Abstract
Reduction of snow and ice albedo causes a drastic mass loss of glaciers and the ice sheet in the Arctic region. The albedo of snow and ice is greatly reduced by inorganic impurities, such as aeolian mineral dust and black carbon, and also by organic impurities, such as microbes that live in the snow and ice. The effect of such biological impurities is called the bio-albedo effect, which can be found globally on glaciers and snowfields. The bio-albedo effect varies temporally and spatially due to its biological properties including growth, death, and migration. In addition, the bio-albedo effect shows distinctive spectral absorption due to various pigments contained in the cells. To quantify the bio-albedo effect, a physically based albedo model and a microbial growth model have been proposed by different studies recently. In this paper, we describe the mechanism of the bio-albedo effect and review its recent observations and model studies. The paper finally discuss future challenges in understanding and predicting the darkening of glaciers and ice sheet in the Arctic region.
