Some Ideas on Sea Ice Climate and Navigation in the Baltic Sea 
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Table 4. The extent and the first, mean and average dates of ice phases and the area and 
date of the maximum ice extent (1960/61 -1999/2000) 
Dates of the occurrence of ice phases and the extent of their ice coverage in the northern region of the Baltic Sea for the period 1960/61 - 1999.2000 (with data of FMR 254,1988) 
For technical reasons the dates in the columns 1-20 are given in the form mm.dd. (month.day.) 
In the column for the maximum ice extent the numbers for the whole Baltic Sea are listed (Selna, A., 
Palosuo, E., 1993), while the ice extent for the phases is calculated for the northern region only. 
A - average, EM - extreme mild, ES - extreme strong, M - mild, S - strong ice winter 
Numbers 1-10 and 12-20: phase no. 
Column 11: date of the maximum ice extent 
Blue sector: The maximum ice extent was less than the extent of the phases related to this sector. If 
dates are given in this sector, see note below. 
The basic reason is that e. g. a winter with a rather great maximum ice extent can have only 
short periods with the greater extent and vice versa. However, beside that - as result of the 
calculation with the ice extent for the single phases, some discrepancies with the official values 
for the maximum ice extent have been found as well as with some data given in Table 1 of the 
‘Phase Atlas’ (note: these discrepancies are presently under negotiation. Therefore, so far the 
given values in this paper have to be considered as preliminarily). For example, in the ice 
winter 1973/74 the maximum ice extent is given as 94,000 km 2 . This value does not fit with the 
data from the ‘Phase Atlas’ that on January 20 phase 6 was reached, the extent of which is 
calculated to be about 135,000 km 2 . As the retreat of the ice is given to start with phase 16 
(about 85,000 km 2 ), which is within the range of the given maximum ice extent, the ice charts 
for that ice season have been checked, and as a result it is suggested to delete phase 6. On 
the other hand, for the winter 1970/71 the phases 8 and 13-14, respectively, could be