Abstract
Temperature and salinity data, obtained by two snapshot surveys during 19–20 May 2019 and 12–25 September 2019 across the East China Sea (ECS) shelf, revealed that the Kuroshio intrusion to the north of 28°N comprised the Nearshore Kuroshio Branch Current (NKBC) and the Offshore Kuroshio Branch Current (OKBC) at the bottom of the ECS during spring 2019, and that the NKBC was weak during autumn 2019. The Regional Ocean Model System was used to reproduce the distribution of water masses and the current structure over the continental shelf of the ECS during 2019. Analyses of the momentum balances indicated that the cross-shore range and the intensity of the NKBC were determined by the combination of the geostrophic flow and bottom Ekman current. In comparison with that in May 2019, a weakened shoreward bottom Ekman current and an increased offshoreward geostrophic flow caused the disappearance of cross-shore range of the NKBC in September 2019. Meanwhile, a diminished northeastward alongshore geostrophic flow in September 2019 also weakened the intensity of the NKBC. Sensitivity experiments indicated that a strong southwestward wind can push the western (eastern) boundary of the NKBC further offshoreward (shoreward) by increasing (decreasing) the offshore geostrophic flow (bottom Ekman current). A weak Taiwan Warm Current (TWC) can move the eastern boundary of the NKBC shoreward by decreasing the onshore bottom Ekman current. A weak Kuroshio Current (KC) can move the eastern boundary of the NKBC shoreward by increasing the offshoreward geostrophic flow. Furthermore, a strong (weak) southwestward wind, weak (strong) TWC, and strong (weak) KC can diminish (enhance) the intensity of the NKBC. Of the three factors, the wind plays the major role in influencing the NKBC.
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Data Availability Statement
The WOA13 and NCEP CFSv2 data is maintained and distributed by National Oceanic and Atmospheric Administration (NOAA) at http://www.nodc.noaa.gov. The HYCOM 3.1 data are available at https://www.hycom.org/. The bottom topography is extracted from the General Bathymetric Chart of the Oceans (1/120°) at https://www.gebco.net/data_and_products/gridded_bath-ymetry_data/.
References
Chen C T A, Wang S L. 1999. Carbon, alkalinity and nutrient budgets on the East China Sea continental shelf. Journal of Geophysical Research: Oceans, 104(C9): 20 675–20 686, https://doi.org/10.1029/1999JC900055.
Chen C T A. 1996. The Kuroshio intermediate water is the major source of nutrients on the East China Sea continental shelf. Oceanologica Acta, 19(5): 523–527.
Chen H W, Liu C T, Matsuno T, Ichikawa K, Fukudome K I, Yang Y, Doong D J, Tsai W L. 2016. Temporal variations of volume transport through the Taiwan Strait, as identified by three-year measurements. Continental Shelf Research, 114: 41–53.
Egbert G D, Erofeeva S Y. 2002. Efficient inverse Modeling of barotropic ocean tides. Journal of Atmospheric and Oceanic Technology, 19(2): 183–204, https://doi.org/10.1175/1520-0426(2002)019<0183:EIMOBO>2.0.CO;2.
Guo X Y, Hukuda H, Miyazawa Y, Yamagata T. 2003. A triply nested ocean model for simulating the Kuroshio — Roles of horizontal resolution on JEBAR. Journal of Physical Oceanography, 33(1): 146–169, https://doi.org/10.1175/1520-0485(2003)033<0146:ATNOMF>2.0.CO;2.
Guo X Y, Miyazawa Y, Yamagata T. 2006. The Kuroshio onshore intrusion along the shelf break of the East China Sea: the origin of the Tsushima Warm Current. Journal of Physical Oceanography, 36(12): 2 205–2 231, https://doi.org/10.1175/JPO2976.1.
Haidvogel D B, Arango H, Budgell W P, Cornuelle B D, Curchitser E, Di Lorenzo E, Fennel K, Geyer W R, Hermann A J, Lanerolle L, Levin J, McWilliams J C, Miller A J, Moore A M, Powell T M, Shchepetkin A F, Sherwood C R, Signell R P, Warner J C, Wilkin J. 2008. Ocean forecasting in terrain-following coordinates: formulation and skill assessment of the Regional Ocean Modeling System. Journal of Computational Physics, 227(7): 3595–3624, https://doi.org/10.1016/j.jcp.2007.06.016.
Hu F, Liu Y H, Xu Z H, Yin Y Q, Hou Y J. 2020. Bidirectional volume exchange between Kuroshio and East China Sea shelf water based on a whole-region passive-tracing method. Journal of Geophysical Research: Oceans, 125(5): e2019JC015528, https://doi.org/10.1029/2019JC015528.
Hu J Y, Wang X H. 2016. Progress on upwelling studies in the China seas. Reviews of Geophysics, 54(3): 653–673, https://doi.org/10.1002/2015RG000505.
Ichikawa H, Beardsley R C. 2002. The current system in the Yellow and East China Seas. Journal of Oceanography, 58(1): 77–92, https://doi.org/10.1023/A:1015876701363.
Isobe A. 2008. Recent advances in ocean-circulation research on the Yellow Sea and East China Sea shelves. Journal of Oceanography, 64(4): 569–584, https://doi.org/10.1007/s10872-008-0048-7.
Jacobs G A, Hur H B, Riedlinger S K. 2000. Yellow and East China Seas response to winds and currents. Journal of Geophysical Research: Oceans, 105(C9): 21 947–21 968, https://doi.org/10.1029/2000JC900093.
Kondo M. 1985. Oceanographic investigations of fishing grounds in the East China Sea and the Yellow Sea-I. Characteristics of the mean temperature and salinity distributions measured at 50 m and near the bottom. Bull. Seikai Reg. Fish Res. Lab., 62: 19–66.
Lee H J, Chao S Y. 2003. A climatological description of circulation in and around the East China Sea. Deep Sea Research Part II: Topical Studies in Oceanography, 50(6–7): 1 065–1 084, https://doi.org/10.1016/S0967-0645(03)00010-9.
Lee T N, Johns W E, Liu C T, Zhang D X, Zantopp R, Yang Y 2001. Mean transport and seasonal cycle of the Kuroshio east of Taiwan with comparison to the Florida current. Journal of Geophysical Research: Oceans, 106(C10): 22 143–22 158, https://doi.org/10.1029/2000JC000535.
Liu K K, Tang T Y, Gong G C, Chen L Y, Shiah F K. 2000. Cross-shelf and along-shelf nutrient fluxes derived from flow fields and chemical hydrography observed in the southern East China Sea off northern Taiwan. Continental Shelf Research, 20(4–5): 493–523, https://doi.org/10.1016/S0278-4343(99)00083-7.
Mellor G L, Yamada T. 1982. Development of a turbulence closure model for geophysical fluid problems. Reviews of Geophysics, 20(4): 851–875, https://doi.org/10.1029/RG020i004p00851.
Oey L Y, Hsin Y C, Wu C R. 2010. Why does the Kuroshio northeast of Taiwan shift shelfward in winter? Ocean Dynamics, 60(2): 413–426, https://doi.org/10.1007/s10236-009-0259-5.
Shchepetkin A F, McWilliams J C. 2005. The regional oceanic modeling system (ROMS): a split-explicit, free-surface, topography-following-coordinate oceanic model. Ocean Modelling, 9(4): 347–404, https://doi.org/10.1016/j.ocemod.2004.08.002.
Song Y H, Haidvogel D. 1994. A semi-implicit ocean circulation model using a generalized topography-following coordinate system. Journal of Computational Physics, 115(1): 228–244, https://doi.org/10.1006/jcph.1994.1189.
Wang J, Oey L Y. 2016. Seasonal exchanges of the Kuroshio and shelf waters and their impacts on the shelf currents of the East China Sea. Journal of Physical Oceanography, 46(5): 1 615–1 632, https://doi.org/10.1175/JPO-D-15-0183.1.
Wang W T, Yu Z M, Song X X, Wu Z X, Yuan Y Q, Zhou P, Cao X H. 2016. The effect of Kuroshio Current on nitrate dynamics in the southern East China Sea revealed by nitrate isotopic composition. Journal of Geophysical Research: Oceans, 121(9): 7 073–7 087, https://doi.org/10.1002/2016JC011882.
Wang Y H, Jan S, Wang D P. 2003. Transports and tidal current estimates in the Taiwan Strait from shipboard ADCP observations (1999–2001). Estuarine, Coastal and Shelf Science, 57(1–2): 193–199, https://doi.org/10.1016/S0272-7714(02)00344-X.
Xu L J, Yang D Z, Benthuysen J A, Yin B S. 2018. Key dynamical factors driving the Kuroshio subsurface water to reach the Zhejiang Coastal Area. Journal of Geophysical Research: Oceans, 123(12): 9 061–9 081, https://doi.org/10.1029/2018JC014219.
Yang D Z, Huang R X, Yin B S, Feng X R, Chen H Y, Qi J F, Xu L J, Shi Y L, Cui X, Gao G D, Benthuysen J A. 2018a. Topographic beta spiral and onshore intrusion of the Kuroshio current. Geophysical Research Letters, 45(1): 287–296, https://doi.org/10.1002/2017GL076614.
Yang D Z, Yin B S, Chai F, Feng X R, Xue H J, Gao G D, Yu F. 2018b. The onshore intrusion of Kuroshio subsurface water from February to July and a mechanism for the intrusion variation. Progress in Oceanography, 167: 97–115, https://doi.org/10.1016/j.pocean.2018.08.004.
Yang D Z, Yin B S, Liu Z L, Bai T, Qi J F, Chen H Y. 2012. Numerical study on the pattern and origins of Kuroshio branches in the bottom water of southern East China Sea in summer. Journal of Geophysical Research: Oceans, 117(C2): C02014, https://doi.org/10.1029/2011JC007528.
Yang D Z, Yin B S, Liu Z L, Feng X R. 2011. Numerical study of the ocean circulation on the East China Sea shelf and a Kuroshio bottom branch northeast of Taiwan in summer. Journal of Geophysical Research: Oceans, 116(C5): C05015, https://doi.org/10.1029/2010JC006777.
Yang D Z, Yin B S, Sun J C, Zhang Y. 2013. Numerical study on the origins and the forcing mechanism of the phosphate in upwelling areas off the coast of Zhejiang province, China in summer. Journal of Marine Systems, 123–124: 1–18, https://doi.org/10.1016/j.jmarsys.2013.04.002.
Zhou P, Song X X, Yuan Y Q, Cao X H, Wang W T, Chi L B, Yu Z M. 2018. Water mass analysis of the East China Sea and interannual variation of Kuroshio subsurface water intrusion through an optimum multiparameter method. Journal of Geophysical Research: Oceans, 123(5): 3 723–3 738, https://doi.org/10.1029/2018JC013882.
Zhou P, Song X X, Yuan Y Q, Wang W T, Cao X H, Yu Z M. 2017. Intrusion pattern of the Kuroshio subsurface water onto the East China Sea continental shelf traced by dissolved inorganic iodine species during the spring and autumn of 2014. Marine Chemistry, 196: 24–34, https://doi.org/10.1016/j.marchem.2017.07.006.
Acknowledgment
Data and samples were collected onboard of R/V Xiang Yang Hong 18 implementing the open research cruise NORC2019-02 supported by NSFC Shiptime Sharing Project (project number: 41749902). The study was also supported by the High Performance Computing Center at IOCAS.
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Supported by the National Natural Science Foundation of China (Nos. 41630967, 41776020)
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Yan, J., Hou, Y., Qi, P. et al. Numerical study of the cross-shore range and the intensity of the Nearshore Kuroshio Branch Current (NKBC). J. Ocean. Limnol. 40, 37–54 (2022). https://doi.org/10.1007/s00343-021-0291-y
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DOI: https://doi.org/10.1007/s00343-021-0291-y