Jf. Lynch et al., ACOUSTIC MEASUREMENTS OF THE SPATIAL AND TEMPORAL STRUCTURE OF THE NEAR-BOTTOM BOUNDARY-LAYER IN THE 1990-1991 STRESS EXPERIMENT, Continental shelf research, 17(10), 1997, pp. 1271-1295
As part of the 1990-1991 Sediment TRansport Events on Shelves and Slop
es (STRESS) experiment, a 5 MHz Acoustic BackScatter System (ABSS) was
deployed in 90 m of water to measure vertical profiles of near-bottom
suspended sediment concentration. By looking at the vertical profile
of concentration from 0 to 50 cm above bottom (cmab) with 1 cm vertica
l resolution, the ABSS was able to examine the detailed structure of t
he bottom boundary layer created by combined wave and current stresses
. The acoustic profiles clearly showed the wave-current boundary layer
, which extends to (order) 10 cmab. The profiles also showed evidence
of an ''intermediate'' boundary layer, also influenced by combined wav
e and current stresses, just above the wave-current boundary layer. Th
is paper examines the boundary-layer structure by comparing acoustic d
ata obtained by the authors to a I-D eddy viscosity model formulation.
Specifically, these data are compared to a simple extension of the Gr
ant-Glenn-Madsen model formulation. Also of interest is the appearance
of apparently 3-D ''advective plume'' structures in these data. This
is an interesting feature in a site which was initially chosen to be a
good example of (temporally averaged) I-D bottom boundary-layer dynam
ics. Computer modeling and sector-scanning sonar images are presented
to justify the plausibility of observing 3-D structure at the STRESS s
ite. (C) 1997 Elsevier Science Ltd.