Buoyancy forced interaction between estuary and inner shelf: observation

In May and June of 1990 we explored the hydrographic variability of the Delaware Estuary and the adjacent inner shelf with shipboard instruments. We found significant three-dimensional density variability both within the estuary and on the shelf. We found weak vertical stratification but strong transverse variability within the estuary, with denser water concentrating in the center of the estuary and two branches of lighter water near both shores. On the shelf, the buoyant estuarine water forms a southward flowing coastal current in the direction of Kelvin wave phase propagation (downstream). ADCP observations and thermal wind calculations indicate a flow of 10–20 cm s⁻¹ downstream. Both the width of the coastal current and the magnitude of horizontal density gradients undergo substantial variations along the shelf.