Amplified winter Arctic tropospheric warming and its link to atmospheric circulation changes

Abstract

The physical cause of amplified deep Arctic tropospheric warming in winter in the Barents–Kara Seas (BKS) is examined. The authors propose that changes in the atmospheric circulation patterns are important for deep Arctic tropospheric warming in winter. It is found that the retrograde Urals blocking (UB) event concurrent with a negative North Atlantic Oscillation (NAO−) that arises from a prior negative Arctic Oscillation (AO−) is not favorable for tropospheric warming because of less water vapor over the BKS. Such UB events are related to more winter BKS sea ice associated with the negative sea surface temperature (SST) anomaly in the BKS. In contrast, a UB occurring together with a positive North Atlantic Oscillation (NAO+) shows less movement and can significantly enhance tropospheric warming over the BKS through increasing tropospheric sensible heat energy due to a persistent BKS water vapor increase. This type of quasi-stationary UB event is related to prior less BKS sea ice associated with a positive BKS SST anomaly that coexists with the North Atlantic SST tripole structure. In summary, because warm, wet and low sea-ice winters in the BKS are related to UB events with an NAO+, and depend on the winter prior sea-ice condition, the tropospheric warming is to some extent a manifestation of the sea-ice–blocking–moisture feedback in the BKS.

Keywords

• Arctic warming
• Ural blocking
• NAO
• water vapor
• sensible heat energy