Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 14 8 2010 10.5194/hess-14-1465-2010 http://www.hydrol-earth-syst-sci.net/14/1465/2010/ http://www.hydrol-earth-syst-sci.net/14/1465/2010/hess-14-1465-2010.html http://www.hydrol-earth-syst-sci.net/14/1465/2010/hess-14-1465-2010.pdf 1465 1476 2010-08-05 Using flushing rate to investigate spring-neap and spatial variations of gravitational circulation and tidal exchanges in an estuary D. C. Shaha Y.-K. Cho ykcho@chonnam.ac.kr G.-H. Seo C.-S. Kim K. T. Jung Department of Oceanography, Chonnam National University, Gwangju 500–757, Korea Korea Ocean Research and Development Institute, Ansan 426–744, Korea Spring-neap and spatial variations of gravitational circulation and tidal exchanges in the Sumjin River Estuary (SRE) were investigated using the flushing rate. The flushing rate was calculated between multiple estuarine segments and the adjacent bay to examine the spatial variation of two exchanges. The strength of gravitational circulation and tidal exchanges modulated significantly between spring and neap tides, where stratification alternated between well-mixed and highly-stratified conditions over the spring-neap cycle. Tide-driven dispersive flux of salt dominated over gravitational circulation exchange near the mouth during spring tide due to the larger tidal amplitude that caused well-mixed conditions and rapid exchange. In contrast, the central and inner regimes were found to be partially stratified during spring tide due to the reduction in tidal amplitude where both gravitational circulation and tidal exchanges were important in transporting salt. The combined contributions of two fluxes were also found during neap tide along the SRE due to the significant reduction in vertical mixing that accompanied strong stratification. Gravitational circulation exchange almost entirely dominated in transporting salt at the upstream end during spring and neap tides. Bae, D. 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