-the East China Sea Kuroshio.In addition,Taiwan's warm currents,the warm currents of the horses,the Yangtze River dilute water,and the north Jiangsu coastal currents,etc.,all of them have a profound impact on the salinity field of this sea area.It is necessary to study the structure,time and space changes of the marine hydrological and climatic environment in the region,and the relationship between them and the surrounding seas,in order to lay a foundation for further understanding of climate change in China,provide a basis for climate prediction,and effectively manage this land.This article uses the monthly average salinity data for the 140 years from 1871 to 2010 in the SODA-2.2.4 dataset and the global seabed topographic database published by the National Geophysical Data Center in 2009.Through the MATLAB computer platform,the salinity data of 1870-2010,the surface of the study sea area for 12 months and 140 years of total 1680 months were programmed and analyzed by means of sliding average method and empirical orthogonal analysis to analyze the East China Sea in 140 years.In the adjacent northwestern Pacific Ocean,the distribution characteristics of surface salinity climatic states yield the following results:1)The average salinity of the surface layer of the East China Sea and the adjacent northwestern Pacific Ocean 30 a gradually increases from northwest to southeast,forming three distinct salinity characteristics: the East China Sea continental shelf sea area,the East China Sea Kuroshio Sea area and the Northwest Pacific Ocean area.In the East China Sea continental shelf,the annual variation of salinity in three regions is 2-15 times the normal variation of the sea area;Among them,two are abnormally appearing near the river estuary;a negative anomaly is located at 122°E,29°N,which is the coast of Zhejiang in the south of Hangzhou Bay,which is closely related to the influence of the Yangtze River dilute water and the Taiwan warm curren.2)In the inter-monthly variation of surface salinity in the study area 30 a,the monthly salt lines are gradually sparsely from east to south with the Yangtze River estuary as the center.The northerly region of the Yangtze River estuary has the largest monthly variation of salinity.The smaller the monthly variation of salinity.The monthly variation of surface salinity has obvious periodicity;among them,the monthly variation of the maximum and average salinity is not obvious,and the monthly variation of the minimum value is significant,showing a tensile "S" curve,and the peak appears in In March,the valley appeared in August.3)By analyzing the selected 22 typical feature points,it can be seen that the variation of the Pearl River Estuary is significantly smaller than that of the Yangtze River estuary,which has a certain relationship with the difference in the size of the runoff between the two;The closer to the shelf,the lower the salinity and the greater the annual variation of salinity.On the contrary,the more offshore,the higher the salinity and the smaller the annual variation of salinity;In the summer,the waters around Hangzhou Bay were inhibited by the north Jiangsu coast and were affected by the warm current of Taiwan.The monthly variation of salinity showed the opposite characteristics of other sea areas in the study area: summer salinity was higher than winter.In the West Pacific Sea,except for special points,the salinity generally increases with the increase of longitude at the same latitude,but in the same longitude,the salinity does not increase or decrease with the increase of latitude;Unlike the monthly variation of salinity,the difference in salinity does not show a tendency to change with longitude at the same latitude.4)Five sections were selected in the study area to analyze the spatial variation of salinity.It can be seen that the salinity value is gradually increasing from west to east.The closer to the shelf,the higher the salinity,the closer to the Yangtze River estuary,the Yangtze River.The effect of dilute water,the greater the change in salinity.5)The 140-year study area salinity distribution is not much different from the new climate reference period: it is low in the northwest and high in the southeast.It is increasing from the continental shelf of the East China Sea to the northwestern Pacific Ocean,but it is 123°E and 21.25° in the western Pacific.N——131°E,30°N line eastward until 126°E,23°N-132°E sea area,the salinity value is between 34.25-34.5psu,and the sea area is 34.5psu in the new climate reference period.For the 140-year surface salinity annual amplitude of the study area,the annual salinity amplitudes of the East China Sea continental shelf and the East China Sea Kuroshio Sea area are the same as the annual amplitude distribution of the new climate reference period,while the annual amplitude of the Pacific Northwest in 140 years is higher than the new climate.Base period.6)In the 140 years,the surface salinity of the study area,the overall trend is rising,but in stages,in 1871-1882,1901-1954,1955-1965 is the rising stage of salinity,in 1883-1900,1966-2010 is the stage of salinity decline;Before 1900,the sea surface salinity anomaly was mainly represented by negative anomalies,and positive anomalies were mainly after 1900.The periodic variation characteristics of surface salinity in 140 years can be seen from the global wavelet power spectrum.The time period scale is relatively simple,there is only one time scale,and the main period is about 18 years.7)The six sections will be in the stage of salinity rise from 1871 to 1882,from 1883 to 1900 and from 1966 to 2010. |
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