Influence of the Temperature on Ice Conditions in the Bay of Bothnia (Baltic Sea) 
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Influence of the Temperature on Ice Conditions in the Bay of Bothnia 
(Baltic Sea) 
Élise LÉPY 
Laboratory GEOPHEN 
University of Caen - Basse-Normandie (France) 
elise.lepv@unicaen.fr 
Abstract 
Every winter, the ice sea is formed in the Bay of Bothnia (North of the Baltic Sea). The ice 
growth and melting processes of its waters are submitted to the northern climate with oceanic 
and continental influences. Temperature is an essential parameter to the formation of the ice 
pack, but is it the only element to have an influence on these processes? The statistical 
analysis of the correlation between temperature and ice conditions is necessary to understand 
the influence of other natural and anthropogenic elements on ice growth and melting in the Bay 
of Bothnia. 
Key words: Ice growth, ice break-up, temperature, correlation, Bay of Bothnia 
Introduction 
Interior sea belonged to Europe, the Baltic Sea is the only one in which a state change process 
of its waters happens every year. In fact, waters of the Gulfs of Bothnia, Finland and Riga 
freeze every winter. Thus, seasonal processes of ice growth and melting can be observed each 
year and have an important role in the economic life - especially in the winter navigation- in all 
the countries close to these gulfs. 
During the winter, “the maximum annual ice extent is 10 to 100% of the Baltic area, the length 
of ice season is 4 to 7 months, and the maximum annual thickness of landfast ice is 50 to 120 
centimetres” (Jevrejeva, 2004). The ice pack is an important element in the climatology of the 
Baltic Sea (Haapala, Lepparanta, 1997). The ice growth of the sea has an influence on the 
climate which becomes more continental. The difference between the mean temperature of the 
warmest and coldest months of the year is an indicator of continentality (Autio, Heikkinen, 
2002). In the Bay of Bothnia, the temperature difference is 21,3 to 37,1 t C; the mean is 28,8^ 
for the period 1957-2004 (mean monthly temperatures at Oulu airport station). Moreover, the 
sea ice “plays an important role in the North-European climate” (Flaapala, Lepparanta, 1997). 
Sea ice conditions are an indicator of the severity of the winter season (Flaapala, Lepparanta, 
1997). Nevertheless, the climatic parameter of temperature is it the only element which has an 
influence on the spatial and temporal variability of the ice growth and melting? The purpose of 
this paper is to analyse the interactions between climatic variables and cryomarine phenomena, 
and to discern others parameters to take care in the formation of the ice cover. 
Data and methods 
The ice growth and melting processes in the Bay of Bothnia is the main point of this paper. 
Temperature is an essential parameter for the ice to be formed. It seems interesting to