The Influence Of Near Equator North Pacific Low PV Water On Equator Subsurface Layer

Using SODA2.2.4 ocean reanalysis data,the climatic effects and characteristics of low potential vorticity(PV)water masses,the distiribution of annual subduction rate,and their transport passages in the North Pacific are calculated from year 1871 to 2008.A newly found Near Equator low PV water(NELPVW)is defined in this study.With MV-EOF method,the sea surface and subsuirface temperature characteristies in the equatorial Pacific were studied.And the transport passages of low PV watcer masses to the equattor aceompanied with the impact s on the equatorial Pacific subsurface are discussed.The main conclusions are as fol lows:When analyzing the distribution of annual subduct ion rate in the North Pacific,an undiscovered large subduction rate value area appears in the range of 11°-17° N and 150°E-180°.The cause of the newly discoveered large subduction rate area is that there are strong horizontal process because of the oceanie boundary current and deep mixing layer,which are similar with the ARGO oceanic float observation.There are also a large number of low-PV water masses in this region,which are named as NELPVW in this thesis.NELPVW has different characteristies from other low PV water masses i n the North Pacific.As the nearest low PV water mass to the equatorial Pacifie,its temperature is the highest wi th smallest potential density.NELPVW has obvious changes on the seasonal,interannual and interdecadal time scales,and it is the second largest water mass in the four low PV water masses in the North Pacific.The maximum volume of NELPVW appears around March,with significant period of 7 and 20 years.In addition,accompanied with the global warming,obvious increasing trend is found for the NELPVW.The Lagrangian water mass tracking method is also used in this study,which proved that the eastern mode water(EMW)and NELPVW can directly affect the equatorial subsurface oceanic temperature(SOT).Two oceanic transport passages of EMW are found as the Central-EMW and Western-EMW passages.And another two oceanic transport passages are named as the Western-NELPVW and Eastern-NELPVW passages for NELPVW respectively.Specific water mass tracing shows that the EMW brings SST anomalies to the Equatorial Pacific through the Central-EMW and Western-EMW passages in 7 years.However,the NELPVW brings SST anomalies to the equator through the Western-NELPVW and Eastern-NELPVW in only3 yearsThe annual subduction process was divided into strong/weak events in the EMW and NELPVW formation regions.In the years with strong subduction process for the EMW,the SOT shows a dipole pattern with warm in the West but cold in the east,which is the negative phase of the first MV-EOF mode of SOT near the equator.However,during the years with strong subduction process in the NELPVW formation region,the SOT in the equator subsurface ocean of Pacific appears a cold anomaly in the central and eastern Pacific,which may be a combination of the positive phase of the first MV-EOF and the negative phase of the second modes of SOT.