Sea Ice Conditions in Gulf of Gdansk in 15 century 
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Sea Ice Conditions in Gulf of Gdansk in 15 century 
Marzenna Sztobryn 
Maritime Branch of Institute of Meteorology and Water Management in Gdynia, Poland 
Email Marzenna.Sztobrvn@imgw.Dl 
Abstract 
The aim of the work was the reconstruction of the sea ice conditions in the Gulf of Gdansk in 15 
century. Regular observations of sea-ice in this region reach as far back as the beginnings of 
20 century. For the time previous to 20 century reliable information can be also derived from 
written sources and by the comparison with information of sea-ice conditions in the Danish 
Straits. 
Introduction 
The sea ice conditions of the Baltic Sea are extremely sensitive to changes of climate 
(Sztobryn et al. 1997, Sztobryn, Krzymihski 1999). Knowledge of sea ice conditions’ variations 
in the scale longer than 100 years would enable to find out what changes of climate occurred in 
the past, in what manner they affected the coast infrastructure and also what we may expect in 
the future. The knowledge can be applied for calibration/verification of global and regional 
climate models. The Gulf of Gdansk, especially the Port of Gdansk (so-called Aurea Porta of 
the Both Nations’ Republic), has always been and still remains one of the most important water 
areas of Poland. The eventful history of this water area resulted in relatively great number of 
annals, in which one may find as well some notices on ice conditions, which can contribute to 
presentation of the changes’ analysis, worked out basing on the chronicler’s materials referring 
to Baltic freezing situations as well as to political changes, which took place therein. 
Thus, the basis for the study was materials and extracts made of various Polish, Ukrainian, 
Russian and Lithuanian chronicles. Through the extracts made by different authors, also the 
Danish and Swedish chronicles’ information became available. Owing to the above mentioned 
reporting, through comparison of ice conditions in 20 century (availability of daily observations), 
verification of a part of the notices became possible. 
Source materials 
To analyse the ice conditions in 20 century there have been used the observational data, from 
national services, mainly from the Danish, Polish and German. For evaluation of sea ice 
conditions which occurred in 15 century, the extracts of chronicles were applied. In general, the 
following works were examined: Walawender in Polish, Latin and former Ukrainian; Betin in 
Russian; Girgus in Polish and in Latin. Descriptions of winters and sea ice conditions included