Wintertime relationship between Antarctic sea ice and mid-high latitude atmosphere from an eddy activity perspective

The impact of Antarctic changes on the atmosphere in mid-high latitudes is a controversial topic, with little consensus on the processes and mechanisms involved. From the perspective of eddy energy, this study reveals that the interannual variability of Antarctic sea ice has a substantial impact on atmospheric eddy activities during the cold season, which in turn modulates the mean flow via eddy feedback. Specifically, the leading mode of Antarctic sea ice, characterized by a dipolar anomaly pattern, can affect eddy activities on both synoptic (2-8 days) and low-frequency (10-90 days) time scales. By comparing the total responses of eddy kinetic energy, results indicate that synoptic eddies contribute mainly to changes in Indian Ocean (58%) and Atlantic (38%) sectors, while low-frequency eddies contribute mainly to changes in Pacific (90%) and Atlantic (51%) sectors. This is further identified by diagnosing the eddy energy propagation through the Eliassen-Palm flux and wave activity flux. Moreover, the physical linkage between sea ice and transient eddy activities is established based on the anomalous surface turbulent heat flux and corresponding baroclinic processes. Subsequently, the anomalous geopotential height tendency dominated by eddy vorticity forcing generates and maintains the equivalent barotropic structure of atmospheric circulation. The results indicate that Antarctic sea ice could be a source of predictability for both weather and climate forecasts.