The Extraordinary March 2022 East Antarctica “Heat” Wave. Part I: Observations and Meteorological Drivers
Authors: Wille Jonathan D. , Alexander Simon P. , Amory Charles , Baiman Rebecca , Barthélemy Léonard , Bergstrom Dana M. , Berne Alexis , Binder Hanin , Blanchet Juliette , Bozkurt Deniz , Bracegirdle Thomas J. , Casado Mathieu , Choi Taejin , Clem Kyle R. , Codron Francis , Datta Rajashree , Di Battista Stefano , Favier Vincent , Francis Diana , Fraser Alexander D. , Fourré Elise , Garreaud René D. , Genthon Christophe , Gorodetskaya Irina V. , González-Herrero Sergi , Heinrich Victoria J. , Hubert Guillaume , Joos Hanna , Kim Seong-Joong , King John C. , Kittel Christoph , Landais Amaelle , Lazzara Matthew , Leonard Gregory H. , Lieser Jan L. , Maclennan Michelle , Mikolajczyk David , Neff Peter , Ollivier Inès , Picard Ghislain , Pohl Benjamin , Ralph F. Martin , Rowe Penny , Schlosser Elisabeth , Shields Christine A. , Smith Inga J. , Sprenger Michael , Trusel Luke , Udy Danielle , Vance Tessa , Vignon Étienne , Walker Catherine , Wever Nander , Zou Xun 
Published: November 2023

Abstract
Between 15 and 19 March 2022, East Antarctica experienced an exceptional heat wave with widespread 30°–40°C temperature anomalies across the ice sheet. This record-shattering event saw numerous monthly temperature records being broken including a new all-time temperature record of −9.4°C on 18 March at Concordia Station despite March typically being a transition month to the Antarctic coreless winter. The driver for these temperature extremes was an intense atmospheric river advecting subtropical/midlatitude heat and moisture deep into the Antarctic interior. The scope of the temperature records spurred a large, diverse collaborative effort to study the heat wave’s meteorological drivers, impacts, and historical climate context. Here we focus on describing those temperature records along with the intricate meteorological drivers that led to the most intense atmospheric river observed over East Antarctica. These efforts describe the Rossby wave activity forced from intense tropical convection over the Indian Ocean. This led to an atmospheric river and warm conveyor belt intensification near the coastline, which reinforced atmospheric blocking deep into East Antarctica. The resulting moisture flux and upper-level warm-air advection eroded the typical surface temperature inversions over the ice sheet. At the peak of the heat wave, an area of 3.3 million km2 in East Antarctica exceeded previous March monthly temperature records. Despite a temperature anomaly return time of about 100 years, a closer recurrence of such an event is possible under future climate projections. In Part II we describe the various impacts this extreme event had on the East Antarctic cryosphere.

Significance Statement
In March 2022, a heat wave and atmospheric river caused some of the highest temperature anomalies ever observed globally and captured the attention of the Antarctic science community. Using our diverse collective expertise, we explored the causes of the event and have placed it within a historical climate context. One key takeaway is that Antarctic climate extremes are highly sensitive to perturbations in the midlatitudes and subtropics. This heat wave redefined our expectations of the Antarctic climate. Despite the rare chance of occurrence based on past climate, a future temperature extreme event of similar magnitude is possible, especially given anthropogenic climate change.