Sea Ice Conditions in Gulf of Gdansk in 15 century 
59 
Table 1. The mean and extreme data referring to freezing (for winters with ice) at the Gulf of 
Gdansk (Gdansk water area) within a period 1922-2000 
First sea ice 
Last sea ice 
the 
earliest 
on the 
average 
the 
latest 
the 
earliest 
on the 
average 
the latest 
28.12 
26.01 
8.03 
31.12 
28.02 
10.04 
Number of days with ice 
Duration of ice season (days) 
min 
on the 
average 
max 
min 
on the 
average 
max 
1 
10 
76 
1 
16 
86 
At the Gdansk fairway, ice appeared on 28 December 1961 at the earliest, whereas at the 
latest the first ice was observed on 8 of March in winter 1970/71. Ice melting at the earliest 
occurred on 31 December in winter 1923/24, also in 1966/67 and 1996/97 seasons. In this 
water area, at the latest ice was melted on 10 April in winter 1955/56. 
The maximal number of days with ice was 76 and occurred in very severe winter 1962/63. Also 
a high number of days with ice was observed in winter 1941/42 (73 days), it means of the same 
severity. On the contrary, the longest lasting ice season was reported in winter 1961/62, when 
ice appeared already 28 December and melted 23 of March. In connection with a possibility of 
multiple sea ice forming and melting in one winter season, for a majority of ice seasons a 
number of days with ice is lower or equal to the duration of ice season. 
Comparison of Sea Ice Conditions on the Gulf of Gdansk with Danish Straits 
Regular daily observations of sea ice conditions (according to the codes jk, ijk, astk) of the 
Baltic Sea were begun either in 19 century or in the early part of 20 century, therefore the 
available comparative material is very broad. There has been carried out a comparison of 
numbers of days with ice for 3 main fairways of the Gulf of Gdansk (Gdansk, Hel and Gdynia) 
and a cold sum for all Danish water areas and the days with sea ice on open water as well as in 
the ports located in open water areas (Fig.1).