| Three Kuroshio small meanders occurred off the southeast coast of Kyushu during 1994 to 1995 were investigated by using satellite-derived sea surface temperature (SST) and sea surface height (SSH) maps, World Ocean Circulation Experiment (WOCE) Hydrographic Program (WHP) repeat section and Japan Marine Agency (JMA) hydrographic observations. Based on consecutive satellite images, we found that these small meanders are formed in different ways: one small meander is generated by the collision of a cyclonic eddy propagated from the Kuroshio recirculation region with the Kuroshio, and the others are formed through the rapid amplification of a small-scale offshore displacement of the Kuroshio axis off the southeast of Tanega-shima Island. The amplification coincided with, in one case, the arrival of Kuroshio front meanders traveled from the East China Sea and, in the other case, the coalescence of a cyclonic eddy propagated from the east into the Kuroshio. Focusing on two small meanders in 1994 and 1995 spring, which are captured by the WHP repeat observation, we investigated structures and water characteristics of the small meanders. These two small meanders show quite consistent hydrographic features despite their different formation processes. On the nearshore side of the meandering Kuroshio, a countercurrent appears dominantly. This countercurrent is associated with vertically uniform upward lifts of the isopycnals from sea surface to bottom at the boundary between the countercurrent and the Kuroshio. In the countercurrent region, the waters in the density ranges of North Pacific Subtropical Mode Water (NPSTMW) and North Pacific Intermediate Water (NPIW) are more saline and less saline than typical waters that the Kuroshio carries in a non-small meander state, respectively. It was indicated that high-salinity NPSTMW and low-salinity NPIW distributed off the Kuroshio should be supplied to the countercurrent region. In the meandering Kuroshio flow, while there is no notable change in properties around the NPSTMW density range, salinity of NPIW is significantly higher than that carried by the Kuroshio in a non-small meander state. The salinity value of this NPIW is comparable to or less than that of the Kuroshio at the Tokara Strait, suggesting that saline NPIW from the East China Sea, less mixed with low-salinity NPIW off the Kuroshio, may be carried by the meandering Kuroshio. |
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