Kuroshio Zone Salinity In Different Seasons Of The PN Section Interannual / Decadal Changes

The Kuroshi is the western boundary current of the North Pacific subtropicalcirculation，it is a strong oceans flow as famous as the Gulf Stresm in the North AtlanticOcean.Kuroshio in the East China Sea has the characteirstics of high temperature,highsalt，high velocity,large flow,is the main dirving force of China offshore circulationwairation，has an important inlfuence on the climate enviroment in china.Salinity is a basic element of characterization of physical oceanography andchemical characteirstics,is one of the characteirstics of index reflecting the marinehydrology and climate.Changes in ocean salinity is a good indicator of local and globalhydrological cycle.However,the relative scarcity of ocean salinity measurementdiiffculties and the relative lack of observation data,also the data distribution in time andspace is not continuous?all increasing the diiffculty of ocean salinity changes.The PN section is one of the most important cross-section for observation andstudy in the East China Sea and the Kuroshio.The section distirbution is from EastChina Sea north-west corner of the mouth of the Yangze River to the south-east cornerof the Ryukyu Islands,northwest to southeast direction;the longtitude and latitudecoordinates is west from30.5。N，124.5。E to east27.5。N，128.25。E，is a cutting spindle ofcross-section of the central part of the East China Sea and the Kuroshio for observationfor many years.Research shows that,oceanographic have signiifcant inter-annual variations anddecadal changes.Interannual vairation,such as ENSO and its influence; interdecadalvairation?the Pacific Decadal Oscillaiton in the Pacific for the first mode(POD).Around1976M977, in the North Paciifc decadal abrupt climate change and transformation,itsreason mainly to PDO.In this paper,with the reanalysis data rfom1945to2010in the East ChinaSea,extract the PN section in the summer(in August on behalfof)>winter(February),spirng(May)aiid autumn(November)0-700m salinity data,take theslice,feature point localization,feature extraction and other methods to explore the PNsection four seasons salinity structure interannual and decadal change process， long-term trends and the influencing factors.To lay the foundation for the furtherunderstanding of the impact of Kuroshio for the climate change of China,provide thebasis for climate prediction.Draw the following conclusions:(1)The inter annual vairability of Salinity Characteirstic values in the PN sectionin four seasons: there are a "W" type change of Each layer Salinity Characteirstic valuesof0-300meters in four seasons in1976/1977years ago, that has a peak and two valley.After1976/1977years，the salinity characteirstics values lfuctuated around the average.300-500’m and500-700m water layers dont have "the characteirstic change of W "，because the water source of these two layers is different from the water source of theupper levels.From1945-2010, the salinity characteristic values d’ont appeared significantchange, but since2001-2010years, the salinity characteirstic values have decreasingtrend in summer, minimum value decreased most signiifcantly. The maximum,minimum and average in winter, spring and autumn decrease in accordance. From thesurface layer to the bottom layer, the surface characteirstic value decreased mostobviously. The reduce the surface salinity characteirstic value may be affected by theglobal warming.(2)Thedecadal changes of Salinity Characteirstic values in PN section in fourseasons: It can be draw a conclusion that the point mutation of four seasons in0-300meters each layer was in1956，1976and between eighty years to ninety years bymutation test and mutation analysis of average value salinity of the four seasons0-700meters of each layer. The reason of the mutation point around1956has to be explainedlater. The reason of the point mutations in about1976is probably the cold and warmPDO phase transition. The reason of the mutations between eighty years to ninety yearsis probably decreasing salinity.The distirbution of the300-500,500-700m layer’s jump point is different rfomthe upper level’s, because the water source of300-700m layers is different from thewater source of0-300m layers.(3)Thehigh-salt nuclear intensity of PN section changes in seasons: the high-salt nuclear intensity in seasons and the maximum value of salinity in PN section has higherconsistency，by a99.9%confidence level. Similarly, high-salt nuclear intensity also noobvious trend in the the1945-2010entire time sequence, the intensity of2001-2010high salt nuclear in four seasons reduced0.0407,0.0345,0.0341and0.0534，the averageof high-salt nuclear intensity respectively were17.96%，24.7%,17,67%，19.1%. Theresult uesd by mutation analysis and mutation test to high salt nuclear intensity in fourseasons resemble the0-300meters layers salinity average, high-salt nuclear intensityand salinity characteirstic values of both common response to changes in the salinity ofthe PN section features. Both of high salt nuclear intensity and salinity characteirsticvalues were common responsed to the variation of the salinity of the PN section.(4)The space changes of the PN section salinity in four seasons: According to thejump point divided the entire time seires of the summer, autumn and winter into fourtime peirods, and divided the entire time series of spirng in1945-2010into three timeperiods. In1976years before and atfer, the mean change of the entire cross-section ofthe peirod of time unlike other peirods less signiifcant, this also explains the jump pointis not primairly due to the mean shitf caused about1976. Spatial vairation and mutationanalysis to conifrm each other.‘(5)Thesalinity cyclical changes of PN section in1945-2010four seasons: Thesalinity eigenvalues and high salt nuclear intensity exist2-4years, six-year,11-year,18-year Change cycle, Period of2-4years and6-year are likely to be inlfuenced by ElNino, and the period of11-year and18-year effected by the boundary，but this result hasyet to be confirmed.(6)Therelationship of PN section in1945-2010Four Seasons salinity change withENSO，PDO: Nino3.4District ENSO index ahead of PN sectional spirng, summer,autumn, winter0-50m layer salinity values for10months,15months，11months，11months. This theoretically PN section of salinity on the response of ENSO lag time ofabout one year was relatively close; The PDO index ahead of PN sectional spring,summer，autumn, winter at less than300meters, salinity eigenvalues were8months,6months,3months，8months.(7) PN section salinity has obvious seasonal variation: surface salinity summer has low winter high, spring and autumn is transition season, but as the depth increases,the salinity of the seasonal difference is getting smaller and smaller.