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5.4 Sea ice 
Ice modelling is closely linked to the simulation of water temperatures. Therefore, the 
predicted ice distribution will be wrong if modelled water temperatures are not correct. 
Nevertheless, the support provided to the BSH's ice service becomes more important 
with increasing forecast length. BSHcmod simulates ice thermodynamics and dynamics 
based on forecasts from the DWD's numerical weather prediction models. Of special 
interest to the routine forecasting service is the temporal development of the computed 
parameters ice thickness and ice compactness. By comparing ice charts with model 
results, model predictions can be checked every day. Fig. 13 shows a comparison of 
measured (Strubing, pers. comm.) and computed ice distribution and thickness in the 
Baltic Sea on 26.03.2001. The ice extent and general distribution in nature and in the 
model are quite similar. Both model and ice chart show the thickest ice (30 - 50 cm) in 
the northern Gulf of Bothnia and eastern Gulf of Finland. Flowever, the location of the 
thickest ice differs in detail. Differences are also observed in other areas like the west 
coast of Finland. 
Measured ice thickness on 26.03.2001 BSH model forecast for 26.03.2001 
Fig. 13: Comparison of measured and predicted ice thickness classes in the Baltic Sea 
on 26 March 2001