A new sea ice albedo scheme including melt ponds for ECHAM5 general circulation model

• Published in: Journal of Geophysical Research
• Main Authors: Pedersen, C., Roeckner, E., Luthje, M., Winther, J.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2009
• Subjects: Arctic; albedo; Sea ice
• Online Access: http://hdl.handle.net/11858/00-001M-0000-0011-F807-9; http://hdl.handle.net/21.11116/0000-000B-482E-2

Today we experience an accelerated melting of sea ice in the Arctic which global circulation models are inadequate to predict. We believe one of the reasons is the shortcomings in the sea ice albedo schemes for these models. This paper investigates a physically based sea ice albedo scheme for ECHAM5 GCM, which separates between snow-covered sea ice, bare sea ice, melt ponds, and open water (separately for the albedos and albedo fractions). The new albedo scheme includes important components such as albedo decay due to snow aging, bare sea ice albedo dependent on the ice thickness, and a melt pond albedo dependent on the melt pond depth. The explicit treatment of melt pond albedos has, to our knowledge, not been included in general circulation models before and represents a substantial improvement when simulating the annual cycle of sea ice albedo. The new albedo scheme overall reduces the sea ice albedo both in winter, because of snow aging, and in summer, because of melt ponds. The reduced sea ice albedo leads to overall reduced sea ice thickness, concentration, and volume, with large temporal and spatial variations. In the Northern Hemisphere in March, some areas experience increased albedo, resulting in thicker sea ice and higher ice concentration, but in August the pattern is spatially homogeneous, with reduced albedo, thickness, and concentrations for all areas where the new scheme has a significant effect. [References: 57]