东海黑潮PN和TK断面流量的多时间尺度变化特征

Multi-timescale Variations of the Kuroshio Volume Transport Through PN and TK Sections in the East China Sea

根据日本海洋数据中心提供的1972—2017年PN断面共181个航次和1987—2010年TK断面共92个航次的CTD调查资料,利用动力高度法估算了这2个断面的流量,分析了其季节、年际和长期变化特征。主要结果表明,PN断面流量季节变化为冬、春和夏季大而秋季小,TK断面流量季节变化为冬、夏季大而春、秋季小,二者共同点为最大(小)流量均出现在夏(秋)季。PN断面年平均流量的年际变化不明显,但冬季和夏季流量分别具有准3 a和准2 a的显著变化周期;TK断面年平均流量具有准4 a和准6 a的显著变化周期,冬季流量具有准4 a和准7 a的显著变化周期,但夏季流量无显著变化周期。此外,PN断面流量在1976年附近出现了一次较大幅度的增加。PN断面流量具有较大的长期增加趋势,增长率约为0.3 Sv/a,在1972—2017年增加了约13 Sv,结合NCEP海面风应力资料,结果显示,北太平洋更高纬度带(35°N和40°N)的风应力旋度对PN断面流量的影响更强。

Based on the CTD measurements of 181 voyages at PN section from 1972 to 2017 and 92 voyages at TK section from 1987 to 2010,the seasonal,inter-annual and long-term variations of the Kuroshio volume transport(KVT)across the two sections are analyzed with dynamic height method.The results show that the KVT across PN section is larger in winter,spring and summer than in autumn,while the KVT across TK section is larger in winter and summer than in spring and autumn.The KVT across the two sections both reach their maximum(minimum)in summer(autumn).The significant periods of KVT vary with sections and seasons.The variation of annual mean of KVT across PN section,though not obvious,does show a 3-year period in winter and a 2-year period in summer.That of KVT across TK section shows 4-year and 6-year periods,and 4-year and 7-year periods are found in winter KVT but no significant periods in summer.The KVT across PN section shows an abrupt increase in about 1976,and a long-term increasing trend with increment of 13 Sv from 1972 to 2017 at a growth rate of 0.3 Sv per year.According to the analysis based on the NCEP sea surface wind stress data,wind stress curl has a greater impact on the KVT cross PN section at higher latitudes(35°N and 40°N)of the North Pacific.