. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography VELOCITIES AT HW 777777777777/7777777 16 8 0 3 16 Cl^/SEC DISTRIBUTION OF VELOCITY COMPONENT ABOVE BOTTOM TRAJECTORY OF A WATER PARTICLE FIGURE 6. Typical tidal currents on a continental shelf where bottom stress forces the currents to zero speed at the bottom. From Fleming and Revelle (1939, p. 130); after Sverdrup (1927). With turbulent stresses, a more realistic profile of u is shown in Fig. 6, in which u decreases within the bottom b
. Collected reprints / Atlantic Oceanographic and Meteorological Laboratories [and] Pacific Oceanographic Laboratories. Oceanography VELOCITIES AT HW 777777777777/7777777 16 8 0 3 16 Cl^/SEC DISTRIBUTION OF VELOCITY COMPONENT ABOVE BOTTOM TRAJECTORY OF A WATER PARTICLE FIGURE 6. Typical tidal currents on a continental shelf where bottom stress forces the currents to zero speed at the bottom. From Fleming and Revelle (1939, p. 130); after Sverdrup (1927). With turbulent stresses, a more realistic profile of u is shown in Fig. 6, in which u decreases within the bottom boundary layer to essentially zero at the water-sediment interface. Since the tide propagates down the channel, it is a progressive tide. In this case, the maximum horizontal currents occur at higrrwater and low water where the current is in the direction and opposite to the direction of propagation, respectively. As the sea level passes through mean sea level, t; = 0, the current is momen- tarily zero. As a water parcel moves in the channel, its position X is the integral in time of the horizontal velocity: X u dt + A'0 (5) where A'0 is the position of the parcel at the initial time / = 0. Using (4), the horizontal displacement of the parcel is given by ^W'^M'-t)] + A'0 (6) Water subject to the tidal motion oscillates about an average position A'n with an amplitude equal to half the total excursion. For a semidaily tide (7" = hours) and a tidal range 2a = 1 m, the excursion for open sea depths (h = 4000 m) is km, whereas for shelf depths {h = 100 m) it is km. In (6), tidal currents would produce no net displace- ment of water or suspended particles. That is, if a water parcel were tagged using dye and observed throughout a tidal cycle, the parcel would return to the same location at the end of each tidal cycle. STANDING TIDES In bays and many estuaries, the incident progressive tide is reflected. The tide in this region is the combina- tion of the incident a
Size: 2371px × 1054px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, bookcollectionamericana, bookleafnumber226
