Characteristic And Mechanisms Of Sea Surface Temperature Low Frequency Variability In The Offshore Sea Of China

Latest observational, reanalysis and higher resolution ocean model data are used tostudy the spatial and temporal variability of sea surface temperature in the marginal seasof China. Low frequency variability and mechanisms of sea surface temperature in bothwinter and summer are analyzed, with discussing the role of oceanic advection andair-sea heat flux. The conclusions are drawn as follows:(1)Sea surface temperature in the marginal seas of China displays an obviouswarming trend from1900to2010, and experienced a climate shift during1970to1980after which there is an increasing warm ra than before. The area with the fastest warmingrate is along the path of Kuroshio and the continental shelf warm current, and also inChangjiang Estuary. On the whole, oceanic advection plays a warming effect while thenet surface heat flux plays a cooling effect on the variations of SST. The change of SSTperhaps has a close relation with wind stress curl in middle latitude of North Pacific, andthe Kuroshio transport has a2-3yr or7-9yr lag with the stress curl. The delay response isin accord with the time that Rossby waves propagate from the east to the west PacificOcean.(2)During the past century, Sea surface temperature in winter and summer alsodisplays an obvious warming trend, and after1970-1980there is an increasing warmrate than before. Maybe because of stronger gradient, SST in winter increases morestrongly than in summer and annual mean data. The depth of area with the fastestwarming rate of SST in winter is deep, but shallow in summer. Along the path ofKuroshio and the continental shelf warm current, net surface heat flux plays a coolingeffect on winter SST’s change, but warming in the east of Kuroshio. And different datashows that net surface heat flux have warming and cooling work on the change of SST insummer.(3)In decadal scales, the first EOF mode is characterized by uniform warming overthe offshore sea of China, which is related to global warming. Except ERA_interim data, other data all show that the second EOF mode indicates a variation trend with the SST inthe Kuroshio area out of phase with that in other area, or a variation trend with the SST inBohai Sea, Yellow Sea, and East China Sea out of phase with that in other area. Thesecond principle component is associated with PDO index. The oceanic advection play awarming effect while the net surface heat fluxplays a cooling effect on the first twoEOF mode of SST.(4)In decadal scales, the first EOF mode indicates the characteristics of SSTvariation in both winter and summer time trending to uniformity, and the first principlecomponent is related to global warming displaying a significant warming trend. ExceptERA_interim data, other data all show that the second EOF mode indicates a variationtrend with the SST in both winter and summer in the Kuroshio area out of phase with thatin other area. It is worth noting that the second principle component in winter isassociated with PDO index, but that in summer is related to both PDO and AMO index.The Oceanic advetion has a warming effect while the net surface heat flux has adamping effect on the first two EOF modes in winter and the first EOF mode in summeralong the path of Kuroshio and the continental shelf warm current.But other data all showthat net surface heat flux has a warming role on the second EOF mode in summer, exceptMERRA data,and oceanic advection has a cooling effect in summer.. Moreover, themagnitude of oceanic advection in winter is much bigger than that in summer.