Tabic 5. — Cold cell crossings in the Cape Hatterus area by 

 SOOP vessels in 1975. 



Some ot these SOOP crossings show the winter water 

 that eventually forms the cold cell, some show calving, 

 and some show the cold cell extending off the continental 

 shelf. 



In February, the Santa Cruz (App. Fig. 28) crossed 

 through winter water of <5°C near the mouth of 

 Chesapeake Bay. This crossing was important because it 

 shows the coldest water crossed by SOOP vessels in the 

 Cape Hatteras area and implies that the cold cell which 

 was formed from this water could not be any colder than 

 that temperature section shows. 



In Ma\ , the Mormac Argo (App. Fig. 32) crossed over a 

 "double bubble" of the cold cell. The more inshore bub- 

 ble had temperatures lower (<7°C) than that of the off- 

 shore bubble (<8°C). Because the transect was nearly 

 parallel to shore, the "double bubble" could be an ar- 

 tifact of the contouring. Lobes have been detected in the 

 shape of the cold cell, and if a transect crossed through 

 two lobes, a "double bubble"-like feature would be in- 

 dicated. Two transects in June (App. Figs. 33 and 34), 

 both obtained by the USCGC Chase, showed the cold 

 cell well developed with strong stratification above and 

 offshore. The 15 June (App. Fig. 33) transect shows a 

 parcel of cooler water that has "calved" off the main cold 

 cell structure up on the shelf. 



Just one day later, on 16 June (App. Fig. 34), almost 

 the same transect as on 15 June was repeated and showed 

 the parcel of cooler water that had "calved" off earlier 

 almost totallv mixed away. 



The close proximity of the north wall of the Gulf 

 Stream to the cold cell and the cold cell parcels war- 

 ranted a closer look at the satellite imagery in that area 

 for that time period. Examination of the Experimental 

 Ocean Frontal Analysis Charts produced by the Naval 

 Oceanographic Office from 28 May through 16 June of 

 1975 showed a maximum movement of the north wall 30 

 n.mi. in 12 days or about 2.5 n. mi. /day (4.6 km/day), well 

 within past observations of 10 n.mi. /day in the same 

 area. At the same time the Experimental Ocean Frontal 

 Analysis Charts showed a shoreward movement between 

 28 May and 4 June then seaward movement between 9 

 and 16 June of the north wall of the Gulf Stream. 



As discussed earlier in the Gulf Stream section, the 

 translational velocities of the north wall of the Gulf 

 Stream indicated the possibility that shoreward incur- 

 sions of the Gulf Stream are large enough in the Cape 

 Hatteras area to act upon the cold cell features on the 

 shelf and possibly pull out parcels of the cold cell. 



In summary, we feel that the section obtained on 15 

 June shows the aftereffects of the shoreward, then sea- 

 ward, movement of the north wall, where the north wall 

 has acted as the forcing agent in breaking a piece of the 

 cold cell off from the main body and then dragging it 

 seaward as the north wall again moves offshore. 



The transects collected in September and October 

 (App. Figs. 36, 39, and 42) show how the cold cell has 

 eroded away throughout the summer. The lowest 

 temperatures in the cold cell were only slightly <9°C in 

 September and slightly <11°C in October. 



Shelf water-slope water front. — XBT transects were 

 made across the shelf water-slope water front (SSF) in 

 the Cape Hatteras area on 12 occasions during 1975 (see 

 Table 6 and App. Figs. 27, 28, 30, 34, 36, 37, 41, 42, and 

 45). Determinations of frontal crossings were made on 

 the basis of subsurface temperature gradients shown on 

 the vertical sections with additional supporting evidence 

 being drawn from sea surface temperature and salinity 

 data. 



Table (J. 



-Self water-slope water front erossings in the Cape Hatteras 

 area by SOOP vessels in 1975. 



