In mid-winter, the Gulf of Finland and the Gulf of Bothnia are covered by an ice sheet measuring thousands of square kilometres. As these icy expanses are pushed by the wind towards the far ends of the Gulfs, the fast ice breaks up into blocks, creating pack ice ridges even kilometres long. Generally known as the sail, the part of the ridge visible above the surface forms a protrusion often 0.5 to 2 metres high. Underneath is hidden the keel, an underwater block of ice perhaps even 10 times thicker and often reaching the sea bed. The largest ice ridge measured in the Baltic Sea reached a depth of over 30 metres.

Under pack ice, the photographer encounters a still, silent world. In the gloom, the blocks of pack ice glow in neon and pastel tones, as if lit from within. On film, the variegated tones of pack ice are often difficult to capture authentically. A digital sensor is better at replicating these colours.