1:45 PM - 2:05 PM
[ACG44-01] The Kuroshio Large Meander since 2017: its beginnig, continuation, and future
★Invited Papers
Keywords:kuroshio Large Meander, ocean prediction, scale interaction
The Kuroshio Large Meander, which began in 2017, has lasted about four years and seven months at the time of writing this abstract. It is on the edge of surpassing the four years and eight months of the 1975-1980 period, the longest in observational history. It has been pointed out that this Large Meander could be related to the modulation of marine species, storm surges, snowfall caused by low pressure systems along south coast of Japan, and high humidity and temperatures in the Kanto and Tokai regions in summer.
The Large Meander in 2017 was initiated by the development of a small meander. This is the same mechanism as the development of previous Large Meanders. On the other hand, it showed an unprecedented beginning with the Kuroshio Current flowing south of Hachijo island (offshore path).
The Kuroshio Large meander since 2017 did not always follow the same path for over four years. From the beginning of the Kuroshio Current Great Meandering until the first half of 2018, the channel often showed an atypical flow path passing south of Hachijo island. From the second half of 2018, the meander moved westward. This westward movement enhanced the impact of the coastal return flow. Meanwhile, cold eddies often detached from the Kuroshio Large Meander. Especially, the eddy detachment in October 2020 was significant, and the large meander path temporarily ceased until the meander resumed later. A large-scale detachment of the cold eddy also occurred in February 2022, and its influence on the flow path will be closely watched. If the essence of the Large Meander is a large-scale eddy, scale interaction with smaller eddies is involved in its growth, maintenance, and decay.
The reason for the long duration of the current Large Meander is thought to be that the Kuroshio Current is too weak to push the cold eddy eastward. According to the Japan Meteorological Agency's observation along 137-degree E, the transport of the Kuroshio increased from the 1970s to the 1980s, and then decreased in the 1990s. This could be the reason for the prolonged Kuroshio Large meander. This decrease of the transport could affect the frequency and duration of future Kuroshio Large Meanders.
The Large Meander in 2017 was initiated by the development of a small meander. This is the same mechanism as the development of previous Large Meanders. On the other hand, it showed an unprecedented beginning with the Kuroshio Current flowing south of Hachijo island (offshore path).
The Kuroshio Large meander since 2017 did not always follow the same path for over four years. From the beginning of the Kuroshio Current Great Meandering until the first half of 2018, the channel often showed an atypical flow path passing south of Hachijo island. From the second half of 2018, the meander moved westward. This westward movement enhanced the impact of the coastal return flow. Meanwhile, cold eddies often detached from the Kuroshio Large Meander. Especially, the eddy detachment in October 2020 was significant, and the large meander path temporarily ceased until the meander resumed later. A large-scale detachment of the cold eddy also occurred in February 2022, and its influence on the flow path will be closely watched. If the essence of the Large Meander is a large-scale eddy, scale interaction with smaller eddies is involved in its growth, maintenance, and decay.
The reason for the long duration of the current Large Meander is thought to be that the Kuroshio Current is too weak to push the cold eddy eastward. According to the Japan Meteorological Agency's observation along 137-degree E, the transport of the Kuroshio increased from the 1970s to the 1980s, and then decreased in the 1990s. This could be the reason for the prolonged Kuroshio Large meander. This decrease of the transport could affect the frequency and duration of future Kuroshio Large Meanders.