Accelerated increase in the Arctic tropospheric warming events surpassing stratospheric warming events during winter

Abstract

In January 2016, a robust reversal of the Arctic Oscillation took place associated with a rapid tropospheric warming in the Arctic region; this was followed by the occurrence of a classic sudden stratospheric warming in March. The succession of these two distinct Arctic warming events provides a stimulating opportunity to examine their characteristics in terms of similarities and differences. Historical cases of these two types of Arctic warming were identified and validated based upon tropical linkages with the Madden-Julian Oscillation and El Nino as documented in previous studies. The analysis indicates a recent and seemingly accelerated increase in the tropospheric warming type versus a flat trend in stratospheric warming type. The shorter duration and more rapid transition of tropospheric warming events may connect to the documented increase in midlatitude weather extremes, more so than the route of stratospheric warming type. Forced simulations with an atmospheric general circulation model suggest that the reduced Arctic sea ice contributes to the observed increase in the tropospheric warming events and associated remarkable strengthening of the cold Siberian high manifest in 2016.

Plain Language Summary Rapid Arctic warming events disrupt mid-latitude weather patterns and oftentimes produce extreme deviations from normal weather conditions. The atmospheric origins of these Arctic warming events have been identified as developing in the troposphere and the stratosphere. Using historical observations, we have found that the frequency of tropospheric warming events has increased through the recent decades, while the stratospheric events have not. We have also found that tropospheric events develop twice as fast as stratospheric events and are therefore less predictable. With observations of historically-low Arctic sea ice extent occurring alongside the increase of tropospheric warming events, computer simulations provided evidence that the two phenomena are likely linked. Along with observational evidence for enhanced transport of tropical energy helping fuel these Arctic tropospheric warming events, these results suggest that future mid-latitude weather is likely to undergo an increase to extreme, unseasonal weather patterns that are inherently less predictable.