Since September 2017, the Kuroshio has taken a large-meander (LM) path in the region south of Japan. We examined characteristics of the 2017–present LM path in comparison with previous LM paths, using tide gauge, altimetric sea surface height, and bottom pressure data. The 2017–present LM path was formed from a path passing through a channel south of Hachijo-jima Island, while a typical LM path originated from a path through a channel north of Miyake-jima Island. The meander trough of this atypical path was found to be shifted far to the east and to vary on a timescale of months. These characteristics are different from those of a typical LM path but they are similar to those of the 1981–1984 LM path. Therefore, we identified two types of LM path; a stable and unstable LM paths. The 2017–present unstable type large meander has a zonal scale greater than that of the 2004–2005 stable type large meander and protrudes from the eastern boundary of the Shikoku Basin, i.e., Izu-Ogasawara Ridge. No significant bottom pressure depression was observed, associated with the formation of the 2017–present LM path, indicating that baroclinic instability was not important in the formation of this LM path. Due to no significant bottom steering, even during the 2017–present LM period, a mesoscale current path disturbance occurred southeast of Kyushu, propagated eastward, and amplified the offshore displacement of the Kuroshio.

中文翻译：

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2017年9月在日本南部形成的黑潮现今非典型大步道的特征

自2017年9月以来，黑潮在日本南部地区采取了大弯（LM）路线。我们使用潮汐仪，海平面高度和底部压力数据，比较了2017年至今的LM路径与以前的LM路径的特征。2017年至今的LM路径是由一条穿过八丈岛南部的通道形成的，而典型的LM路径则是源自三宅岛的北部通道。人们发现，这条非典型路径的曲折谷向东移动并在数月的时间范围内变化。这些特征与典型的LM路径不同，但与1981-1984 LM路径的特征相似。因此，我们确定了两种类型的LM路径：稳定和不稳定的LM路径。2017年至今的不稳定型大弯带的纬向尺度大于2004年至2005年的稳定型大弯带，并从四国盆地的东边界即伊豆小gas原岭突伸。没有观察到明显的底部压力下降，这与2017-至今的LM路径的形成有关，表明斜压不稳定在该LM路径的形成中并不重要。由于没有明显的底部操纵，即使在2017年至今的LM时期，九州东南部也发生了中尺度的电流路径扰动，向东传播，并扩大了黑潮的海上位移。与2017年至今的LM路径的形成相关，表明斜压不稳定在该LM路径的形成中并不重要。由于没有明显的底部操纵，即使在2017年至今的LM时期，九州东南部也发生了中尺度的电流路径扰动，向东传播，并扩大了黑潮的海上位移。与2017年至今的LM路径的形成相关，表明斜压不稳定在该LM路径的形成中并不重要。由于没有明显的底部操纵，即使在2017年至今的LM时期，九州东南部也发生了中尺度的电流路径扰动，向东传播，并扩大了黑潮的海上位移。