Fluctuations in Arctic Sea Ice Extent: Comparing Observations and CMIP5 Models.

We use a multi-fractal time series method to compare the fluctuation statistics of the observed sea ice extent during the satellite era with model output from CMIP5 models. The two robust features of the observations are that on annual to bi-annual time scales the ice extent exhibits white noise structure and there is a decadal scale trend associated with the decay of the ice cover. We find that (i) there is a large inter-model variability in the time scales extracted from the models, (ii) none of the models exhibit the decadal time scales found in the satellite observations, (iii) 4 of the 21 models examined exhibit the observed white noise structure, and (iv) the multi-model ensemble mean exhibits neither the observed white noise structure nor the observed decadal trend. We propose that the observed fluctuation statistics produced by our method serve as an appropriate test bed for modeling studies.