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New ice 
A general term for recently formed ice which includes frazil ice, grease ice, slush and 
shuga 
Number of days with ice 
Number of days with ice occurrence 
Open drift ice 
Drift ice with concentration of 4/10 to 6/10, with many leads and polynyas, and the 
floes are generally not in contact with each other 
Rafted ice 
Type of deformed ice formed by one piece of ice overriding another 
Reduced sum of ice 
In 1947/48, the reduced ice sum was introduced for the evaluation of ice winter severity in 
the German coastal regions. It constitutes the arithmetic mean of days with ice recorded 
at the 13 ice climatological stations and characterises the extent and duration of ice 
occurrence. 
Ridge 
A line or wall of broken ice forced up by pressure 
Ridged ice 
Ice piled haphazardly one piece over another in the form of ridges or walls 
Thin ice 
Ice with ice thickness less than 15 cm 
Very close drift ice 
Drift ice with concentration of 9/10 to less than 10/10