Diffuse Attenuation Coefficients for East Antarctic Pack Ice and Snow at Ultraviolet and Visible Wavelengths

Declining stratospheric ozone concentrations have led to higher levels of ultraviolet (UV) B (UVB) radiation at the Earth´s surface, particularly in Antarctic spring time. Increased exposure to UVB radiation can decrease the productivity of sea-ice algae, as well as cause damage to organisms living in the clear water beneath the Antarctic pack ice. Conversely, sea-ice algae and other photosynthetic organisms rely on photosynthetically active radiation (PAR) to drive and sustain growth. Field work performed during the 2007 Australian Antarctic Program Sea Ice Physics and Ecosystem eXperiment voyage to the East Antarctic sea-ice zone allowed the estimation of diffuse attenuation coefficients for pack ice and the overlying snow at UV wavelengths (305, 313, 320, 340, 380, and 395 nm) and for PAR. The UV attenuation coefficients were 9.6-12.7 m^-1 for snow and 1.57-2.05 m^-1 for pack ice. The PAR attenuation coefficients were 10.5 m^-1 (snow) and 1.52 m^-1 (pack ice). The attenuation coefficients for erythemally weighted UVB radiation were 11.3 m^-1 (snow) and 1.82 m^-1 (pack ice). The analysis also estimated the reflection coefficient (albedo) of snow as 0.67 for UV wavelengths and 0.68 for PAR, but the snow cover was not always optically thick.