Sea Surface Salinity Variability And Its Different Between Two Phasees Of PDO In The Northern Pacific

The sea surface salinity(SSS)is analyzed by using SODA(version: 3.3.1)reanalysis data in the northern Pacific.Results illustrate that:(1)In the northern Pacific salinity trends to be increased from 1914 to 2013 with 30-year variability period.However,after 1979,SSS presents decreased tendency with 7-to-12-year period in the northern Pacific.(2)There are two key regions of SSS variability in the northern Pacific,which are located in the middle of the northern Pacific(A)and the middle East(B).Both the two regions can indicate the temporal change in the northern Pacific SSS.The SSS in the key regions are significantly related to the fresh water flux(FWF)in the northern Pacific.SSS in the region A is greatly affected by the local FWF,and the maximum correlation coefficient is 0.56 when FWF leads 16 month.While in the region B,the relationship between SSS and the local FWF is not significant,with the value of-0.21 and 20-month leading of the FWF.In addition,SSS and FWF have positive correlation in the region A.The main positive area occurred in the eastern extension part of the Kuroshio,with the peak value located at the middle of the northern Pacific.The large-value area moved eastward with the shortening time of leading FWF phase.SSS in the region B is positively related to that of the central northern Pacific.The most significant area is located west of the region B without shifting.In our study,it can be concluded that in the northern Pacific SSS oscillation exist obvious inter-decadal features and SSS climate variability in the northern Pacific can be represented by the changes of SSS in the key areas.Furthermore,it can also be served as an index of the FWF variability in the northern Pacific.(3)In previous study,the SSS change time point is similar to the PDO phase change,so a cool phase and a warm phase of PDO are selected for analysis(1947-1979 and 1979-2003).When the cool and warm phase of PDO,SSS show different variation trend,with the warm phase increase and the cool phase decrease.The reasons for the different trend are analyzed.The EOF second mode is used to partition the north Pacific.The results show that when FWF is ahead of SSS,the cool phase is negatively correlation and the warm phase is positively correlation.Such a contrary correlation makes the change of SSS show an opposite trend in the PDO different phase.