Supplementary material to "Solar radiative transfer in Antarctic blue ice: spectral considerations, subsurface enhancement, and inclusions"

Abstract

S1 Solar zenith angle dependence Here we investigate the influence of the incident solar zenith angle (SZA). For simplicity, the results presented in the main text have relied on the assumption that the incoming solar flux arrives from a diffuse hemispherical sky, with no direct component. However the angular dependence of Fresnel reflection coefficients at the ice-air interface may cause the solar flux within the ice to be sensitive to the solar zenith angle, irrespective of the absolute shortwave irradiance. To test this the model is rerun with a set of specific solar zenith angles covering the expected range experienced at the Frontier Mountain range (from 49° to 89° at 10° intervals) with the mean bubble parameter set in all cases. In Fig. S1a the impact of this change can be seen in the reduction of solar flux with increasing SZA, particularly at the highest angle of incidence. Also shown are the results for a diffuse sky which lies close to the 69° result. The reduction in the downwelling fluxes is principally due to the high incidence angle rather than an increased scattering path c.f. the vertical depth. This is expected as after 1 (1 −) ⁄ scattering events, the radiation field can be considered isotropic and retains no information of the initial beam direction. In