Different climatic effects of the Arctic and Antarctic ice covers on land surface temperature in the Northern Hemisphere: application of Liang-Kleeman information flow method and CAM4.0

Ice covers in high latitudes play important role in the global atmospheric circulation and abnormal temperature distribution. The different inter-annual variabilities of the Arctic and Antarctic ice covers have been revealed, but their respective climate effects are not clear. The Liang-Kleeman information flow method is used to reveal the causal relationships from the sea ice to the surface air temperature. The results point out that the Arctic and Antarctic sea ice both have significant impacts on the global air temperature. Especially in East Asia and North America, the inter-annual variation of ice cover in the Antarctic has an even stronger impact than that of the Arctic. This causality is further proved by the General Atmospheric Circulation Model (CAM4.0). In the numerical experiments, the ice covers in Arctic and Antarctic are changed individually or simultaneously as the forcing fields, and then the corresponding climate effects are analyzed. The results show that the Arctic and Antarctic ice cover variations can change the intensity of atmospheric baroclinic disturbance in mid-high latitudes of individual hemisphere, generating wave energy transmission across the equator through the wave-train-window over the Eastern Equatorial Pacific, and eventually causing air temperature anomalies in another hemisphere. Furthermore, the Antarctic ice covers are closer to the mid-high latitude atmospheric jets in the southern hemisphere. Therefore, compared to the Arctic ice cover, the inter-annual changes of Antarctic ice cover lead to a larger atmospheric wave-activity flux response, quickly (less than two months) spreading to the northern hemisphere, and causing more significant air temperature anomalies over the East Asia and North America. However, the influence of the inter-annual variability of Arctic ice cover on the climate in the southern hemisphere requires a lag time of at least four months, and the intensity is relatively weak.