.
140
Tla: L5…” Resource
is only a few feet and in enclosed areas such as the Black Sea it is
reduced to nothing more than three to four inches. In contrast to
;;
this, the tidal range in the S evern Estuary in western England is over
‘
forty feet because the shape of the estuary funnels the tide into a
rapidly decreasing volume. In fact the only escape for the highest
spring tide is by pushing up the river—a wall—like front of surf,
‘
known as a bore, advances inland as far as Gloucester. The large
tidal range on the west coast is also due in part to the Earth’s
rotation which inuences all horizontal movements.
,
Any mass of water, whether in a bathtub or an ocean basin, has its
_
own
at whiCh‘Waves created by some disturbances
such as storms will run
and forth; they resonate;The period
of the North Sea from thendr—th—wèst direction, for eXample, is 35 to
40 hours. The elfectis particularly noticeable in lakes—the period of
Lake Eric is 14 hours. This kind of uctuation is called a seiche
"
after the French—SwiSs name for the rise and fall noticed on the
banks of Lake Geneva which has a period of râ— hours. Seiches have
«
nothing to do with astronomical tides, although —ocCasionally Seiches
can have a similar period, as in the Bay of F undy, thus enhancing
the tidal range. When such eXtra—high tides occur, they are known
Ï
as resonance tides. Therefotè‘seiches can be yet another complica—
tion tothe study of tides.
_
;
Obviously, untangling all the components which make up the
5
tide as recorded by tidal gauges and similar instruments is not easy.
A marigram—tlæ recOrd of the dde—is not a smooth line tracing
the rise and fall of the water but has numerous little uctuations.
Working fr0mthe observed tide, the :scientist—can, using a technique
'
called harmonic analysis, separate the various ‘Simple waves’
have
produce this complexrecording; With thiskind
;
of information and accurate details of planetary m0Vements, a model
or analogue machine can -:be built to …«comput‘e future
«this
way the-tide tables so
modern ports, as well
‘
holiday resorts, can be worked out a year or.soin advance.
:Cleay, the more tidal components allowed for in the machine—, the
more accurate the predictions, One tide—predicting machine5atthe
Institute of Coastal Oceanographyand Tides, Liverpool, can allow
:…for over …:forty different
such machines the 1tidës
the year at any one placé ÏëanbeWorked out‘within
Since the *tides are-«astrdr10micalin brigin, and other inuences
,
such as“»the” shape of
coast and the depth of the ‘îwater
n0t
-
140
Tla: L5…” Resource
is only a few feet and in enclosed areas such as the Black Sea it is
reduced to nothing more than three to four inches. In contrast to
;;
this, the tidal range in the S evern Estuary in western England is over
‘
forty feet because the shape of the estuary funnels the tide into a
rapidly decreasing volume. In fact the only escape for the highest
spring tide is by pushing up the river—a wall—like front of surf,
‘
known as a bore, advances inland as far as Gloucester. The large
tidal range on the west coast is also due in part to the Earth’s
rotation which inuences all horizontal movements.
,
Any mass of water, whether in a bathtub or an ocean basin, has its
_
own
at whiCh‘Waves created by some disturbances
such as storms will run
and forth; they resonate;The period
of the North Sea from thendr—th—wèst direction, for eXample, is 35 to
40 hours. The elfectis particularly noticeable in lakes—the period of
Lake Eric is 14 hours. This kind of uctuation is called a seiche
"
after the French—SwiSs name for the rise and fall noticed on the
banks of Lake Geneva which has a period of râ— hours. Seiches have
«
nothing to do with astronomical tides, although —ocCasionally Seiches
can have a similar period, as in the Bay of F undy, thus enhancing
the tidal range. When such eXtra—high tides occur, they are known
Ï
as resonance tides. Therefotè‘seiches can be yet another complica—
tion tothe study of tides.
_
;
Obviously, untangling all the components which make up the
5
tide as recorded by tidal gauges and similar instruments is not easy.
A marigram—tlæ recOrd of the dde—is not a smooth line tracing
the rise and fall of the water but has numerous little uctuations.
Working fr0mthe observed tide, the :scientist—can, using a technique
'
called harmonic analysis, separate the various ‘Simple waves’
have
produce this complexrecording; With thiskind
;
of information and accurate details of planetary m0Vements, a model
or analogue machine can -:be built to …«comput‘e future
«this
way the-tide tables so
modern ports, as well
‘
holiday resorts, can be worked out a year or.soin advance.
:Cleay, the more tidal components allowed for in the machine—, the
more accurate the predictions, One tide—predicting machine5atthe
Institute of Coastal Oceanographyand Tides, Liverpool, can allow
:…for over …:forty different
such machines the 1tidës
the year at any one placé ÏëanbeWorked out‘within
Since the *tides are-«astrdr10micalin brigin, and other inuences
,
such as“»the” shape of
coast and the depth of the ‘îwater
n0t
-