Optical properties of laboratory grown sea ice doped with light absorbing impurities (black carbon)

Sea ice radiative-transfer models are of great importance for prediction of future sea ice trends but they are limited by uncertainty in models and requirement for evaluation of modelled irradiance data against measured irradiance data. Presented here are the first results from the Royal Holloway sea ice simulator used to evaluate the output of the TUV-snow radiative-transfer model against the optical properties from the simulated sea ice. The sea ice simulator creates a realistic sea ice environment where both optical (reflectance and light penetration depth (e-folding depth)) and physical (temperature, salinity, density) properties of a ∼ 30 cm thick sea ice can be monitored and measured. Using albedo and e-folding depth data measured from simulated sea ice, scattering and absorption cross-sections of the ice are derived using the TUV-snow model. Absorption cross-sections for the ice are highly wavelength dependent, suggesting the addition of a further absorbing impurity in the ice matching the absorption spectrum of algae. Scattering cross-sections were wavelength independent with values ranging from 0.012 and 0.032 cm 2  kg −1 for different ice created in the simulator. Reflectance and light penetration depth (e-folding depth) of sea ice is calculated from the derived values of the scattering and absorption cross-section using the TUV-snow model within error of the experiment. The model is also shown to replicate ice optical properties for sea ice with an extra layer doped with black carbon, well within error of the experiment. Particulate black carbon at mass ratios of 75, 150 and 300 ng g −1 in a 5 cm ice layer lowers the albedo by 97 %, 90 %, and 79 % compared to clean ice at a wavelength of 500 nm.