Partitioning uncertainty in projections of Arctic sea ice

Here, we consider the role of internal variability, model structure and emissions scenario in projections of Arctic sea-ice area (SIA) by using six single model initial-condition large ensembles and a suite of models participating in Phase 5 of the Coupled Model Intercomparison Project.

For projections of September Arctic SIA change, internal variability accounts for as much as 40%-60% of the total uncertainty in the next decade, while emissions scenario dominates uncertainty toward the end of the century. Model structure accounts for 60%-70% of the total uncertainty by mid-century and declines to 30% at the end of the 21st century in the summer months. For projections of wintertime Arctic SIA change, internal variability contributes as much as 50%-60% of the total uncertainty in the next decade and impacts total uncertainty at longer lead times when compared to the summertime.