. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 172 SUBSTRATE RESPONSE TO HYDRAULIC PROCESS A\ 111 UMIN.'.TlON DIRECTION 'ERO RANGE °-^â -*â PRO' IE 0. SEA FLOOR ^^R DE BENEATH The Ship pL \ I VID UNES OF ECHOES 2 FROM SIDE LOBES NEAR EDGE OF MA. DISTANT EDGE OF MAIN BEAM FIGURE 13. (A) Sidescan sonar. (B) The resulting record. A, Bottom of seafloor; B, turbulence in water column due to ship's wake; C, zigzag pattern is due to refraction of sound in density- stratified water; D, main lobe (see a
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography 172 SUBSTRATE RESPONSE TO HYDRAULIC PROCESS A\ 111 UMIN.'.TlON DIRECTION 'ERO RANGE °-^â -*â PRO' IE 0. SEA FLOOR ^^R DE BENEATH The Ship pL \ I VID UNES OF ECHOES 2 FROM SIDE LOBES NEAR EDGE OF MA. DISTANT EDGE OF MAIN BEAM FIGURE 13. (A) Sidescan sonar. (B) The resulting record. A, Bottom of seafloor; B, turbulence in water column due to ship's wake; C, zigzag pattern is due to refraction of sound in density- stratified water; D, main lobe (see above); E, side lobe. From Belderson et al. (2972). scale cells have wavelengths much greater than 1 \D and are oriented to the right of geostrophic flow. They occur at much lower Reynolds numbers. Helical flow structure may occur in the upper Ekman layer where its wind-driven stirring creates the mixed layer above the thermocline (Faller, 1971), or may occur in the lower layer (Faller, 1963). In surface helical flow the downwelling zones that collect the high-velocity wind-driven surface water are more sharply defined than the upwelling zones (Langmuir, 1925). In bottom helical flow, downwelling zones deliver higher velocity water to the seafloor, and may also be more sharply defined than the upwelling zones. During intense flows, when strati- fication breaks down and the layers partly or completely overlap, a compound top-to-bottom helical flow struc- ture might be expected. Observational and theoretical studies required to link this scheme to the observed shelf sand ribbon patterns have not been undertaken; however, there are obvious points of compatibility. The ribbons tend to be parallel, or oriented at a small angle to the regional trend of shelf contours, and presumably to the mean geostrophic flow direction. The greater intensity of downwelling zones would explain the dissimilar width of ribbons and inter- vening erosional windows. The Reynolds numbers re- quired are
Size: 2465px × 1014px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, bookcollectionamericana, bookleafnumber597
