The modelled photosynthetically active radiation (PAR) is shown throughout the snow and ice layers at St.3 (dotted line), for fast ice stations (grey line), and for typical conditions in March (GoF ice, solid black line). Measured plane downwelling irradiance (E_d) over the surface is shown as a triangle (13-cm snow depth) at St.3 or a circle (5 cm snow depth) for typical conditions at these Gulf of Finland (GoF) stations in March.