Abstract
Wanquan River is a small river located in Hainan, a tropical island in China. As the third largest river in Hainan, the river plume plays an important role in the regional terrigenous mass transport, coastal circulation, and the coral reef’s ecosystem. Studies have shown that wind forcings significantly influence river plume dynamics. In this study, wind effects on the dispersal of the river plume and freshwater transport were examined numerically using a calibrated, unstructured, finite volume numerical model (FVCOM). Both wind direction and magnitude were determined to influence plume dispersal. Northeasterly (downwelling-favorable) winds drove freshwater down-shelf while southeasterly (onshore) winds drove water up-shelf (in the sense of Kelvin wave propagation), and were confined near the coast. Southwesterly (upwelling-favorable) and north-westerly (offshore) winds transport more freshwater offshore. The transport flux is decomposed into an advection, a vertical shear, and an oscillatory component. The advection flux dominates the freshwater transport in the coastal area and the vertical shear flux is dominant in the offshore area. For the upwelling-favorable wind, the freshwater transport becomes more controlled by the advection transport with an increase in wind stress, due to enhanced vertical mixing. The relative importance of wind forcing and buoyancy force was investigated. It was found that, when the Wedderburn number is larger than one, the plume was dominated by wind forcing, although the importance of wind varies in different parts of the plume. The water column stratification decreased as a whole under the prevailing southwesterly wind, with the exception of the up-shelf and offshore areas.
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Acknowledgements
This study is funded by the National Natural Science Foundation of China (Grant No. 40976052). This research is supported in part by Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase). The authors would like to acknowledge Mr. Mac Sisson of Virginia Institute of Marine Science for his help in editing the manuscript. We are also grateful for the three anonymous reviewers for helpful comments on the manuscript.
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Junpeng Zhao is a Ph.D candidate in Sun Yat-Sen University, Guangzhou, China. He received his Bachelor’s Degree at Henan University in 2009, and his Master’s Degree in physical oceanography in 2011 at Sun Yat-Sen University.
His major field of study is estuarine circulation, salt intrusion in estuaries, and river plume dynamics.
Wenping Gong is a professor in the School of Marine Science, Sun Yat-Sen University, Guangzhou, China. He received his Bachelor’s Degree and Master’s Degree in natural geography in 1990 and 1993 at Nanjing University, respectively. He was awarded his Ph.D. degree in physical geography in 1997 at East China Normal University, Shanghai.
He worked in the Department of Civil Engineering, the University of Liverpool, from 2000–2001, followed by a position at the Virginia Institute of Marine Science, Virginia, USA from 2003–2008. His research interests are estuarine and coastal hydrodynamics, sediment dynamics, and water quality.
Jian Shen is a Professor of physical oceanography in Virginia Institute of Marine Science, Virginia, USA. He earned his Bachelor’s Degree from Shanghai Normal University, and his Master’s and Ph. D. degrees inform the College of William and Mary, Virginia, USA.
He worked as a visiting scientist in The Netherlands Institute for Sea Research, The Netherlands from 1986–1987, followed by a position as a Senior Environment Engineer at Tetra Tech, Inc. after he completed his Ph.D. studies. He then returned to the Virginia Institute of Marine Science for further academic research. His research interests include: estuarine circulation, inverse modeling of estuarine water quality, storm surge and inundation predictions; numerical model simulations of hydrodynamics and water quality in estuaries and coastal sea; and numerical modeling of watershed processes.
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Zhao, J., Gong, W. & Shen, J. The effect of wind on the dispersal of a tropical small river plume. Front. Earth Sci. 12, 170–190 (2018). https://doi.org/10.1007/s11707-016-0628-6
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DOI: https://doi.org/10.1007/s11707-016-0628-6