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Wintertime Extreme Warming Events in the High Arctic: Characteristics, Drivers, Trends, and the Role of Atmospheric Rivers

Presentation Date
Thursday, December 14, 2023 at 2:10pm - Thursday, December 14, 2023 at 6:30pm
MC - Poster Hall A-C - South



An extreme warming event, with surface air temperature above the melting point, was observed near the North Pole in late December 2015. It has been found that cyclones and their associated moisture intrusions were responsible for this specific event. However, little is known about the characteristics and drivers of similar events in the historical record. Here, using hourly data from ERA5, we conduct a detailed study on these winter extreme warming events with the 2-meter air temperature above the melting point over the high Arctic (poleward of 80°N) occurred during 1980-2021. In ERA5, such extreme events can only be found over the Atlantic sector. The seasonal mean occurrence frequency was less than one event over most of the regions. Furthermore, consistent with the event occurred in late December 2015, all extreme warming events tend to be short-lived, with majority of the events lasting for less than a day. By examining their surface energy budget, we found that these events transit from a regime dominated by turbulence heat flux to the one dominated by downward longwave radiation as latitude increases. Atmospheric blockings over the northern Eurasia are identified as a key ingredient in driving these events, as they can effectively deflect the eastward propagating cyclones poleward, leading to intense moisture and heat intrusions into the high Arctic. Using an atmospheric river (AR) detection algorithm, the roles of ARs in driving these events are explicitly quantified. The importance of ARs in facilitating these events increases with latitude. Poleward of about 83°N, ARs are responsible for 100% of these events, corroborating the indispensable roles ARs played in driving these events. Over 1980-2021, the frequency, duration, and magnitude of these events all have been increasing significantly. As the Arctic continues to warm, such extreme warming events are likely to increase, which will have great implications for the Arctic sea ice, hydrological cycle, ecosystem as well as the global climate.

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