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9. Ice growth in Szczecin Lagoon 
The study „Ice conditions in the Szczecin Lagoon and Pomeranian Bay during the normal period 1961- 
1990“ (Sztobryn, Stanistawczyk, Schmelzer, 1999) provided an analysis of the ice data of the 30-year 
observation period from 1961 - 1990. It contains computations of mean and extreme values for various 
ice parameters and three types of ice winter - mild, normal, and strong to very strong - and presents 
empirical equations for a theoretical determination of ice thicknesses in Szczecin Lagoon. In the following, 
some of the mean values and equations derived from the 1961-1990 data will be checked against 
measurements made in the past 13 years. All three types of ice winter occurred in the past 13 years: mild 
ice winters in 1991/92, 1992/93, 1994/95, 1997 /98, 1998/99, 1999/2000, 2000/01, 2001/02; normal 
winters in 1990/91, 1993/94, 1996/97, and 2002/2003; the category of strong to very strong winters was 
represented by the strong winter of 1995/96. 
Cold sum in °C 
Figure 9.1. Dependence of the mean maximum ice thickness on the cold sum in Szczecin Lagoon 
h max = 2.12* K s - 5.36 and measured mean maximum ice thickness in the winters of 1990/91, 1991/92, 
1992/93, 1993/94, 1994/95, 1995/96, 1997 /98, 1998/99, 1999/2000, 2000/01, 2001/02, and 
2002/2003 
Figure 9.1 shows the mean maximum ice thicknesses measured in Ueckermunde, Karnin and 
Kamminke in the ice winters of 1990/91, 1991/92, 1992/93, 1993/94, 1994/95, 1995/96, 1996/97, 
1997/98, 1998/99, 1999/2000, 2000/01, 2001/02, and 2002/2003 plotted against the cold sums in 
those years (Sztobryn et al., 1999). It can be seen that the empirically found curve represents most 
maximum ice thickness measurements with adequate precision. 
Another fact to be noted is the following: the observed dependence of maximum ice thicknesses on 
the cold sum is based on data from the 1961-1990 winters. When studying the variability of ice winters 
in Szczecin Lagoon (in: Ice Conditions in the Szczecin Lagoon and Pomeranian Bay During the Winter 
of 1999/2000, this issue), a slight downward trend of maximum ice thicknesses at the peak of ice de 
velopment was observed. However, this observation is attributable rather to an increase in winters with 
weak ice development during the past 30 years. The maximum ice thicknesses measured in moderate 
or strong to very strong ice winters reach the same values today as 50 years ago. This is confirmed in 
Figure 1: the correlation between the theoretical values computed by means of the equation h max = 
2.12* K s ' 2 - 5.36 and the maximum ice thicknesses measured in the past 13 winter seasons is 0.96. 
Figure 9.2 shows the dependence of thermally developed ice thicknesses on the cold sums in mild 
ice winters. There is no major difference in the trend of the „old“ and „new“ empirical equations. How 
ever, the ice thicknesses measured at all three stations in the winters of 1999/00 and 2000/01 are 
clearly below the theoretically computed values. In the short periods with negative air temperatures in