TIDE CUKVE 



tidal datum plane— ^S'ee chart datum, 

 tidal day — See lunar day. 



tidal delta — Sand bars or shoals formed in the 

 entrance of inlets by reversing tidal currents. 



(2) 



tidal difference — The difference ni time or height 

 of !x liigh or low water between a subordinate 

 station and a reference station. The differ- 

 ence is applied to the prediction at the reference 

 station to obtain the time or heiglit of the tide 

 at a subordinate station. These differences are 

 available in tide tables. 



tidal epoch — See epoch. 



tidal flat — A marsh or sandy or muddy coastal 

 flatland which is covered and uncovered by the 

 rise and fall of the tide. (2) 



tidal glacier — (or tideioater glacier). A glacier 

 whose terminus is in tidewater. (59) 



tidal inlet — See inlet. 



tidal movement — The movement which includes 

 both the vertical rise and fall of the tide, and 

 the horizontal flow of the tidal currents. This 

 movement is associated with tlie astronomical 

 tide-producing forces of the moon and sun act- 

 ing upon the rotating earth. 



tidal outlet — See inlet. 



tidal platform ice foot — Aji ice foot between 

 high and low water levels, produced by the rise 

 and fall of the tide. (68) 



tidal pool — A pool of water remaining on a beach 

 or reef after recession of the tide. (73) 



tidal prediction — See tide prediction. 



tidal pressure ridge — A pressure ridge in sea 

 ice caused by forces exerted on the ice by tlie 

 tide. (59) 



tidal prism — The difference between the mean 

 high water volume and tlie mean low water 

 volume of an estuary. 



tidal prism method — A theoretical procedure for 

 determining the flushing time of a harbor or 

 estuary. The method assumes that the contami- 

 nant is initially distributed uniformly through- 

 out tlie harbor or estuary, and that during each 

 tide cycle a volume of water and contained con- 

 taminant equal to the tidal prism is removed 

 from the harbor and replaced by a new volume 

 of sea water which mixes completely and uni- 

 formly with the water present in the estuary 

 at low water. Therefore, the amount of con- 



taminating material removed on each tidal cycle 

 may be expressed as a percentage of the con- 

 taminant in the harbor during the previous tidal 

 cycle : 



tidal prism volume 



high water volume of harbor 



X ( 100) =percent of con- 

 taminant re- 

 moved from 

 harbor. 

 tidal range — See tide range, 

 tidal rise — See rise of the tide, 

 tidal scour — The erosion of the bottom by tidal 

 currents with formation of deep channels and 

 holes. (2) 

 tidal stand — See stand of tide, 

 tidal stream — See tidal current, 

 tidal water — See tidewater, 

 tidal wave — 1. Tlie wave motion of the tides. 

 2. In popular usage, any miusually high (and 

 therefore destructive) water level along a shore. 

 It usually refers to either a storm surge or 

 tsunami; 



(5) 

 tide — The periodic rising and falling of the earth's 



oceans and atmosphere. It results from the 

 tide-producing forces of the moon and sun act- 

 ing upon the rotating earth. This disturbance 

 actually propagates as a wave through the at- 

 mosphere and through the surface layer of the 

 oceans. 



Atmospheric tides are always so designated, 

 whereas the term "tide" alone applies to the 

 water level. Sometimes, the periodic horizontal 

 movements of the water along coast lines is also 

 called "tide," but it is more correct to designate 

 the latter as tidal current, reserving the name 

 tide for the periodic vertical movements. 



tide amplitude — One-half of the difference in 

 height between consecutive high water and low 

 water; hence, half of the tide range. (5) 



tide bulge — See tide wave. 



tide crack — 1. A crack formed between shore ice 

 and the ice foot as a result of changing sea level. 

 (74) 



2. A crack between the moving sea ice and the 

 unmoving ice foot. It may widen to form a 

 shore lead. <S'ee crack. (5) 



tide curve — A graphic presentation of the rise 

 and fall of tide; time (in hours or days) is rep- 

 resented by the abscissa and height by the 

 ordinate. See marigram. 



C N 



T 1 1 T 1 1 r—^ — I r 



, MAXIMUM OIURNAl INEOUAIITY (HIGH WATER) 



6 



s ^ 



X 

 -2 



-AAAXUWM SOUTH DECLINATION 

 TIME LAO 



-CHART DATUM 



MAXIMUM DIURNAL INEQUALITY (LOW WATER) 



I TIME LAG ■ 1 



I I 1 I I L 



fl 



rt 



mmm- 



ESBJERG (SEMIDIURNAL TIDE) 

 I I I 



9 

 DAYS 



TYPICAL TIDE CURVE 



165 



