Inhibition of the positive snow-albedo feedback by precipitation in interior Antarctica

• Published in: Nature climate change Vol. 2; no. 11; pp. 795 - 798
• Main Authors: Picard, G., Domine, F., Krinner, G., Arnaud, L., Lefebvre, E.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.11.2012; Nature Publishing Group
• Subjects: 704/106/125; 704/106/694; Absorption; Albedo; Climate Change; Climate Change/Climate Change Impacts; Earth and Environmental Science; Environment; Environmental Law/Policy/Ecojustice; letter; Metamorphism; Polar environments; Snow; Antarctica
• ISSN: 1758-678X; 1758-6798
• DOI: 10.1038/nclimate1590

This study uses satellite data to study snow grain size–albedo relationships over the whole Antarctic Plateau. The findings suggest that increased precipitation resulting from climate change will effectively compensate for the decreased albedo that should have resulted from warming, thereby inhibiting the expected ice–albedo feedback. The high albedo of snow largely determines the climate of polar regions by controlling energy absorption at the surface. In Antarctica, where light-absorbing impurities are few, snow albedo is mostly determined by the size of snow grains 1 . Snow metamorphism, the process of grain coarsening, occurs at a rate that increases with temperature 2 , 3 , so that snow albedo generally decreases as temperature increases. This increases energy absorption at the surface and atmospheric warming ensues, leading to a positive snow-albedo feedback. Here we use passive microwave satellite data and model outputs to show that this feedback is inhibited by small increases in precipitation. This is explained by the fact that grain coarsening in Antarctica is more sensitive to the deposition of small grains on the surface than previously assumed. We deduce that projected future increases in precipitation 4 can increase snow albedo by 0.4% on average during the twenty-first century and hence overcompensate the expected albedo decrease owing to warming (0.3% for 3 °C). Albedo-change projections in the Coupled Model Intercomparison Projects 3 and 5 do not reach a consensus on the sign and amplitude of this compensation, showing the need for a finer representation of the impact of precipitation on albedo in Antarctica.