Introduction 
9 
Fig. 1.3. a The geography of the western and southern regions of the Baltic Sea is shaped like 
a bay whose width changes from 25 nm at Wismar through 45 nm at Warnemünde, 60 nm at 
Sassnitz, and 90 nm at Swinoujscie to 120 nm at Kotobrzeg. 
ing water volume in the Baltic Sea. Both the 
magnitude and characteristics of sea level fluctu 
ations in the Baltic Sea depend, inter alia, on the 
particular coastline configuration, the exposure 
of different coastal stretches to the wind, the 
bathymetry of the adjacent sea basin, and on 
current patterns in the area. 
The most spectacular deformation of the water 
surface off the Baltic Sea shores is caused by 
stormy, hurricane-like winds. This occurs mostly 
when a strong low-pressure system tracks along 
or across the coast, as shown in the example in 
Fig. 1.3. b. In the morning of 4 December 1999, 
sea levels along the coasts of the Gulf of Gdansk 
(gauges Gdynia and Hel) were rising due to a 
storm following the passage of a cold front. At 
the same time, coastal water levels between Wis 
mar and Swinoujscie were falling as another per 
turbance approached. At about 05 UTC on this 
day, the difference of sea levels on this coast 
between Hel and Wismar exceeded 260 cm. The 
range between the extreme values, 600 cm in Hel 
on 02 UTC and 315 cm in Wismar on 05 UTC, 
approached 3 m (Fig. 1.3. c). 
Extremely low water levels are usually more 
extreme in Wismar than in Kotobrzeg, not only in 
this example. The explanation is found in the 
shape of the coast. As has been pointed out 
above, this part of the Baltic Sea is shaped like a 
bay. Therefore, a particular water volume 
removed from or added to the area affects a 
smaller area in the western part of the bay than in 
its eastern part. Consequently, because of this 
so-called bay effect, low water levels in the 
western part will be lower, and high water levels 
higher, than in the eastern part of the bay.