Assessment Of Arctic Sea Ice Simulation And Its Influence On The Atmospheric Circulation In CMIP5 Models

The Arctic sea ice cover has experienced an unprecedented decline since the late 20th century.As a result,the feedback of sea ice anomalies to atmospheric circulation has been increasingly evidenced.While the climate models almost consistently reproduce the downward trend of sea ice cover,great dispersion between them still exists.To evaluate the model performance in simulating Arctic sea ice and its potential role in climate change,we constructed a reasonable metric by synthesizing the linear trends and anomalies of the sea ice.We particularly focus on the Barents and Kara seas,where the sea ice anomalies have the greatest potential to feedback the atmosphere.Models can be grouped into three categories according to this criterion.The strong contrast among the multi-model ensemble means in different groups demonstrates the robustness and rationality of this method.The potential factors accounting for the different performance of climate models are further explored.The result shows that the model performance depends more on the ozone datasets prescribed by model rather than on the chemistry representation of ozone.The dominant mode,i.e.Arctic Oscillation(AO)for atmospheric circulation in northern hemisphere,was also assessed in CMIP5 models.The results of AO mode and AO vertical structure are compared with observation,showing that the models can roughly simulate the same tripolar shape of AO mode and reverse phase structure of southerly zonal wind and northerly zonal wind as observation.However,the location and strength of AO active centers of models' simulation still suffer large dispersion.It is found in observation that the wintertime AO has a significant response to BK sea ice anomaly in October and November.However,this atmospheric response to the change of BK sea ice is unsuccessfully simulated in most CMIP5 models.As for those with this atmospheric feedback mechanism,we find their simulations of AO are mainly affected by the results of BK anomaly in October and November.Therefore,the capability of the climate model to simulate the atmospheric circulation in northern hemisphere depends on its simulation of BK sea ice to some extent.