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Variations in water level
Those factors that we have shown earlier, that
make it difficult for organisms to survive in the beach environment, are
mainly due to the fact that the beach area is periodically flooded and drained
- tides. These variations can take place during a period of a few hours,
but at other times, the water level can remain unchanged over a period of
several days. In the long term,sea level changes with changes in climate
and land elevation.In the northern Baltic, where isostatic readjustment
is most pronounced, land elevation is about 1cm a year.
The highest high tide in relationship to the mean water level
ever recorded in Swedish waters was +181 cm at Kalix in 1984. The lowest
was -144 cm at Ystad in 1902.
In Swedish waters, recurrent changes in sea level are mainly
the result of three phenomenon:
Influx of water - Sometimes, the variations in the flow of
freshwater to the Baltic are so great, they effect sea level.
Tides - due to the gravitational pull (movement and attraction)
between the earth, sun and moon.
Weather - where differences in air pressure and wind intensity
transport water and cause a slight inclination of the sea surface.
The weather has most effect
In the farthest reaches of the Baltic, tidal
effect is of little importance, with variations of only a few centimetres.
However, tidal
differences increase further south in the Baltic, thereafter, even more
in a northerly direction along the Swedish west coast. In northern Bohuslän,
noticable tidal differences of up to 3 dm occurr twice daily.
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