Consequences of poor representation of Arctic sea-ice albedo and cloud-radiation interactions in the CMIP5 model ensemble



[1] Clouds significantly influence the Arctic surface energy budget and a realistic representation of this impact is a key for proper simulation of the present-day and future climate. Considerable across-model spread in cloud variables remains in the fifth phase of Coupled Model Intercomparison Project ensemble and partly explains the substantial across-model spread in the surface radiative effect of the clouds. In summer, the extensive model differences in sea-ice albedo, which sets the potential of the cloud-albedo effect, are strongly positively correlated to their cloud radiative effect. This indicates that the model's sea-ice albedo not only determines the amount, but also the sign of its cloud radiative effect. The analysis further suggests that the present-day annual amplitude of sea-ice cover depends inversely on the model's sea-ice albedo. Given the present-day across-model spread in sea-ice albedo and coverage, a transition to a summer ice-free Arctic ocean translates to a model-span of increased surface shortwave absorption of about 75 W m−2.