In October, 1986 the surface waters adjacent to the Gulf Stream front
were surveyed with an undulating profiler to describe the finescale st
ructure of the mixed layer. The profiler was a Seasoar equipped with a
CTD and fluorometer. The survey first defined the structure of a cycl
onic eddy which resembled frontal eddies of the South Atlantic Bight i
n sea surface temperature imagery. The Seasoar transects revealed, how
ever, that the cyclonic eddy lacked a cold dome typically seen in fron
tal eddies. Farther downstream the Seasoar defined the structure of st
reamers of Gulf Stream and Shelf water wrapped about the southern edge
of a warm-core ring. The streamers had lateral and along-axis dimensi
ons on the order of approximate to 10 km and 100 km, respectively, and
were bordered by narrow intrusive features. The temporal history of t
he streamers was described from SST imagery, and the surface flow deri
ved from ship's drift vectors. CTD casts taken while following an isop
ycnal float provided a means to examine the structure of the intrusive
features. Interleaving was evident at the boundaries of the streamers
and intrusive features where high conductivity Cox numbers were conce
ntrated, suggesting elevated microstructure activity. The Turner angle
distribution, indicating either saltfingering or diffusive convection
, did not correlate well with the Cox number distribution. This is int
erpreted as evidence that lateral, rather than diapycnal, mixing was t
he process mediating the exchange of properties at the boundaries of c
ontrasting water types. In contrast to physical properties, the distri
bution of fluorescence showed relatively less structure in the surface
layer between the ring and Gulf Stream front. In the surface layers o
f the two streamers the pigment and bacterial biomass, and the diatom
species composition, were typical of Slope water communities. We hypot
hesize that small-scale mixing processes concentrated at the boundarie
s of the streamers were the mechanism by which Slope water plankton we
re seeded into streamers of different hydrographic origins. Presumably
, high netplankton growth rates allowed the Slope water species to dom
inate the communities in the streamers.