Geology Reference
In-Depth Information
Fig. 18.6
The “tidal amplifi cation window” (Sztanó and de
Boer
1995
) includes a number of variables (but does not
necessarily need to simultaneously honor all of these) such as
favourable depth and length for resonant amplifi cation, and
depth and width for the development of (an) amphidromic
point(s) (
Pugh 1996
; see also Chap. 13), and funnelling (cf. Bay
of Fundy). Basin-scale tidal amplifi cation thus may happen
during specifi c phases of (i) overall basin development as well
as (ii) relative sea-level cycles during one phase of basin
development during which the necessary requirements for
resonance are met. (
a
) The average depth of a basin determines
the celerity and the length of the propagating tidal wave. For
resonant amplifi cation the critical basin length should be an odd
multiple of the quarter of the tidal wave length. The
solid line
indicates the relation between the average water depth and the
length of the basin for one times the quarter of the tidal wave
length. The two successively steeper
dashed lines
indicate the
same relationship for three and fi ve times (the two following odd
multiples) the quarter of the tidal wave length respectively.
(
b
) The Rossby deformation radius of the Kelvin wave
describes how wide a basin should be for the development of an
amphidromic system. (
c
) The natural period of oscillation of
basins of different length depends on water depth. Cross-points
of the line of the M2 tide (12.42 h) with the hyperbolical curved
oscillation period time line for different basin lengths indicate
basin length and depth required for conditions near resonance of
the semidiurnal tide (modifi ed after Sztanó and de Boer (
1995
)
and based on Pugh (
1987, 1996
) )
