Transition to the Large Meander path of the Kuroshio as observed by satellite altimetry

By combining satellite altimeter data and sea-surface drifter data, we examine the transient processes leading to the Large Meander (LM) path of the Kuroshio south of Japan in 2004, which occurred for the first time after the TOPEX/POSEIDON altimetry started in 1992. The transition to the LM path was preceded by the generation of the "trigger meander" southeast of Kyushu, which then propagated eastward south of Shikoku. After the trigger meander passed Cape Shiono-misaki, it slowed down with its trough rapidly amplified over Koshu Seamount located about 200 km to the south of Cape Shiono-misaki. Consequently, the Kuroshio meander looped back west of the Izu-Ogasawara Ridge, leading to the formation of the LM path. The time series of the Kuroshio axis from 1993 through 2005 shows that the meander trough extended over Koshu Seamount only in 2004. All of these observed features are well reproduced in the model results by Endoh and Hibiya (2001), who demonstrated the important role of baroclinic instability over Koshu Seamount in the formation of the LM path of the Kuroshio.