Journal cover Journal topic
Ocean Science An interactive open-access journal of the European Geosciences Union
Ocean Sci., 13, 105-122, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
10 Feb 2017
Synoptic fluctuation of the Taiwan Warm Current in winter on the East China Sea shelf
Jiliang Xuan1, Daji Huang1,2, Thomas Pohlmann3, Jian Su3, Bernhard Mayer3, Ruibin Ding2,1, and Feng Zhou1,2 1State Key Laboratory of Satellite Ocean Environment Dynamics, Second Institute of Oceanography, State Oceanic Administration, Hangzhou, China
2Ocean College, Zhejiang University, Zhoushan, China
3Institute of Oceanography, University of Hamburg, Hamburg, Germany
Abstract. The seasonal mean and synoptic fluctuation of the wintertime Taiwan Warm Current (TWC) were investigated using a well-validated finite volume community ocean model. The spatial distribution and dynamics of the synoptic fluctuation were highlighted. The seasonal mean of the wintertime TWC has two branches: an inshore branch between the 30 and 100 m isobaths and an offshore branch between the 100 and 200 m isobaths. The Coriolis term is much larger than the inertia term and is almost balanced by the pressure gradient term in both branches, indicating geostrophic balance of the mean current. Two areas with significant fluctuations of the TWC were identified during wintertime. One of the areas is located to the north of Taiwan with velocities varying in the cross-shore direction. These significant cross-shore fluctuations are driven by barotropic pressure gradients associated with the intrusion of the Taiwan Strait Current (TSC). When a strong TSC intrudes to the north of Taiwan, the isobaric slope tilts downward from south to north, leading to a cross-shore current from the coastal area to the offshore area. When the TSC intrusion is weak, the cross-shore current to the north of Taiwan is directed from offshore to inshore. The other area of significant fluctuation is located in the inshore area between the 30 and 100 m isobaths. The fluctuations are generally strong both in the alongshore and cross-shore directions, in particular at the latitudes 26.5 and 28° N. Wind affects the synoptic fluctuation through episodic events. When the northeasterly monsoon prevails, the southwestward Zhe-Min coastal current dominates the inshore area associated with a deepening of the mixed layer. When the winter monsoon is weakened or the southwesterly wind prevails, the northeastward TWC dominates in the inshore area.

Citation: Xuan, J., Huang, D., Pohlmann, T., Su, J., Mayer, B., Ding, R., and Zhou, F.: Synoptic fluctuation of the Taiwan Warm Current in winter on the East China Sea shelf, Ocean Sci., 13, 105-122,, 2017.
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Short summary
Research on the summer TWC has been conducted previously; however, the spatial structure and temporal variation of the winter TWC are less known due to its weak mean velocity. Therefore, FVCOM was used to evaluate the spatial patterns of TWC synoptic fluctuations. We observed that the TWC fluctuations appear mainly to the north of Taiwan and in the inshore area. Our results will be useful in the dynamical understanding of the winter TWC and its impact on cross-shore transport.
Research on the summer TWC has been conducted previously; however, the spatial structure and...