基于GLORYS12V1再分析数据的楚科奇陆架区流场季节变化特征分析

SEASONAL VARIABILITY OF CURRENT ON THE CHUKCHI SHELF BASED ON GLORYS12V1 REANALYSIS

楚科奇海是北太平洋海水进入北冰洋的唯一通道,为更好地了解北太平洋入流水在陆架区流场的季节变化特征,本文基于1993~2020年的GLORYS12V1再分析数据,对楚科奇陆架区流场的空间分布和关键通道断面流场季节变化特征进行了分析。气候态平均结果显示,太平洋入流水通过白令海峡进入楚科奇海后主要由汉娜德海谷、中央水道、巴罗峡谷和德朗海峡断面流出陆架,四支路径的流量占白令海峡入流的比例分别为50.3%、25%、16%和6.9%。季节变化结果显示,白令海峡和德朗海峡断面流量的月变化在5月达最大,其余断面则在7月达峰值。德朗海峡断面西侧东南向沿岸流在秋季最强。5 m和30 m流速的联合经验正交函数分解的模态较为类似,体现了垂向结构的一致性。第一模态的空间分布显示整个研究区域均为同位相分布,且四支主要路径上呈现高值,其时间序列在冬夏半年呈反位相变化。第二模态主要体现陆架区西侧西伯利亚沿岸流场的上下半年呈反位相变化。将各断面的流量序列分解为与风相关的部分和非风因素相关的部分进行分析发现,气候态平均流量除德朗海峡处风起主要贡献外,其余断面均为非风因素对流量起正贡献而风起负贡献,非风因素引起的流量达0.23×10^(6)~1.33×10^(6) m^(3)/s,不过风和非风因素对各断面季节变化特征的影响并不一致。气压场和风场季节变化的分析结果显示,夏冬季波弗特高压和阿留申低压之间气压差的变化导致了东北风强度变化,进而影响了楚科奇陆架中心区冬/夏半年北向流的弱/强。而春秋季主要分别是波弗特高压和阿留申低压的东西位置变化对西伯利亚沿岸的流场产生影响。

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)×10^(6) m^(3)/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.