Changes In Surface Salinity In The South China Sea And The Adjacent Pacific Ocean From 1871 To 2010

Climate change has become the most important environmental issue in today’s society,and strengthening the global response to the threat of climate change has become the consensus of the international community.The ocean is an important regulator of climate,especially in tropical seas.It is a heat source and an "engine" for the climate system that transports energy to high latitudes.It plays a key role in the global climate system.Revealing the distribution characteristics,change process and influencing mechanism of salinity of marine hydro-climate and environmental elements is the main way to understand climate change from the ocean.In this paper,using the simplified global ocean data assimilation system analysis after reanalysis product SODA-2.2.4 month average data,using the moving average method,sliding T test,linear least squares fitting method and wavelet analysis,explore the climate of the south China sea and adjacent Pacific base period 1981-2010 surface salinity distribution characteristics and in 1871-2010 surface salinity changes and cycle characteristics.In this way,we can study the important issues of climate change in today’s society and provide the basis of ocean data for climate prediction.The following conclusions are drawn:1)From 1981 to 2010,the average climatic state of surface salinity in the study area was: the surface salinity of the south China sea generally showed a trend of decreasing from northeast to southwest;The surface salinity of the western Pacific Ocean generally shows a trend of decreasing from the south and north sides to the waters around 8°N.According to the average monthly distribution of surface salinity in the study area,it was found that the distribution pattern of surface salinity in the south China sea decreased from northeast to southwest from October to may of the next year.From June to September,the distribution pattern decreases from the central12.25-18.25°N sea to the south and north.From January to December,the surface salinity of the western Pacific Ocean always presents a high-low-second-highdistribution pattern from north to south.2)According to the climatic distribution and intermonthly variation characteristics of surface salinity in the study area from 1981 to 2010,the study is divided into eight zones:The northern sea area of the South China Sea,the waters near the Mekong River,the western sea in the south China Sea(except the waters near the Mekong River),the eastern sea in the south China Sea,the northern high-salt area of the Northwest Pacific Ocean,the central low-salt area of the Northwest Pacific Ocean,the secondary high-salt area of the south Northwest Pacific Ocean,the Sulu Sea and the Sulawesi Sea.3)From 1871 to 2010,the general trend of surface salinity change in the study area was an increasing trend with a variation rate of 0.0023psu/a.In the 140 years,the linear trend of surface salinity from January to December in each month was also on the rise,but the rise rate and fluctuation range were the smallest in February and the largest in August.However,the variation rate of 140-year linear fitting varies greatly in space.In the south China sea,roughly 17.25°N and 117.25°E are the boundaries.The waters north and east of the boundary mainly show an upward trend,especially in the south of the Taiwan strait.The sea area to the west of the boundary mainly shows a downward trend.In the past 140 years,the surface salinity of the western Pacific Ocean has been on the rise.4)According to the variation characteristics of surface salinity in the internal characteristic points of the South China Sea in 140 years,it is found that the surface salinity of the whole South China Sea changed greatly from 1950 to 1970,and from1900 to 1940,the surface salinity of the south China Sea changed greatly again.5)The surface salinity in the study area has the characteristics of multi-scale time variation,and has the characteristics of large scale and small scale.Among them,the time scale of 51 a is the first main period,and the time region is the strongest,with an average period of about 33 a.The surface salinity of the south China sea mainly follows the time scale of 35-65 a,especially from 1930 to 1980.Under this scale,the average period of high and low oscillation is about 32-34 a.The internal periodic features of the Western Pacific are relatively complicated.The salinity in the northern high-salin region and the Luzon Strait mainly follows the mid-time scale high-low oscillation period,and the average periods are about 19-24 a.The central low-salt area,the Sulu Sea,and the Sulawesi Sea mainly follow large-scale high-low oscillation cycles,with an average period of about 37-40a;the southern high-salt area has anaverage period of about 12 a.