Models fail to capture Arctic ice thinning, drift trends

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Observations have shown that Arctic sea ice extent has declined over the past several decades and that this decline has accelerated in recent years. However, climate models used in the Intergovernmental Panel on Climate Change (IPCC) fourth assessment report underestimate the observed decrease in ice extent. Furthermore, Rampal et al. studied 13 IPCC models and found that the models underestimate Arctic sea ice thinning by about a factor of 4 on average. In addition to thinning, observations show that Arctic sea ice is drifting more rapidly, but the authors found that the climate models do not capture this drift acceleration. The authors note that in most of the models, sea ice drifts faster when it is thicker, contrary to observations, which show thinner ice drifting faster. Faster drift increases the rate at which ice flows out of the Arctic. The models' weak coupling between ice thickness and drift velocity partly explains the models' underestimation of ice area, thickness, and velocity trends.