What caused the recent "Warm Arctic, Cold Continents" trend pattern in winter temperatures?​

Lantao Sun

Tuesday, Mar 15, 2016, 2:00 pm
DSRC Room 2A-305

Abstract

The emergence of rapid Arctic warming in recent decades has coincided with unusually cold winters over Northern Hemisphere (NH) continents. It has been speculated that this “Warm Arctic, Cold Continents” trend pattern is due to sea ice loss. Here we use multiple models to examine whether such a pattern is indeed forced by sea ice loss specifically, and by anthropogenic forcing in general. While we show much of Arctic amplification in surface warming to result from sea ice loss, we find that neither sea ice loss nor anthropogenic forcing overall to yield trends toward colder continental temperatures. An alternate explanation of the cooling is that it represents a strong articulation of internal atmospheric variability, evidence for which is derived from model data, and physical considerations. Sea ice loss impact on weather variability over the high latitude continents is found, however, characterized by reduced daily temperature variability and fewer cold extremes. Lastly, considering both significant Arctic sea ice loss and tropical El Nino conditions during the 2015/16 winter, we compare the impact of extreme sea ice loss and El Nino on NH extratropical climate. Our results indicate that Arctic sea ice loss warms the high-latitude continents through thermodynamical processes, in stark contrast to the dynamically driven influence by El Nino.