6 
Summary 
Ice observations in Germany have been made routinely since the winter of 1896/97, and harmonised 
ice data from every winter season since 1899/1900 have been published in descriptions of the 
individual ice winters. By systematic evaluation and comparison of the data from a large number of 
coastal stations, it has been possible to derive conclusions as to possible periodic fluctuations or 
changes in ice occurrence in individual years or particular sections of the coast. 
Evaluations of the ice winter seasons have been published in chronological order in: 
Annalen der Hydrographie und Maritimen Meteorologie (except 1944, 1945) 
(annals of hydrography and maritime meteorology) 1900 - 1946 
Zeitschrift für Meteorologie 1947 
(journal of meteorology) 
Deutsche Hydrographische Zeitschrift (DHZ, German Journal of Hydrography) 
Annalen der Hydrographie (Berlin) (annals of hydrography) 
Special publications issued by the hydrographic office of the GDR 
Special publications issued by the coastal defence office of the GDR, 
Special publications issued by the water management directorate 1948 - 1999 
BSH Report No. 37 2000 - 2004. 
In addition, ice conditions in the German/Polish boundary waters (Szczecin Lagoon and Pomeranian 
Bight) have been evaluated and published in co-operation with the Ice Service of Poland in: 
BSH Report No. 20 (analysis of 30-year normal series) 1961 - 1990 
Deutsche Hydrographische Zeitschrift (DHZ, German Journal of Hydrography) 1995 - 1999 
BSH Report No. 37 2000 - 2002. 
In the present report, the past five ice winters from 2004/05 to 2008/09 are described. 
Ice winters on the German coasts are classified on the basis of the accumulated areal ice volume 
(V A j;), a number allowing scope and strength of the ice coverage, and the duration of ice occurrence 
(Koslowski, 1989), to be assessed. The observation stations providing data for the computation of 
(Vae) are shown in Figures 1 and 2. In the period from 1896/97 to 2003/04, there were 44 weak, 41 
moderate, 11 severe, 8 very severe, and 4 extremely severe ice winters. In the following five years, 
the ice winter of 2005/06 was moderate, and the winters of 2004/05, 2006/07, 2007/08, and 2008/09 
were all weak. Figures 3 and 4 show the distribution of accumulated areal ice volumes on the German 
North and Baltic Sea coasts since the 1896/97 winter season. The last very severe ice winter occurred 
in 1995/06, i.e. ice winters in the past 13 years have all been weak or moderate. 
The ice winter of 2007/08 deserves special mention: at the time of maximum ice coverage, only 
49,000 km 2 of the entire Baltic Sea area was covered with ice. This is the smallest maximum ice 
extent ever recorded since 1720, see Figure 5 (Seina and Palosuo, 1996). 
Irrespective of the general trend toward warmer weather conditions and decreasing ice formation in 
the Baltic Sea that has been observed in the past 20 years, very severe to extremely severe ice 
winters may occur also in the future. Comparable periods with predominantly weak to moderate ice 
winters have occurred frequently in the western part of the Baltic Sea during the 509-year period from 
1501 to 2009, cf. Figure 6 (Koslowski and Schmelzer, 2007).