On the Hydrographic Distribution in the Source Region of the Delaware Coastal Current

• Published in: Estuaries 1999-06, Vol.22 (2), p.194-205
• Main Author: Wong, Kuo-Chuin
• Format: Article
• Language: English
• Subjects: Buoyancy; Coastal currents; Coastal water; Coasts; Continental shelves; Diurnal variations; Earth, ocean, space; Estuaries; Exact sciences and technology; External geophysics; Floods; Frontal boundaries; Hydrology; Marine; Ocean currents; Other topics; Physics of the oceans; Plumes; Salinity; Shoals; Tides; USA, Delaware; Water column
• ISSN: 0160-8347; 1559-2723; 1559-2758; 1559-2731
• DOI: 10.2307/1352976

The buoyant discharge from Delaware Bay forms two separate branches of residual outflow near the bay mouth, one along each shore. Upon exiting the bay, the branch along the Delaware shore turns right to form the southward flowing Delaware coastal current along the inner continental shelf off the Delaware, Maryland, and Virginia coasts. CTD and thermosalinograph data collected at the mouth of Delaware Bay over two semidiurnal tidal cycles are used to examine the hydrographic distribution at the source region of the Delaware coastal current. In this region the buoyant source water of the coastal current is largely detached from the shoreline and confined to the top 15 m of the water column over much of the tidal cycles. The core of the coastal current's source water, as defined by the point of salinity minimum, is located over the deep channel well offshore of the Delaware coast. The separation between this buoyant water and the more saline waters right along the Delaware coast and that in the central part of the bay mouth are marked by regions of high horizontal salinity gradients. The horizontal salinity gradients around the inshore and offshore boundaries of the source water of the coastal current are intensified during the flood tide, and clearly defined fronts (with a change of 3‰ over a distance of 150 m) are present at the offshore boundary near the end of the flood tide. The structure of the mean flow and the distribution of the brackish coastal current on the inner continental shelf contribute to the persistence of stratification in the source region off the Delaware shore throughout the ebb and flood tides. In contrast, the ebb-induced stratification in the region off the New Jersey shore is quickly destroyed with the onset of the flood current.