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Modeling Arctic Sea Ice Albedo Under Summer Conditions
Koenigk, T., Devasthale, A., Karlsson, K.-G. 2014. Summer Arctic sea ice albedo in CMIP5 models. Atmospheric Chemistry and Physics 14: 1987-1998.

Citing Winton (2006) and Serreze et al. (2009), the authors say "it seems to be beyond question that the ice-albedo feedback is an important contributor to Arctic temperature amplification and changes in sea ice conditions," while noting that "the observed Arctic temperature amplification compared to lower latitudes has led to an intensive discussion on the role of the surface albedo," citing the additional study of Riihela et al. (2013b).

What was done
As for their role in broaching the subject, Koenigk et al. "used the surface albedo product from the Satellite Application Facility on Climate Monitoring (CM-SAF) clouds, albedo and radiation data set (CLARA-SAL, Ruhela et al., 2013a; Karlsson et al., 2013) and sea ice concentration from the Ocean and Sea Ice Satellite Application Facility (OSI-SAF) data set (Eastwood et al., 2010) as comparison for the model data," which were derived from 21 different CMIP5 models.

What was learned
In reporting their long list of results, the three Swedish researchers write that (1) "summer sea ice albedo varies substantially among CMIP5 models," that (2) "many models show large biases compared to the CLARA-SAL product," that (3) "single summer months show an extreme spread of ice albedo among models," that (4) "July values vary between 0.3 and 0.7 for individual models," that (5) "the CMIP5 ensemble mean ... shows too high ice albedo near the ice edges and coasts," that (6) "in most models, the ice albedo is spatially too uniformly distributed," that (7) "the summer-to-summer variations seem to be underestimated in many global models," that (8) "almost no model is able to reproduce the temporal evolution of ice albedo throughout the summer fully," that (9) "while the satellite observations indicate the lowest ice albedos during August, the models show minimum values in July and substantially higher values in August," that (10) "June values are often lower in the models than in the satellite observations," due to (11) "too high surface temperatures in June," leading to (12) "an early start of the melt season and too cold temperatures in August causing an earlier refreezing in the models," such that (13) "the impact of the ice albedo on the sea ice conditions in the CMIP5 models is not clearly visible."

What it means
In light of their several findings, Koenigk et al. conclude that "the Arctic climate system can thus not correctly be simulated (other than with compensating errors) if the large-scale atmospheric and oceanic circulation determining the input of mass, heat and momentum into the Arctic is not correctly simulated." And they also remark that "strong tuning of the albedo in order to achieve realistic Arctic ice and climate conditions in 20th century simulations might lead to unrealistic amplification rates in future simulations." When shopping for Arctic sea ice models, therefore, the word on the street is buyer beware!

Eastwood, S., Larsen, K.R., Lavergne, T., Nielsen, E. and Tonboe, R. 2010. Global Sea Ice Concentration Reprocessing: Product User Manual. Product OSI-409, Version1.

Karlsson, K.-G., Riihela, A., Muller, R., Meirink, J.F., Sedlar, J., Stengel, M., Lockhoff, M., Trentmann, J., Kaspar, F., Hollmann, R. and Wolters, E. 2013. CLARA-A1: a cloud, albedo, and radiation dataset from 28 yr of global AVHRR data. Atmospheric Chemistry and Physics 13: 5351-5367.

Riihela, A., Manninen, T., Laine, V., Andersson, K. and Kaspar, F. 2013a. CLARA-SAL: a global 28 yr timeseries of Earth's black-sky surface albedo. Atmospheric Chemistry and Physics 13: 3743-3762.

Riihela, A., Manninen, T. and Laine, V. 2013b. Observed changes in the albedo of the Arctic sea-ice zone for the period 1982-2009. Nature Climate Change 3: 895-898.

Serreze, M.C., Barrett, A.P., Stroeve, J.C., Kindig, D.N. and Holland, M.M. 2009. The emergence of surface-based Arctic amplification. The Cryosphere 3: 11-19.

Winton, M. 2006. Amplified Arctic climate change: What does surface albedo feedback have to do with it? Geophysical Research Letters 33: 10.1029/2005GL025244.

Reviewed 11 June 2014