Variation of the Kuroshio south of Japan

Nitani, Hideo

doi:10.1007/bf02107107

Cited by 69 publications

(2 citation statements)

References 8 publications

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“…The period of the largest peak in the power spectrum of the Y b_vol is around 73 days (Figure 4a) . As the MJO is the dominant mode of the ISV with periods of 30-90 days in the tropical atmosphere (Madden & Julian, 1971, 1972Zhang, 2005), and it perturbs the upper ocean through surface fluxes of momentum, latent and sensible heat, radiation, and fresh water (e.g., Hendon & Glick, 1997;Jones et al, 1998;Krishnamurti et al, 1988;Lau & Sui, 1997;Zhang, 1996). We first investigate the relationship between the MJO and the ISV of the NEC bifurcation.…”

Section: The Relationship With the Mjomentioning

confidence: 99%

Intraseasonal Variability of the North Equatorial Current Bifurcation Off the Philippines

Zou

Liu

Li³

et al. 2021

JGR Oceans

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Characteristics of the intraseasonal variability (ISV) of the North Equatorial Current bifurcation latitude (NBL) are analyzed by using both observations and reanalysis data. The maximum amplitude of the ISV of the NBL can reach about 6° of latitude, which almost triples its annual excursion. The NBL shows a broad spectral peak around 50–140 days with the highest peak occurring around 73 days. Both the Madden‐Julian oscillation and mesoscale eddies have a significant impact on its ISV. A case study for a cyclonic eddy indicates that it can transport about 1.5 Sv (1 Sv–106 m3 s−1) waters to the NBL, and the bifurcation shifts northward with an amplitude of about 8° of latitude in 1 month. Meanwhile, the influence of mesoscale eddies on the ISV of the NBL is highly modulated by the interannual variations of the eddy field. Active eddy activities associated with enhanced barotropic and baroclinic instabilities show a large influence on the NBL. The eddy kinetic energy level around the NBL showed a quite diverse character for the 1997–1998 and the 2015–2016 extreme El Niños, with the latter being double or triple that of the former due to the much stronger vertical and horizontal shears. Given the significant impact on the NBL by the individual eddies and the unevenly distributed cyclonic and anticyclonic eddies around the NBL, the effect of mesoscale eddies on the bifurcation latitude may not cancel each other on seasonal or interannual time scales.

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Section: The Relationship With the Mjomentioning

confidence: 99%

Intraseasonal Variability of the North Equatorial Current Bifurcation Off the Philippines

Zou

Liu

Li³

et al. 2021

JGR Oceans

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“…The physical properties of ocean currents are investigated by shipboard and satellite observations and profiling floats. The observation of the KC started during the World War II, but this campaign is sporadic (Kawakami et al., 2022; Nitani, 1975). Recently, the high‐resolution systematic oceanic investigation for the KC by Argo profiling floats, covering the last 20 years.…”

Section: Introductionmentioning

confidence: 99%

Anthropocene North Western Pacific Oceanography Recorded as Seasonal‐Resolution Radiocarbon in Coral From Kikai Island, Japan

Zeng,

Yokoyama,

Hirabayashi

et al. 2024

Global Biogeochemical Cycles

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Radiocarbon (14C) in corals can be used as a relatively high‐sensitivity indicator of vertical and horizontal advection of water masses, which contributes to the understanding of ocean circulation. In this study, we reconstruct Kuroshio and Ryukyu current transport with a seasonal resolution Δ14C record spanning 1947–2009. This record covers the beginning of the atomic era and was obtained from a coral on Kikai Island in the south of Japan. The Kikai Δ14C curve features a newly discovered Δ14C spike in July 1955, a rapid increase after 1962, and a steady decrease after 1980. The spike in 1955 may directly reflect ocean current transport. The lack of periodicity in the Δ14C record suggests the existence of mesoscale eddies and the complexity of Kuroshio and Ryukyu current transport. In addition, comparing the high‐resolution Δ14C of Kikai and Ishigaki islands, both situated along the path of the Kuroshio, reveals the influence of Pacific Decadal Oscillation and El Niño‐Southern Oscillation on the Kuroshio and Ryukyu currents. This suggests that seasonally resolved Δ14C in corals along an ocean current can produce a long‐term record of ocean mixing that responds to climate variability.

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Distinguishing meanders of the Kuroshio using machine learning

2014

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The Kuroshio south of Japan is often described as being bimodal, with abrupt transitions between a straight path state that stays near the coast (small meander) and a meandering state that deviates from the coast (large meander). Despite evidence of the existence of two or more states of the Kuroshio, previous data-driven studies have shown only high variability of the current; they have not, however, demonstrated bimodality in the sense of two states of relatively high probability separated by a region of relatively low probability. We use singular value decomposition (SVD), a standard time series analysis method for characterizing variability, and diffusion maps and spectral clustering (DMSC), a machine learning algorithm that seeks multimodality, to investigate Kuroshio reanalysis output. By applying these methods to a time series of velocity fields, we find that (1) the Kuroshio is bimodal, with high inflow and low path variability in the small meander and low inflow and high path variability in the large meander, (2) the state of the system correlates highly with the location of the recirculation gyre south of Japan, and (3) the meanders are better characterized by path variability than by mean path. Because these results are consistent with satellite sea surface height data, they are not an artifact of the model used for reanalysis. Further, our results provide evidence for a previously proposed transition mechanism based on the strengthening, migration, and weakening of the recirculation gyre south of Japan and can therefore help direct future modeling studies.

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Variation of the Kuroshio south of Japan

Cited by 69 publications

References 8 publications

Intraseasonal Variability of the North Equatorial Current Bifurcation Off the Philippines

Intraseasonal Variability of the North Equatorial Current Bifurcation Off the Philippines

Anthropocene North Western Pacific Oceanography Recorded as Seasonal‐Resolution Radiocarbon in Coral From Kikai Island, Japan

Distinguishing meanders of the Kuroshio using machine learning

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