This paper presents observations of a dynamic minifilament an summariz
es the findings of three microstructure surveys across and within the
meandering current structures of the Coastal Transition Zone (CTZ). An
actively turbulent minifilament is discussed and possible consequence
s of the small-scale processes with regard to frontal dynamics are exa
mined. Four different frontal structures were observed as part of the
CTZ microstructtue program, two resembling meanders and two characteri
zed as filaments. Microstructure measurements included continuous rapi
d sampling vertical profiler (RSVP) (Caldwell et al., 1985) and acoust
ic Doppler current profiles (ADCP) profiling along meridional lines bi
secting the frontal features. Common features of the two meanders obse
rved in 1986: (Moum et al., 1988) and 1987: (Dewey and Moum, 1990) inc
lude offshore and onshore flow patterns (consistent with meridional se
ctions through meanders), rapid temporal evolution of the frontal stru
ctures between consecutive (10-24 hour) transects, no elevated turbule
nt activity below the pycnocline, despite the enhanced current shears
(quiescent core within central region where pycnocline is near surface
), and approximate geostrophy of the dominant currents at scales > 10
km. A large filament, or jetlike feature observed in 1988 (Dewey et al
., 1991) was characterized by off-shore geostrophic flow, no enhanced
turbulent activity, and significant asymmetry in the temperature, sali
nity and current fields, with stronger vorticity on the south (upwelle
d) side of the velocity maximum. An actively turbulent minifilament wa
s also observed in 1988, and exhibited some characteristics not common
to the larger meanders or filaments. A strongly divergent velocity si
gnature was confined to the near-surface layer (< 60 m), with a cool,
uplifted core, possibly a result of localized upwelling and subsurface
turbulent mixing. Below the surface mixed layer, elevated turbulent d
issipation rates were coincident with regions of high shear and corres
pondingly low Ri. However, the buoyancy flux from turbulent mixing was
estimated to be too low to have formed the cool surface signature of
the minifilament. The estimated Rossby number (R(o) = 1.3) for the min
ifilament suggests that significant departures from geostrophy are lik
ely. However, due to the limited temporal and zonal resolution of the
minifilament, no definitive ageostrophic analysis can be performed. Co
rresponding satellite images indicate that the observed structure, alt
hough narrow (10 km), may be as long as 100 km, be evolving over perio
ds of days, and a common submesoscale feature in the swirling patterns
revealed by advenced very hi resolution radiometer (AVHRR).