Impacts of Autumn-Winter Tibetan Plateau Snow Anomalies on North Atlantic-Europe and Arctic Climate

Previous empirical studies have indicated strong influences of autumn and winter Tibetan Plateau (TP) snow cover extent (SCE) anomalies on the winter Pacific-North American (PNA) and also East Atlantic teleconnection patterns over the North Atlantic and Europe. Our early numerical experiments reproduced an observed wintertime PNA response to an extensive heavy TP snow anomaly. This study further investigates impacts of autumn-winter TP snow anomalies on North Atlantic-Europe and Arctic climate. Expressing snow conditions as snow water equivalent (SWE), observational analysis shows that the principal component time series associated with the leading empirical orthogonal function (EOF1) pattern of autumn TP SWE anomalies is significantly correlated to a remote equivalent barotropic tripole structure in winter, which resembles the negative phases of two teleconnections, North Atlantic Oscillation (NAO) at the surface and West Atlantic (WA) in the mid-troposphere. This indicates that the hydrological effect of TP SWE differs from the albedo effect of TP SCE in snow-atmosphere teleconnections. Numerical experiments using autumn TP SWE EOF1 and its persistent changes in winter as idealized snow forcing in a coupled atmosphere-ocean general circulation model simulate a winter negative NAO/WA response over the North Atlantic-Europe sector and a negative Arctic Oscillation over the Northern Hemisphere similar to observations. The NAO/WA responses result from mechanisms of horizontal propagation of stationary Rossby wave energy and a transient eddy feedback. Results also indicate that heavy TP SWE induces significant Eurasia cooling, and a consistent pattern of Arctic sea ice anomalies, demonstrating widespread Northern Hemispheric impacts of TP snow anomalies.

Automated summary

Previous empirical studies have shown that autumn and winter Tibetan Plateau snow cover anomalies have significant influences on winter Pacific-North American and East Atlantic teleconnection patterns. This study further investigates the impacts of these anomalies on North Atlantic-Europe and Arctic climate. Results indicate that the hydrological effect of Tibetan Plateau snow water equivalent differs from the albedo effect of snow cover extent in snow-atmosphere teleconnections. Numerical experiments using observed snow anomalies as forcing in a coupled atmosphere-ocean general circulation model simulate a winter negative NAO/WA response. These results demonstrate the widespread impacts of Tibetan Plateau snow anomalies on the Northern Hemisphere.