| The Kuroshio is a main branch of the western boundary current in theNorth Pacific, and its path in the East China Sea is relatively stablethroughout the year. It plays an important role not only in thehydrological environment, but also in the climate change of East Asia.Among many factors influencing the Kuroshio, wind stress is obviously animportant one. Both the local and non-local wind stress have great impacton the upper layer circulation. In this thesis, the model output of MPI-ESM,a state-of-the-art Earth system model developed by Max-Planck Institutefor Meteorology in Germany, is used to analyze the variations of the windand circulation in the North Pacific Ocean in2010-2090under globalclimate change scenario RCP4.5. The model output is also utilized asforcing field to drive HAMSOM, a regional ocean model with high resolution.By selecting typical sections of the Kuroshio in the East China Sea, thevariations of the upper Kuroshio circulation and its relationship withthe local and non-local wind stress in the East China Sea, as well as thelink between them, are studied based on the results of HAMSOM model. Mainconclusions deduced are as follows:(1) Compared with today’s climate, the wind stress over the NorthPacific under global climate change scenario has the greatest changes inwinter, followed by spring, and small changes in summer and autumn. Under the combined effect of the meridional wind stress changes and thestrengthening and northward movement of the mid-latitude westerly, thewind stress curls in the North Pacific sub-polar and sub-tropic bothstrengthen.(2) In North Pacific the root mean square high value areas of the seasurface height(SSH) and wind stress are approximately in the same location,and their distributions in low latitudes are very consistent. Therefore,the changes of SSH is likely to be affected by the variations of the windstress.(3) In North Pacific, the distribution and seasonal variations of thebarotropic mass streamfunction are quite similar to the variations of thewind stress. The SVD analysis of streamfunction field and wind stress curlfield shows that there is a significant correlation between them.(4) Most changes in flow velocity of the Kuroshio in the East ChinaSea are concentrated within the upper100meters, a depth within whichthe circulations are directly affected by the wind stress. With consistentseasonal variations in each season, the transports across the three mainsections in the upper100meter from high to low are: PN>PCM1>TK.(5) The results of wavelet analysis to the upper transport of PNsection show a significant quasi-two-year period since2010. Asignificant4-8years period disappears during2030～2040, while a8-16years period, which has lower frequency, arises and persists.(6) The local wind stress in the Kuroshio region has typical monsooncharacteristics, with greater wind velocity and longer duration in winterthan in summer. The results of wavelet analysis to the interannualvariations of meridional wind stress show a quasi-two-year period and a8-year period, which are both consistent with the significant periods ofthe interannual variations of the upper transport at PN section.(7) Changes of the wind stress in the North Pacific region mainly affect the interannual and decadal variations of the upper Kurushiotransport in the East China Sea, and the wind stress curl influence theupper Kuroshio transport10months in advance. Variations of the upperKuroshio transport in summer has a good correlation with the localmeridional wind anomaly in June, and the high correlation zones are theSouth China Sea and the drainage area of the Kuroshio in the East ChinaSea, with the maximum correlation coefficient of0.642(99%confidencelevel); variations of the upper Kuroshio transport in winter has a goodcorrelation with the local meridional wind anomaly in August of theprevious year, and the high correlation zone locates in the South ChinaSea, with the maximum correlation coefficient of0.532(99%confidencelevel). |
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