A New Sea-Ice Albedo Parameterization for ECHAM5 General Circulation Model

• Main Authors: Christina A. Pedersen, Erich Roeckner, Mikael Lüthje, Jan-gunnar Winther, C. A. Pedersen A
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; albedo; Sea ice
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.499.3559; http://munin.uit.no/bitstream/handle/10037/1909/paper_2.pdf;jsessionid=74DEF42A6436BB969B64B36E2E70D3DC?sequence=4

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 investigate a physically based sea-ice albedo scheme for ECHAM5 GCM, which separates be-tween snow covered sea ice, bare sea ice, melt ponds and open water (albedos and fractions separately). The new albedo scheme includes important components like 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 never been seen in general circula-tion models before, and represents a substantial improvement when simulating the annual cycle of sea-ice albedo. The new albedo scheme overall reduce the sea-ice albedo both in winter due to snow ageing and in summer due to melt ponds. The reduced sea-ice albedo leads to overall reduced sea-ice thickness, concentration and volume, with large temporal and spatial variations. In March, some areas experience increased albedo, resulting in thicker sea ice and higher ice concentration, but in August the pattern is more spatially homogeneous with reduced albedo, thickness and concentrations for all areas where the new scheme has a significant effect. Key words: sea ice albedo, general circulation model, melt ponds ∗ Corresponding author.