Figure 4

Underwater optical properties. (a) Downwelling irradiance for total shortwave, PAR and UVR; (b) transmittance as % downwelling incident irradiance in air; (c) reflectance as the ratio of upwelling to downwelling irradiance; and (d) diffuse attenuation coefficients under the summer ice of Ward Hunt Lake, 14 July 2016. The Kd values were plotted at z2; the Kd values for just below the ice (JBI) are ‘apparent attenuation coefficients’ because they were not corrected for reflection of incident light by the upper ice surface.