Intraseasonal variability of the Kuroshio east of Taiwan, China, observed by subsurface mooring during 2016–2017

Abstract Based on direct measurements of the Kuroshio current velocity at 18°N by an array of three moorings from January 2018 to February 2020, the intraseasonal variability (ISV) of the Kuroshio and possible dynamic mechanism are studied. The Kuroshio transport in the upper 350m between 122.7°E and 123.3°E is estimated to be 6.5 Sv ± 2.6 Sv. It is revealed for the first time that both the current velocity and volume transport the Kuroshio at 18°N have a significant 50-60-day ISV, which contributes to over 30% of the total variance. Further analysis indicates the ISV of the Kuroshio is caused by the westward propagating eddies with a wavelength of about 633 km and a propagation speed of about 13 cm/s. In addition, the transport mode (74.2%) of the Kuroshio at 18°N is dominant, rather than the migration mode (11.6%). That is different from the Kuroshio east of Taiwan. The findings of this study will highlight the important role of westward Rossby waves (eddies) with a finite wavelength in modulating the intraseasonal variability of the Kuroshio transport near its origin.

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Effects of Mesoscale Eddies On Intraseasonal Variability of Intermediate Water East of Taiwan

10.21203/rs.3.rs-1198576/v1 ◽

2022 ◽

Author(s):

Qiang Ren ◽

Fei Yu ◽

Feng Nan ◽

Yuanlong Li ◽

Jianfeng Wang ◽

...

Keyword(s):

Intermediate Layer ◽

Intraseasonal Variability ◽

Correlation Coefficients ◽

Mesoscale Eddies ◽

Vertical Movement ◽

Intermediate Water ◽

Sea Level Anomalies ◽

Anticyclonic Eddies ◽

Counter Current ◽

The Kuroshio

Abstract The variability of intermediate water (IW) east of Taiwan was investigated utilizing 17 months of long-term, continuous and synchronous measurements of temperature, salinity and current from mooring sites deployed at 122ºE/23ºN from January 2016 to May 2017. For the first time, we prove that the intraseasonal variability in the IW within significant periods of ~80 days was caused by mesoscale eddies propagating westward from the Subtropic Counter Current (STCC) area. The correlation coefficients between sea level anomalies (SLAs) and the Kuroshio, and between SLAs and the minimum salinity in the intermediate layer, were 0.63 and 0.52, respectively. The anticyclonic (cyclonic) eddies from the STCC, increased (decreased) the speed of the Kuroshio as well as increase (decrease) the temperature and salinity in the 400–600 m in east of Taiwan. Combines Archiving, Validation and Interpretation of Satellite Oceanographic (AVISO) products data, showed that temperature and salinity increased (decreased) in the intermediate layer due to the downward (upward) vertical movement of the water mass by anticyclonic (cyclonic) eddies. Anticyclonic eddies strengthened the Kuroshio and benefitted SCSIW flowing through the Luzon Strait to enhance salinity, while cyclonic eddies weakened the Kuroshio and favored relatively low-salt NPIW, in the area east of Taiwan.

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Internal Tides and Their Intraseasonal Variability on the Continental Slope Northeast of Taiwan Island Derived from Mooring Observations and Satellite Data

Remote Sensing ◽

10.3390/rs14010059 ◽

2021 ◽

Vol 14 (1) ◽

pp. 59

Author(s):

Yuqi Yin ◽

Ze Liu ◽

Yuanzhi Zhang ◽

Qinqin Chu ◽

Xihui Liu ◽

...

Keyword(s):

Continental Slope ◽

Satellite Data ◽

Bottom Topography ◽

Intraseasonal Variability ◽

Mesoscale Eddies ◽

Kuroshio Current ◽

Internal Tides ◽

Taiwan Island ◽

The Impact ◽

The Kuroshio

In this study, strong internal tides were observed on the continental slope northeast of Taiwan Island. Owing to the lack of long-term observations, these tides’ intraseasonal variability and the impact of the Kuroshio Current remain unclear. This study aimed to fill in the gaps using one-year continuous mooring observations, satellite data and analysis data. The horizontal kinetic energy (HKE) of semidiurnal internal tides showed that there was conspicuous energy from 100 days to 200 days, which was mainly attributed to the cross-term of HKE. The impact of the Kuroshio Current and mesoscale eddies on the HKEs were assessed: Cyclonic (anticyclonic) mesoscale eddies propagated from the open ocean, weakened (strengthened) the Kuroshio and shifted the Kuroshio onshore (offshore) northeast of Taiwan Island. The weakened (strengthened) Kuroshio increased (decreased) the shoreward velocity at the mooring site, and the onshore (offshore) Kuroshio migration increased (decreased) the northeastward velocity and enhanced (weakened) the HKEs of internal tides by modulating the tidal energy horizontal propagation. The weakened (strengthened) Kuroshio also resulted in gentler (steeper) isopycnals across the slope and enhanced (weakened) the HKEs of internal tides by influencing the interaction between ocean stratification and bottom topography.

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