Some aspects of uncertainty in predicting sea ice thinning

A high proportion of the uncertainty in the decline of Arctic sea ice thickness in recent global climate models can be explained by the uncertainty in the ice thickness in the late 20th century. Experiments with one model indicate that this sensitivity to the mean state remains even when ice-albedo feedback is eliminated from the model. The magnitude of ice-albedo feedback is quantified and found to be too small to be a major source of uncertainty in thickness decline in climate models. Instead it is shown that the sea ice growth-thickness feedback in combination with large biases in the sea ice thickness during the 20th century can easily give rise to very large uncertainty in future thickness decline. Reducing biases in the surface fluxes and better tuning the surface albedo would improve uncertainty in both present and future prediction.