The Effects of Bubbles and Biotic Impurities on Snow and Ice Radiative Transfer Properties

Abstract:

The Greenland Ice Sheet (GrIS) has been losing mass rapidly over the past few decades, mostly due to increasing surface melt. Surface melt is strongly influenced by the albedo of the ice sheet surface. The albedo declines naturally with increased temperatures and reduced solar zenith angles in the spring and summer as the snow ages and melts to expose the dark bare ice beneath the winter snow. Light absorbing impurities, such as darkly pigmented algae, within the snow and ice also reduce the albedo. Snow and ice algae absorb solar radiation and cause substantial surface melt. However, radiative transfer models have not yet been adequately adapted to represent the physical radiative properties of bare ice and light absorption by ice algae. This work uses physical properties of ice, snow, and cryospheric algae to expand the offline SNow ICe and Aerosol Radiative - Adding Doubling (SNICAR-AD) model to more accurately represent the albedo of snow and ice surfaces. Our updated model allows us to quantify the contributions from cryospheric algae to changes in albedo on snow and ice surfaces and will in turn increase our ability to accurately model GrIS melt. We will show a preliminary evaluation of the SNICAR-AD biologically enabled model over a range of bare ice conditions, including varying bubble concentrations, surface scattering layer thicknesses, and algal concentrations.