Kuroshio subsurface water feeds the wintertime Taiwan Warm Current on the inner East China Sea shelf

Lian, Ergang; Yang, Shouye; Wu, Hui; Yang, Chen; Li, Chao; Liu, James T.

doi:10.1002/2016jc011869

Cited by 95 publications

(68 citation statements)

References 65 publications

(159 reference statements)

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“…Both the modeled and observed phosphate concentrations in the bottom layers were higher than surface waters, with values similar to the typical phosphate concentration in the Kuroshio subsurface water (0.7–1.2 μM; Guo et al, ; Zhang et al, ). Previous studies have shown that there is a persistent Kuroshio subsurface water intrusion in the vicinity of the Changjiang River Estuary (Lian et al, ; Yang et al, ). Nevertheless, the simulated bottom phosphate values were ~20% lower than the observed data.…”

Section: Resultsmentioning

confidence: 97%

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

Wang

Lin

et al. 2019

JGR Oceans

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The occurrence of phytoplankton blooms in estuarine and coastal waters is codetermined by the export of fluvial nutrients and other water properties such as turbidity. In this study, the Changjiang River Estuary was used as an example to investigate the intrinsic link between river plume dynamics, riverine nutrient loading, suspended sediment concentration, and phytoplankton blooms with a coupled hydrodynamic-sediment-ecosystem numerical model. Suspended sediment concentration from the sediment module was used to parameterize light attenuation in waters, which, in association with river plume dynamics, was found to impact phytoplankton distribution. Data that was collected in situ, in addition to satellite data for chlorophyll, nutrients, and suspended sediments, were used to validate the model, which performed well. The surface high chlorophyll centers exhibited a patch-like pattern from the northeast to the south off the Changjiang River mouth. The high chlorophyll concentration within the river plume was mainly determined by riverine nutrient exports, and potential phosphate limitation occurred away from the river mouth. The chlorophyll concentration decreased dramatically shoreward of the sediment front, which was controlled by the bottom river plume front. The bottom plume front was an intrinsic feature of the Changjiang River plume and similar river plume systems, which set a boundary separating the well-mixed (turbid) nearshore waters and stratified (clear) offshore waters. Without considering the sediment shading effect, the model yielded an unrealistic chlorophyll distribution with artificially high values in the turbid area. This indicated that light attenuation was a key factor limiting phytoplankton blooms in turbid river estuaries.Plain Language Summary In estuaries and coastal waters, the aquatic environment is affected by both riverine nutrient input and water properties such as turbidity. The associated river plume may play an essential role in controlling water properties, thus influencing the aquatic environment such as the algal blooms. In the current study, a well-validated hydrodynamic-sediment-ecosystem model was used to simulate phytoplankton blooms and the dynamic link with the Changjiang River plume. The results showed that the surface suspended sediment front was of vital importance in determining the shoreward boundary of the phytoplankton bloom area. Light attenuation due to high turbidity became a major factor limiting phytoplankton blooms in turbid nearshore waters. In environments with a strong tidal influence, the surface suspended sediment front was closely related to the bottom river plume front, which gave rise to differences in water stabilization and thus resulted in turbid conditions on either side. The results of this study provided a good reference for understanding the phytoplankton distribution characteristics in estuaries with high turbidity.

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Section: Resultsmentioning

confidence: 97%

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

Wang

Lin

et al. 2019

JGR Oceans

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“…This summer Kuroshio subsurface branch was confirmed by field observations and tracer experiments and was named the Nearshore Kuroshio Branch Current (Yang et al, , ). Hydrographic observations of δ 18 O suggested that the KSSW off the northeast of Taiwan could reach as far north as 28°N off the Zhejiang coast via the bottom layer during March 2013 (Lian et al, ). The observed NO 3 − , δ 15 N‐NO 3 − , and δ 18 O indicated that KSSW could extend to the Zhejiang coastal area, after the intrusion onto the ECS northeast of Taiwan from May to June 2014 (Wang et al, ).…”

Section: Introductionmentioning

confidence: 99%

Key Dynamical Factors Driving the Kuroshio Subsurface Water to Reach the Zhejiang Coastal Area

Yang

Benthuysen

et al. 2018

JGR Oceans

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Observations indicate a seasonal variation of the Kuroshio subsurface water (KSSW) intrusion into the coastal region off the Zhejiang Province of China. The observed temperature and salinity distributions suggest a stronger intrusion in June and weaker intrusion in December. A hydrodynamic model well reproduces the seasonal variation of temperature and salinity characteristics and the current structure over the continental shelf. A passive tracer in the subsurface layer is used to investigate the movement of the KSSW. Tracer experiments confirm the seasonal variation of the KSSW intrusion, showing that the intrusion is stronger in summer and weaker in autumn and winter. Moreover, tracer concentrations suggest that in general it takes at least 1.5 months for the KSSW from east of Taiwan to reach the Zhejiang coastal area. Analyses of the momentum balances indicate that the KSSW's northward movement is regulated by the geostrophic current, while the shoreward intrusion results from the bottom Ekman effect. The seasonal changes in pressure gradients and vertical eddy viscosities contribute to the KSSW intrusion into the Zhejiang coastal area in June rather than in December. Sensitivity experiments show that the seasonal variation of the KSSW intrusion is mainly induced by the different wind stresses in summer and winter. The stronger southerly monsoon, the weaker and warmer Taiwan Warm Current, and the stronger and colder Kuroshio Current are favorable to the KSSW intrusion.

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“…In the offshore area northeast of Taiwan, the KSSW contribution can be over 80%, i.e., the water was basically equal to the source water. From northeast of Taiwan to the nearshore area, the KSSW contribution gradually decreased, which suggests that the KSSW mainly intrudes onto the ECS shelf from northeast of Taiwan (Hsueh et al, ; Lian et al, ; Liu et al, ; Tang et al, ; Yang et al, ). Furthermore, another high KSSW contribution core was observed at the offshore area of transect DH4 (∼28.5°N), and the KSSW contribution also gradually decreased shoreward.…”

Section: Resultsmentioning

confidence: 99%

Water Mass Analysis of the East China Sea and Interannual Variation of Kuroshio Subsurface Water Intrusion Through an Optimum Multiparameter Method

et al. 2018

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The Optimum Multiparameter (OMP) method was used to determine the relative contribution of water masses in the East China Sea (ECS) based on their measured temperature, salinity, and dissolved inorganic iodine species (DIIS, iodate and iodide) from recent oceanographic cruises in June 2014, 2015, and 2016. DIIS (as quasi‐conservative parameters) were added first into the OMP analysis, which enabled us to quantitatively estimate the water composition in the extremely dynamic and productive ECS. The OMP results indicate that seawater in the ECS mainly consisted of Changjiang Diluted Water (CDW), Taiwan Strait Warm Water (TSWW), Kuroshio Surface Water (KSW), and Kuroshio Subsurface Water (KSSW). In June 2014, 2015, and 2016, the KSSW dominated in the deep water, intruded into the ECS shelf from the northeast of Taiwan and bifurcated into a nearshore branch and offshore branch. The nearshore branch could reach north of 29°N off the Zhejiang coast. When comparing the KSSW intrusion in June 2014, 2015, and 2016, the average KSSW contribution of the bottom KSSW area in June 2016 (78.9%) was greater than in the previous 2 years (67.9% and 64.5%). In the northern transects (north of 28°N), the KSSW intrusion in June 2016 also contained the greatest average KSSW contribution and the maximum coverage area. Thus, the KSSW intrusion was strongest in June 2016 and may be comparable in June 2014 and 2015. This interannual variability of the KSSW intrusion is likely related to the El Niño‐Southern Oscillation (ENSO) rather than the Pacific Decadal Oscillation (PDO).

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Kuroshio subsurface water feeds the wintertime Taiwan Warm Current on the inner East China Sea shelf

Cited by 95 publications

References 65 publications

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

Phytoplankton Blooms off a High Turbidity Estuary: A Case Study in the Changjiang River Estuary

Key Dynamical Factors Driving the Kuroshio Subsurface Water to Reach the Zhejiang Coastal Area

Water Mass Analysis of the East China Sea and Interannual Variation of Kuroshio Subsurface Water Intrusion Through an Optimum Multiparameter Method

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