Chukchi Sea is the only pathway for the water in the northern Pacific Ocean into the Arctic.For a better understanding of the seasonal characteristics of the Pacific inflow on the Chukchi Shelf the spatial distribution and seasonal variability of the current through the main passage on the Chukchi Shelf were investigated using GLORYS12V1 reanalysis product from 1993 to 2020.The climatological mean showed that the Pacific inflow through the Bering Strait into the Chukchi Sea was mainly via Herald Valley,Central Channel,Barrow Canyon,and Long Strait,and the transport of each outflow accounted for 50.3％,25％,16％,and 6.9％of the Bering Strait throughflow,respectively.The seasonal variations revealed that the monthly transport at Bering Strait and Long Strait sections reached the maximum in May while the other sections peaked in July.The southeastward coastal current in the west of Long Strait section was strongest in fall.The combined empirical orthogonal function(cEOF)analysis was conducted on the velocities at 5 m and 30 m and yielded similar results,shedding light on the consistency in vertical structure.The first mode of cEOF show an in-phase variation in the whole region with high values in the four main pathways,and its time series varied out-of-phase during winter and summer half-years.The second mode mainly indicate the out-of-phase variation of the current along the Siberian coast during first and latter half-years.By decomposing the transport time series at each section into wind-related and non-wind-related components,it was found that,the non-wind factors had mainly a positive contribution while the wind contributed negatively,and the non-wind factors caused(0.23～1.33)×106 m3/s of water volume,expect for the dominant contribution of the wind at Long Strait,although the influences from wind and non-wind factors were different at these sections.The composite sea level pressure and wind fields determined that,the strength variability of northeasterly wind during summer and winter was caused by the variation in the pressure gradient between the Beaufort High and Aleutian Low,which was affected the weaken/strengthen of northward flow on central Chukchi Shelf in winter/summer.However,the current variation along the Siberian coast in spring and fall was mainly due to the zonal migration of Beaufort High and Aleutian Low.
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