from mixing of coastal and oceanic water, and (5) the transition 

 from coastal to oceanic water occurs in a narrow belt only 20 

 nautical miles (37 kilometers) wide off Chesapeake Bay. 



Hopkins and Burt (1951), discussing the vertical thermohaline 

 structure at the entrance to Chesapeake Bay, state that (1) a strong 

 negative temperature gradient is usually accompanied by a strong posi- 

 tive salinity gradient, (2) a positive temperature gradient must be 

 accompanied by a strong positive salinity gradient if vertical sta- 

 bility is to be maintained, and (3) absence of a temperature gradient 

 does not indicate the absence of a salinity gradient. 



Several exceptions to the thermohaline distribution as described 

 by Bigelow (1933) and Bigelow and Sears (1935) have been noted. Mil- 

 ler (1952) reported that the southerly flowing coastal current is 

 diverted eastward of Cape Henry as much as UO miles (74 km) by Chesa- 

 peake Bay discharge. The effect of the discharge is most prominent 

 southeast of the bay; salinity as low as 31°/oo has been observed 

 well offshore. This eastward flow is compensated by a westerly flow 

 at 36''U0*N. Howe (1962) reported that the seaward sweep of the cur- 

 rent is subject to sudden and irregular meanders. 



Ichiye (1966, 1967) reported the existence of a warm eddy about 

 100 kilometers in diameter approximately 150 kilometers northeast of 

 Cape Hatteras, A vertical section of the eddy showed a complex ther- 

 mohaline structure caused by entrainment of coastal water and by 

 intrusion of Gulf Stream water. The lifetime of the eddy was believed 

 to be several weeks. 



DATA COLLECTION 



Sea surface temperature (SST) was measured with an airborne radi- 

 ation thermometer (ART) aboard the ASWEPS aircraft. Three flights 

 were conducted during Phase I and one flight was made during Phase II, 

 The ART data have been corrected for environmental effects. Twenty- 

 five comparisons of SST recorded at intersections of the aircraft 

 track with the USNS GILLISS (T-AGOR-U) track showed an average dif- 

 ference of 0.1°C with a standard deviation of +0.2°C between ship and 

 aircraft observations taken during the same day. Data were rejected 

 where fog, precipitation, or low clouds obscured the surface. Navi- 

 gational accuracy is estimated to be within 5 kilometers. Small irregu- 

 larities in the isotherm pattern may result from errors in navigation, 

 measurement, data processing, and/or analysis. No corrections were 

 applied for tidal effects or diurnal heating. 



Vertical distribution of temperature and salinity was measured 

 to the bottom by the GILLISS using shipboard expendable bathythermo- 

 graphs (SXBT) and Nansen casts with bottles spaced at intervals of 

 5 meters. Twenty-three SXBT stations were taken during Phase I when 



