A Fair Assessment of Sea Ice Age Reduces Bias and Gives New Insight to Arctic Sea Ice Dynamics

Abstract The rapid Arctic warming in the early 2000s triggered a tremendous loss of multi‐year sea ice. Since then, sea ice age has been largely overlooked, despite its value in evaluating climate model skill in capturing sea ice dynamics. Comparing modeled sea‐ice age with observations is limited by differing methods for determining age, making fair comparison difficult. Here, we apply an ice‐tracking algorithm to diagnose sea ice age from daily concentration and drift data in a climate model and compare it to satellite‐derived estimates using the same method. We show that the derived sea ice age retains the spatial pattern and long‐term trends of the reported model age, but with less than half the bias. Changes in sea‐ice age highlight shifts in sea‐ice dynamics more clearly than thickness or volume. This shows that using a common algorithm enables both a fair model validation and improves insight into sea‐ice dynamics.