On the variability in the vertical structure of the Delaware coastal current

Previous studies have concluded that a distinctive feature of the buoyancy-driven Delaware coastal current lies in the fact that the coastal current extends to the bottom and flows next to the heavier shelf water rather than on top of it. The present study examines two sets of observations conducted in 1990 and 1992. The 1990 observations are consistent with previous findings, but the 1992 survey shows that the Delaware coastal current forms a clear surface layer on top of the shelf water. The wind does not provide an adequate explanation for the discrepancy between the two surveys, as downwelling favorable winds were present during both periods. The differences in the river discharge also appear inadequate in explaining the variability observed. The data suggest that the variation in the tidal mixing characteristics associated with the spring-neap modulation may contribute to the observed differences between the two cruises.