An Analysis Of Characteristics Of Eddies Shedding From Kuroshio In The Luzon Strait

The Kuroshio is the strongest western boundary currents of the northwest Pacific Ocean.During flowing northward along the west shore of the Pacific the Kuroshio water can partially enter the South China Sea(SCS)through the Luzon Strait,and thus influences the marine environment of the northern SCS,even the entire SCS.The eddy shedding from the Kuroshio is one of the ways of the intrusion of the Kuroshio water into the SCS.In order to make a statistical analysis of eddies that shed from Kuroshio in the Luzon Strait area and enter into the South China Sea,we mainly use 22 years(1993—2014)of global gridded multi-satellite merged sea level anomaly and absolute dynamic topography products in delay time provided by Archiving,Validation,and Interpretation of Satellite Oceanographic data(AVISO)to statistically analyze the behaviors of the eddies shedding from the Kuroshio in the Luzon Strait and entering the SCS,and their relation with the large-scale circulation.In the study the climatological mean temperature and salinity profiles of World Ocean Atlas2013(WOA13)data provided by National Oceanographic Data Center(NODC)and the monthly SODA2.2.4 date set from 1993 to 2010 are also utilized.The results suggest that:(1)As compared to the shedding cold eddies(CEs),the shedding warm eddies(WEs)are much greater in number;The most CEs are formed at the western edge of the Kuroshio,while the most WEs are formed within the Kuroshio-controlled areas.(2)The average radius and average amplitude of CEs and WEs are similar,but the average lifetime and average migration distance of CEs are almost a half of those of WE respectively.(3)WEs shed all the year round and mostly in autumn,while CEs do not shed every year and mostly shed in winter.(4)Besides,the amount of the shedding eddies is related to the path types of Kuroshio at the shedding time,becausethe Kuroshio shed more eddies at the leaking path than at the other paths.(5)The average westward speed of shedding eddies is 5.8 cm/s,which is roughly equal to the sum of the mean first baroclinic Rossby wave phase speed and the mean west component of the large-scale circulation currents.For a comparison and as a supplement,we further utilize the OGCM for the Earth Simulator(OFES)model product from 1993 to 2013 to analyze the behaviors of the shedding eddies from the Kuroshio,and to study the three-dimensional structures of their current,temperature and salinity.The results suggest that:(1)The shedding WEs are much greater in number than the shedding CEs;The most CEs are formed at the western edge of the Kuroshio,while the most WEs are formed within the Kuroshio-controlled areas.This feature is consistent with that observed from satellite,but the numbers and occurrence frequencies are much lower than the altimeter observations.(2)The vertical scales of the CEs are shown to rely on their formation sources,while the vertical scales of the WEs can reach over 1000 m.(3)The temperature and salinity structure of the shedding eddies is greatly affected by the Kuroshio.