This report presents sea ice core measurements taken from the Bothnian Bay, March, 1984. The measurements were taken at different sites in the skerries and the basin area. The ice cores were analysed with respect to crystallographic structure using polarized light. Some ice cores were also used for the determination of ice density and ice salinity. The data give a good insight into the ice structure in a sea ice cover, illustrating a complex structure with ice types of different origins, mixed and stratified within the ice cores.

The ice cores were classified with a structural scheme. In that scheme, the sea ice is classified into three main groups: granular ice, columnar ice and mixed ice. In the examined ice cores all three groups were well represented.