Stronger intraseasonal variability observed below the seasonal thermocline in the Kuroshio east of Taiwan during 2014 and 2015

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

Journal of Oceanology and Limnology ◽

10.1007/s00343-020-9286-3 ◽

2020 ◽

Vol 38 (5) ◽

pp. 1408-1420

Author(s):

Qiang Ren ◽

Fei Yu ◽

Feng Nan ◽

Jianfeng Wang ◽

Anqi Xu

Keyword(s):

Intraseasonal Variability ◽

The Kuroshio

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A Method for Data Processing to Obtain High-Quality XCTD Data

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2011jtecho795.1 ◽

2011 ◽

Vol 28 (6) ◽

pp. 816-826 ◽

Cited By ~ 7

Author(s):

Hiroshi Uchida ◽

Koji Shimada ◽

Takeshi Kawano

Keyword(s):

Data Processing ◽

Pressure Sensors ◽

Terminal Velocity ◽

Temperature Data ◽

Quality Data ◽

High Quality ◽

Seasonal Thermocline ◽

Data Processing Method ◽

Salinity Data ◽

The Kuroshio

Abstract A data processing method to obtain high-quality data from an expendable conductivity–temperature–depth (XCTD) profiler is proposed. By adjusting the mismatch of the response time of the temperature and conductivity sensors, systematic error (on the order of −0.05) in XCTD salinity data can be eliminated from regions having a strong vertical temperature gradient (>0.2°C m−1), such as the main thermocline of the nearshore side of the Kuroshio axis and the seasonal thermocline of the subarctic North Pacific. The systematic errors in XCTD depth and temperature data from two cruises were evaluated by comparing the CTD and XCTD data taken simultaneously during each cruise. The XCTD depths were in good agreement with the CTD depths from one cruise, but depth-dependent depth errors from the other cruise were found. The cause of the depth error is unknown but may have occurred because the terminal velocity for the XCTD probes was much less (−0.0428 m s−1) than that provided by the manufacturer for the later cruise. The results suggest that XCTD and expendable bathythermograph (XBT) observations may have a similar depth error because XBT and XCTD do not have pressure sensors, and therefore depth is inferred from the fall rate of the probe. Systematic positive biases (0.018°C on average) were found in XCTD temperature data. The viscous heating effect may contribute to the thermal bias because flow past the XCTD temperature probe is relatively fast (>3 m s−1). Evaluation of XBT/XCTD data by using simultaneous CTD observations data is valuable for validation of statistical corrections of the global XBT/XCTD dataset.

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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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Eddy-Induced Heat Transport in the Subtropical North Pacific from Argo, TMI, and Altimetry Measurements

Journal of Physical Oceanography ◽

10.1175/jpo2696.1 ◽

2005 ◽

Vol 35 (4) ◽

pp. 458-473 ◽

Cited By ~ 90

Author(s):

Bo Qiu ◽

Shuiming Chen

Keyword(s):

Heat Transport ◽

North Pacific ◽

North Pacific Ocean ◽

Kuroshio Extension ◽

Heat Fluxes ◽

Seasonal Thermocline ◽

Basin Scale ◽

Turbulent Closure ◽

Eddy Heat Transport ◽

The Kuroshio

Abstract Basin-scale heat transport induced by mesoscale oceanic eddies is estimated by combining satellite-derived sea surface height and temperature [temperature data are from the TRMM Microwave Imager (TMI)] data with Argo float temperature–salinity data. In the North Pacific Ocean subtropical gyre, warm (cold) temperature anomalies of mesoscale eddies are found to be consistently located to the west of high (low) SSH anomalies. The phase misalignment between the temperature and velocity anomalies, however, is largely confined to the seasonal thermocline, causing most of the eddy-induced heat transport to be carried in the surface 200-m layer. By establishing a statistical relationship between the surface and depth-integrated values of the eddy heat transport, the basin-scale eddy heat transport is derived from the concurrent satellite SSH/SST data of the past six years. In the Kuroshio Extension region, the meandering zonal jet is found to generate oppositely signed eddy heat fluxes. As a result, the zonally integrated poleward heat transport associated with the Kuroshio Extension is at a level O(0.1 PW), smaller than the previous estimates based on turbulent closure schemes. Large poleward eddy heat transport is also found in the subtropical North Pacific along a southwest–northeast-tilting band between Taiwan and the Midway Islands. This band corresponds to the region of the subtropical front, and it is argued that the relevant temperature field for identifying this band in the turbulent closure scheme models should be that averaged over the seasonal thermocline.

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The influence of submesoscale eddies on hydrochemical parameters and structural and functional characteristics of phytoplankton in the north-eastern part of the Black Sea

Hydrosphere Еcology (Экология гидросферы) ◽

10.33624/2587-9367-2019-1(3)-24-40 ◽

2019 ◽

pp. 24-40

Author(s):

Sergey B. Kuklev ◽

Vladimir A. Silkin ◽

Valeriy K. Chasovnikov ◽

Andrey G. Zatsepin ◽

Larisa A. Pautova ◽

...

Keyword(s):

Anticyclonic Eddy ◽

The Black Sea ◽

Hydrochemical Parameters ◽

North East ◽

The North ◽

Seasonal Thermocline ◽

North Eastern ◽

Quantitative Indicators ◽

The City ◽

North Eastern Part

On June 7, 2018, a sub-mesoscale anticyclonic eddy induced by the wind (north-east) was registered on the shelf in the area of the city of Gelendzhik. With the help of field multidisciplinary expedition ship surveys, it was shown that this eddy exists in the layer above the seasonal thermocline. At the periphery of the eddy weak variability of hydrochemical parameters and quantitative indicators of phytoplankton were recorded. The result of the formation of such eddy structure was a shift in the structure of phytoplankton – the annual observed coccolithophores bloom was not registered.

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