Regional response of winter snow cover over the Northern Eurasia to late autumn Arctic sea ice and associated mechanism

Variations of sea ice can exert significant impacts on the atmospheric general circulation, temperature and precipitation, resulting in anomalous land surface conditions such as snow cover. In this study, we explored the possible impacts of the abnormal late autumn Arctic sea ice on winter snow depth over the Eurasia, especially the mechanism responsible for regional response of the snow cover to the sea ice anomalies through both observational analysis based on multi-source snow depth data and numerical sensitivity experiments. Results show that with decreasing sea ice in the Barents and Kara Seas (BKS) region, the snow depth exhibits evident regional responses, which are featured by decreased snow depth in the North Eurasia but increased in central Europe. Further analysis suggests that the Arctic Oscillation (AO) is an important connection between the BKS sea ice and anomalous winter snow depth, which affect both the temperature and the precipitation in winter over the Eurasia. The regional difference mainly comes from significant differences in regional atmospheric general circulation anomalies as well as the various controlling factors affecting the formation of the snowfall. In North Eurasia, water vapor plays a decisive role in the formation of the winter snowfall and further the winter snow depth. Positive (negative) BKS sea ice anomaly generally induces positive (negative) AO pattern, which can enhance (weaken) the zonal wind and increase (decrease) water vapor transportation to the North Eurasia, causing increased (decreased) winter snow depth. In contrast, in Europe, temperature is the dominant factor affecting the formation of the snowfall and the snow depth. Positive (negative) AO pattern, enhances (weakens) the warm moist advection and thus leads to increased (decreased) temperatures in the Europe, consequently resulting in reduced (increased) winter snow depth.