The changing albedo of the Greenland ice sheet: implications for climate modeling

Although the snow albedo feedback mechanism has been shown to amplify global warming effects in nearly all models of global climate, it continues to be represented as a simplistic parameterization. Here, we demonstrate how changes in snow-pack energy-balance drive the seasonal fluctuations in snow albedo for the Greenland ice sheet. For a detailed, point-based investigation of the relationship between snowpack energy balance and albedo, two models are coupled together; one that calculates snow grain-size and the other that uses those grain-size data as input to a radiative-transfer code to obtain spectral albedo. These data indicate that in the near-infrared wavelengths, albedo values drop nearly 20%, during a 10 day period during which grain-sizes increased dramatically. Satellite data were used to map monthly changes in albedo over the entire Greenland ice sheet during the spring and summer months. These monthly albedo images indicate albedo reductions of as much as 80% in coastal regions. Even in areas that experience little or no melt, albedo decreases of 10–20% were common. From these results, it is clear that snow albedo parameterizations for climate models must incorporate the dynamics of snowpack energy balance.