The Influence Of Kuroshio Current To The Boundary Circulation In Japan /East Sea

Kuroshio Current (KC) is the strongest west boundary current in the East Asian marginal seas (EAMS) . Study on the influence of KC to EAMS is the key point of understanding the ocean circulation effect on the marginal seas, and it has an important scientific and realistic meaning. Japan/East Sea (JES) is an important area of the EAMS. This area acts as a marginal sea connecting the land territory with China, Russia, North Korea, South Korea and Japan. The importance of strategic location is self-evident. Based on the previous studies, this thesis focuses on KC's influence to the boundary circulation in JES, through data analysis, theoretical derivation and numerical simulation.There are both west and east boundary currents flowing northword in JES. In this thesis, we consider that the preesure difference set by KC is the main forcing of these two boundary currents; the Insland integral constrant, the Potential Voticity (PV) integral constraint and the Mass conservation constrant are the leading dynamic mechanism on forming and mataining these two boundary currents.Based on the POM model, the NWPO circulation field is established. After model validation, the Island intergral constraint, PV integral constraint and Mass conservation constrant are introduced to explain the mechanism for the bifurcation of the Tsushima Warm Current (TSWC) into the JES. Study indicates that the volume transport of TSWC and its seasonal changes are mainly decided by open ocean process, not by the local forcing. KC flows northward along the east coast of Japan Island, sets the pressure difference (Δp) between the Tsushima Strait (TS) and Tsugaru Strait (TSS). And thisΔp is the main force of the TSWC. The water mass flows into JES through TS and flows out of JES through TSS and Soya Strait respectively. It follows the Mass conservation constrant. According to the Island intergral constraint, the west coast of Japan Island is also feels thisΔp, combines with the friction along the west coast of Japan Island, and maintains the east branch of TSWC (named Nearshore Branch, NB) .About the west branch of TSWC, it is explained by the PV integral constraint. In a semi-closed basin, the PV integral over the whole basin yields a balance between the net lateral PV inflow and the PV dissipation along the boundary. The net lateral PV inflow into the JES includes two parts: one is topographyβeffect; the other is the planetaryβeffect. The net PV advection into the JES is negative due to both bathymetrical and latitudinal differences among three straits. A frictional torque associated with a strong anti-cyclonic boundary current is required in order to balance the PV integral constraint along the boundary of JES, and this leads to the establishment of the anti-cyclonic western boundary current.On the basis of the study on mechanism, this thesis further studies the KC inter-annual variability to the JES circulation. Using the hybrid coordinates ocean model (HYCOM), the KC's monthly variations in 10 years is successfully simulated. The Island intergral constraint and Mass conservation constrant are introduced to study the mechanism of NB in interannual variability, under the situations of the KC's axis exist the large mender (LM) or non-large-meander (nLM) path. The results show when KC's axis has the LM, the NB is weaker; otherwise, when KC's axis has the nLM, the NB is stronger.The TSWC acts as the unique inflow in JES, it plays a significant role on the JES's physical process. Based on an improved POM, nesting the output of HAMSOM model, a baroclinic quasi prognostic model is built at the TS in JES. The results show that the current advects into the JES through the TS is divided into two parts by Tsushima Island. The main axis of the current at the TS obviously has double-core structure and they seasonally change their depths. The sea front exits all the season.Based on the POM, this thesis establishes several numerical experiments to study the dynamic relationship between TSWC and Taiwan Warm Current (TWC) . The research validates the existence of "TSWC-TWC system" further more. Preliminary find the source of TSWC and where TWC flows. TSWC is more important in this system, and TWC has little effect on TSWC. The possible mechanism can be explained here in terms of energy propagation by topographic waves.