Baltic Sea Ice Climate Workshop 2005 
76 
Fig. 5. The development of the ice extent in the winter 2002/03 compared with the average of 
the ice phases for the period 1961 - 2000 
Restrictions to Navigation 
In order to keep the traffic running and to avoid delays by vessels not suited for winter 
navigation, restrictions to navigation have been introduced some decades ago by the Finnish 
and Swedish Maritime Administrations. This has been recently pushed again by the FIELCOM 
Recommendation 25/7 (adopted 2 March 2004) as result of the severe ice conditions 
experienced in the Gulf of Finland in 2003 (Mylly, M. 2004). The restrictions, i.e. special 
requirements with respect to the ice classification and size/power of the vessels, which allow 
them to receive Governmental icebreaker assistance, are set with respect to the severity of the 
ice conditions in the different sea areas. So, they may be used as a classification 
parameter/method for the character of an ice winter, too. An example is given in Figure 6. 
Restrictions to navigation Kemi + Oulu 
IA/2000 tdw and Ice extent 
250 t 
CM 
1990/91 1991/92 1992/93 1993/94 1994/95 
Ice winter 
No of days I A/200 EH Maximum extent Mean extent 
Fig. 6. Comparison of the duration 
of the restriction to navigation for 
the harbours Kemi and Oulu with 
the maximum and mean ice 
extents. 
The columns show that the number of days, when ice class IA and at least 2000 tdw where 
requested, relate somewhat to both ice extents. Flowever, by comparing the seasons 1992/93