Using flushing rate to investigate spring-neap and spatial variations of gravitational circulation and tidal exchanges in an estuary

摘要

Spring-neap and spatial variations of gravitational circulation and tidalexchanges in the Sumjin River Estuary (SRE) were investigated using theflushing rate. The flushing rate was calculated between multiple estuarinesegments and the adjacent bay to examine the spatial variation of twoexchanges. The strength of gravitational circulation and tidal exchangesmodulated significantly between spring and neap tides, where stratificationalternated between well-mixed and highly-stratified conditions over thespring-neap cycle. Tide-driven dispersive flux of salt dominated overgravitational circulation exchange near the mouth during spring tide due tothe larger tidal amplitude that caused well-mixed conditions and rapidexchange. In contrast, the central and inner regimes were found to bepartially stratified during spring tide due to the reduction in tidalamplitude where both gravitational circulation and tidal exchanges wereimportant in transporting salt. The combined contributions of two fluxeswere also found during neap tide along the SRE due to the significantreduction in vertical mixing that accompanied strong stratification. Gravitationalcirculation exchange almost entirely dominated in transporting salt at theupstream end during spring and neap tides.