Eddies and intrusion of Gulf Stream water are frequently observed 
offshore of Oregon Inlet, probably as a result of (1) lateral move- 
ment of the Gulf Stream or (2) propagation of Gulf Stream meanders 
downstream of Cape Hatteras. The warm water is limited to the surface 
layer (100 meters), unlike observed large-scale Gulf Stream eddies, 
which may extend considerably deeper. Sea surface temperature is 
comparable to or slightly less than Gulf Stream temperatures with 
temperature change and gradients across the front generally slightly 
less than those across the northern edge. A well-defined northern 
edge may not be apparent at the surface in the presence of a warm 
area or eddy. Temperature inversions appear to be common immediately 
below the warm surface water. No information is available as to 
currents in eddies, but anticyclonic circulation is inferred from 
thermohaline relationships. 
The larger, semipermanent warm area in the northeastern quadrant 
of the study area is characterized by maximum SST of 15° to 17°C in 
winter and near-Gulf Stream temperature in summer. Temperature change 
across the front varies from 2° to 5°C with a gradient of 1°C/km or 
less. Thermohaline relationships indicate a Gulf Stream origin. 
Shelf Water in the western part of the study area may be expected 
to have an SST ranging from a minimum of about 5°C in winter to a 
maximum of greater than 27°C in summer. A frontal zone may be expected 
to separate the Shelf Water from offshore Slope Water in winter with 
temperature change and gradient across the front on the order of 5°C 
and 1°C/km, respectively. A temperature inversion impinging upon the 
Continental Slope (Cresswell, 1967; Fisher, 1969) marks the boundary 
between Shelf Water and Slope Water during summer and autumn. Entrain- 
ment of Shelf Water by the Gulf Stream occurs intermittently at a rate 
of about 1 x 10%m /sec., forming a cold filament along the northern 
edge. Shelf currents are generally southwesterly at speeds less than 
20 cm/sec. Bumpus (1969) shows that current reversals may occur after 
periods of low rainfall. 
Slope Water seaward of the Continental Shelf and inshore of the 
Gulf Stream is modified considerably through introduction of Gulf Stream 
water (eddies) and Shelf Water (offshore movement of temperature in- 
versions). SST is comparable to Shelf Water during summer and is sever- 
al degrees warmer than Shelf Water during winter. Pools of water of 
Gulf Stream origin frequently appear both as transient (eddies) and 
semipermanent (warm areas) features with corresponding SST. Thermal 
structure of Shelf Water is greatly complicated by intrusion of water 
from other sources but generally may be characterized by neutral or 
positive temperature gradients to depths exceeding 200 meters in winter 
and by strong negative gradients underlain by well-defined temperature 
inversions during summer and autumn. 
