Variability of the Kuroshio Extension jet, recirculation gyre, and mesoscale eddies on decadal time scales
Variability of the Kuroshio Extension jet, recirculation gyre, and mesoscale eddies on decadal time scales
复制标题
DOI：
10.1175/jpo2807.1
复制
发表时间：
2005-11-01
影响因子：
3.5
通讯作者：
Chen, SM
中科院分区：
文献类型：
--
作者：
Qiu, B;Chen, SM
利用12年多卫星高度计的海面高度资料，研究了黑潮延伸区急流、南环流涡旋及其中尺度涡量场的低频变化及其相互关系。主要信号是1993-1996年KE急流/环流涡旋持续减弱，1997年后逐渐增强。在1993-96年的减弱期间，KE路径总体上向南移动，1997年后KE急流和环流涡旋加强期间，这条路径的迁移方向发生了逆转。利用线性涡度动力学对SSH信号进行分析，发现KE急流和环流涡旋的减弱(加强)与北太平洋东部产生的SSH负(正)异常向西传播和向西传播过程中的加强是一致的。1996-2001年，当KE急流和环流涡旋处于弱模时，区域涡动动能水平高于急流和环流涡旋处于强模时。在SSH资料和线性涡度模式中都发现了平均气流强度与区域涡动能水平之间的负相关，这是由于KE急流在伊豆-小川脊上的迁移造成的。当受到撞击的SSH负异常的强迫向南移动时，KE急流通过一个浅段绕过脊线，导致下游的大范围迂回。另一方面，SSH正异常的撞击加强了环流涡旋，迫使流入通过深槽的地方向北移动，使下游地区的路径扰动最小化。
Twelve years of sea surface height (SSH) data from multiple satellite altimeters are used to investigate the low-frequency changes and the interconnections of the Kuroshio Extension (KE) jet, its southern recirculation gyre, and their mesoscale eddy field. The dominant signal is characterized by the steady weakening of the KE jet/recirculation gyre from 1993 to 1996, followed by a gradual strengthening after 1997. During the weakening period of 1993 - 96, the KE path migrated southward in general, and this path migration reversed in direction during the strengthening period of the KE jet and recirculation gyre after 1997. By hindcasting the SSH signals using linear vorticity dynamics, it was found that weakening ( strengthening) in the KE jet and recirculation gyre is consistent with westward propagation of negative ( positive) SSH anomalies generating in the eastern North Pacific and strengthening during their westward propagation. When the KE jet and recirculation gyre were in a weak mode during 1996 - 2001, the regional eddy kinetic energy level was observed to be higher than when the jet and recirculation gyre were in a strong mode. This negative correlation between the mean flow intensity and the level of regional eddy kinetic energy is found in both the SSH data and the linear vorticity model to result from the migration of the KE jet inflow over the Izu - Ogasawara Ridge. When it is forced southward by the impinging negative SSH anomalies, the KE jet inflow rides over the ridge through a shallow segment, leading to large-amplitude downstream meanders. Impinging of positive SSH anomalies, on the other hand, strengthens the recirculation gyre and forces the inflow northward where it passes through a deep channel, minimizing the path perturbations in the downstream region.