The Meridional Volume Transport Of Circulation In The Tropical Northwest Pacific Ocean

The newly gridded Argo Profiling float data during the period of Jan.2004.to Dec.2009are used to construct the absolute geostrophic velocity field in the WesternNorth Pacific by using P-vector method. combining data analyzing and OFES model,the3-D structure, the seasonal and interannual variability are studied. The Sverdrupcirculation volume transport is compared with the meridional absolute geostrophiccurrent transport in the western north pacific to verify the Sverdrup Balance theory.Some new results are obtained which are listed as follows:(1) A set of absolute geostrophic velocity is obtained. Compared with the altimeterand TRITON data, the P-vector AGC can be used to evaluate the Sverdrup balanceand to study the three-dimensional structure of the North Pacific Ocean circulation.(2) The3D structure shows that it is consistent with previous study. The zonalgeostrophic currents based on the Argo data are found to be stronger than those basedon the traditional WOA09data. North equatorial current (NEC), North equatorialcountercurrent(NECC), Kuroshio recirculation(KR) and Kuroshio extension(KE) allshow obviously seasonal signal with strong in spring (NECC,NEC) and weak in fall,while the opposite phase in KE and KE. The significant interannual variations can befound in the NECC，NEC, KR and KE, but the NECC and NEC show a periodicinterannual signal and the KE and KR are aperiodic. In addition, the quasi180-dayoscillation of the NECC and NEC may exist. The surface NEC max velocity, currentcore position also display strong interannual variation. The current core and south boundary position of the NEC have southward trend, and moreover the NEC, KE andKR transports increase gradually.(3) There is a strong nonlinear ocean transport mechanism in the tropical northwestPacific. By compared the meridional absolutely geostrophic volume transport with theSverdrup circulation volume transport we find it has about10-20Sv difference. Aftercarefully analyzed, it is found that the nonlinear of the ocean circulation may be themain reason.