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L. C. Shaffrey
,
I. Stevens
,
W. A. Norton
,
M. J. Roberts
,
P. L. Vidale
,
J. D. Harle
,
A. Jrrar
,
D. P. Stevens
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M. J. Woodage
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M. E. Demory
,
J. Donners
,
D. B. Clark
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A. Clayton
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J. W. Cole
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S. S. Wilson
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W. M. Connolley
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T. M. Davies
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A. M. Iwi
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T. C. Johns
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J. C. King
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A. L. New
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J. M. Slingo
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A. Slingo
,
L. Steenman-Clark
, and
G. M. Martin

Abstract

This article describes the development and evaluation of the U.K.’s new High-Resolution Global Environmental Model (HiGEM), which is based on the latest climate configuration of the Met Office Unified Model, known as the Hadley Centre Global Environmental Model, version 1 (HadGEM1). In HiGEM, the horizontal resolution has been increased to 0.83° latitude × 1.25° longitude for the atmosphere, and 1/3° × 1/3° globally for the ocean. Multidecadal integrations of HiGEM, and the lower-resolution HadGEM, are used to explore the impact of resolution on the fidelity of climate simulations.

Generally, SST errors are reduced in HiGEM. Cold SST errors associated with the path of the North Atlantic drift improve, and warm SST errors are reduced in upwelling stratocumulus regions where the simulation of low-level cloud is better at higher resolution. The ocean model in HiGEM allows ocean eddies to be partially resolved, which dramatically improves the representation of sea surface height variability. In the Southern Ocean, most of the heat transports in HiGEM is achieved by resolved eddy motions, which replaces the parameterized eddy heat transport in the lower-resolution model. HiGEM is also able to more realistically simulate small-scale features in the wind stress curl around islands and oceanic SST fronts, which may have implications for oceanic upwelling and ocean biology.

Higher resolution in both the atmosphere and the ocean allows coupling to occur on small spatial scales. In particular, the small-scale interaction recently seen in satellite imagery between the atmosphere and tropical instability waves in the tropical Pacific Ocean is realistically captured in HiGEM. Tropical instability waves play a role in improving the simulation of the mean state of the tropical Pacific, which has important implications for climate variability. In particular, all aspects of the simulation of ENSO (spatial patterns, the time scales at which ENSO occurs, and global teleconnections) are much improved in HiGEM.

Full access
N. L. Miller
,
A. W. King
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M. A. Miller
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E. P. Springer
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M. L. Wesely
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K. E. Bashford
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M. E. Conrad
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K. Costigan
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P. N. Foster
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H. K. Gibbs
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J. Jin
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J. Klazura
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B. M. Lesht
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M. V. Machavaram
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F. Pan
,
J. Song
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D. Troyan
, and
R. A. Washington-Allen

A Department of Energy (DOE) multilaboratory Water Cycle Pilot Study (WCPS) investigated components of the local water budget at the Walnut River watershed in Kansas to study the relative importance of various processes and to determine the feasibility of observational water budget closure. An extensive database of local meteorological time series and land surface characteristics was compiled. Numerical simulations of water budget components were generated and, to the extent possible, validated for three nested domains within the Southern Great Plains—the Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Cloud Atmospheric Radiation Testbed (CART), the Walnut River watershed (WRW), and the Whitewater watershed (WW), in Kansas.

A 2-month intensive observation period (IOP) was conducted to gather extensive observations relevant to specific details of the water budget, including finescale precipitation, streamflow, and soil moisture measurements that were not made routinely by other programs. Event and seasonal water isotope (d18O, dD) sampling in rainwater, streams, soils, lakes, and wells provided a means of tracing sources and sinks within and external to the WW, WRW, and the ARM CART domains. The WCPS measured changes in the leaf area index for several vegetation types, deep groundwater variations at two wells, and meteorological variables at a number of sites in the WRW. Additional activities of the WCPS include code development toward a regional climate model that includes water isotope processes, soil moisture transect measurements, and water-level measurements in groundwater wells.

Full access
J. A. Curry
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P. V. Hobbs
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M. D. King
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D. A. Randall
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P. Minnis
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G. A. Isaac
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J. O. Pinto
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T. Uttal
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A. Bucholtz
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D. G. Cripe
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H. Gerber
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C. W. Fairall
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T. J. Garrett
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J. Hudson
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J. M. Intrieri
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C. Jakob
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T. Jensen
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P. Lawson
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D. Marcotte
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L. Nguyen
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P. Pilewskie
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A. Rangno
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D. C. Rogers
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K. B. Strawbridge
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F. P. J. Valero
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A. G. Williams
, and
D. Wylie

An overview is given of the First ISCCP Regional Experiment Arctic Clouds Experiment that was conducted during April–July 1998. The principal goal of the field experiment was to gather the data needed to examine the impact of arctic clouds on the radiation exchange between the surface, atmosphere, and space, and to study how the surface influences the evolution of boundary layer clouds. The observations will be used to evaluate and improve climate model parameterizations of cloud and radiation processes, satellite remote sensing of cloud and surface characteristics, and understanding of cloud–radiation feedbacks in the Arctic. The experiment utilized four research aircraft that flew over surface-based observational sites in the Arctic Ocean and at Barrow, Alaska. This paper describes the programmatic and scientific objectives of the project, the experimental design (including research platforms and instrumentation), the conditions that were encountered during the field experiment, and some highlights of preliminary observations, modeling, and satellite remote sensing studies.

Full access
J. C. Doran
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S. Abbott
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J. Archuleta
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X. Bian
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J. Chow
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R. L. Coulter
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S. F. J. de Wekker
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S. Edgerton
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S. Elliott
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A. Fernandez
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J. D. Fast
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J. M. Hubbe
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C. King
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D. Langley
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J. Leach
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J. T. Lee
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T. J. Martin
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D. Martinez
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J. L. Martinez
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G. Mercado
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V. Mora
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M. Mulhearn
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J. L. Pena
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R. Petty
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W. Porch
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C. Russell
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R. Salas
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J. D. Shannon
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W. J. Shaw
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G. Sosa
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L. Tellier
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B. Templeman
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J. G. Watson
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R. White
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C. D. Whiteman
, and
D. Wolfe

A boundary layer field experiment in the Mexico City basin during the period 24 February–22 March 1997 is described. A total of six sites were instrumented. At four of the sites, 915-MHz radar wind profilers were deployed and radiosondes were released five times per day. Two of these sites also had sodars collocated with the profilers. Radiosondes were released twice per day at a fifth site to the south of the basin, and rawinsondes were flown from another location to the northeast of the city three times per day. Mixed layers grew to depths of 2500–3500 m, with a rapid period of growth beginning shortly before noon and lasting for several hours. Significant differences between the mixed-layer temperatures in the basin and outside the basin were observed. Three thermally and topographically driven flow patterns were observed that are consistent with previously hypothesized topographical and thermal forcing mechanisms. Despite these features, the circulation patterns in the basin important for the transport and diffusion of air pollutants show less day-to-day regularity than had been anticipated on the basis of Mexico City's tropical location, high altitude and strong insolation, and topographical setting.

Full access
P. N. Vinayachandran
,
Adrian J. Matthews
,
K. Vijay Kumar
,
Alejandra Sanchez-Franks
,
V. Thushara
,
Jenson George
,
V. Vijith
,
Benjamin G. M. Webber
,
Bastien Y. Queste
,
Rajdeep Roy
,
Amit Sarkar
,
Dariusz B. Baranowski
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G. S. Bhat
,
Nicholas P. Klingaman
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Simon C. Peatman
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C. Parida
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Karen J. Heywood
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Robert Hall
,
Brian King
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Elizabeth C. Kent
,
Anoop A. Nayak
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C. P. Neema
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P. Amol
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A. Lotliker
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A. Kankonkar
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D. G. Gracias
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S. Vernekar
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A. C. D’Souza
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G. Valluvan
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Shrikant M. Pargaonkar
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K. Dinesh
,
Jack Giddings
, and
Manoj Joshi

Abstract

The Bay of Bengal (BoB) plays a fundamental role in controlling the weather systems that make up the South Asian summer monsoon system. In particular, the southern BoB has cooler sea surface temperatures (SST) that influence ocean–atmosphere interaction and impact the monsoon. Compared to the southeastern BoB, the southwestern BoB is cooler, more saline, receives much less rain, and is influenced by the summer monsoon current (SMC). To examine the impact of these features on the monsoon, the BoB Boundary Layer Experiment (BoBBLE) was jointly undertaken by India and the United Kingdom during June–July 2016. Physical and biogeochemical observations were made using a conductivity–temperature–depth (CTD) profiler, five ocean gliders, an Oceanscience Underway CTD (uCTD), a vertical microstructure profiler (VMP), two acoustic Doppler current profilers (ADCPs), Argo floats, drifting buoys, meteorological sensors, and upper-air radiosonde balloons. The observations were made along a zonal section at 8°N between 85.3° and 89°E with a 10-day time series at 8°N, 89°E. This paper presents the new observed features of the southern BoB from the BoBBLE field program, supported by satellite data. Key results from the BoBBLE field campaign show the Sri Lanka dome and the SMC in different stages of their seasonal evolution and two freshening events during which salinity decreased in the upper layer, leading to the formation of thick barrier layers. BoBBLE observations were taken during a suppressed phase of the intraseasonal oscillation; they captured in detail the warming of the ocean mixed layer and the preconditioning of the atmosphere to convection.

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

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.

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

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. In Part I, we assessed the meteorological drivers that generated an intense atmospheric river (AR) that caused these record-shattering temperature anomalies. Here, we continue our large collaborative study by analyzing the widespread and diverse impacts driven by the AR landfall. These impacts included widespread rain and surface melt that was recorded along coastal areas, but this was outweighed by widespread high snowfall accumulations resulting in a largely positive surface mass balance contribution to the East Antarctic region. An analysis of the surface energy budget indicated that widespread downward longwave radiation anomalies caused by large cloud-liquid water contents along with some scattered solar radiation produced intense surface warming. Isotope measurements of the moisture were highly elevated, likely imprinting a strong signal for past climate reconstructions. The AR event attenuated cosmic ray measurements at Concordia, something previously never observed. Last, an extratropical cyclone west of the AR landfall likely triggered the final collapse of the critically unstable Conger Ice Shelf while further reducing an already record low sea ice extent.

Significance Statement

Using our diverse collective expertise, we explored the impacts from the March 2022 heat wave and atmospheric river across East Antarctica. One key takeaway is that the Antarctic cryosphere is highly sensitive to meteorological extremes originating from the midlatitudes and subtropics. Despite the large positive temperature anomalies driven from strong downward longwave radiation, this event led to huge amounts of snowfall across the Antarctic interior desert. The isotopes in this snow of warm airmass origin will likely be detectable in future ice cores and potentially distort past climate reconstructions. Even measurements of space activity were affected. Also, the swells generated from this storm helped to trigger the final collapse of an already critically unstable Conger Ice Shelf while further degrading sea ice coverage.

Open access
Peter Bissolli
,
Catherine Ganter
,
Tim Li
,
Ademe Mekonnen
,
Ahira Sánchez-Lugo
,
Eric J. Alfaro
,
Lincoln M. Alves
,
Jorge A. Amador
,
B. Andrade
,
Francisco Argeñalso
,
P. Asgarzadeh
,
Julian Baez
,
Reuben Barakiza
,
M. Yu. Bardin
,
Mikhail Bardin
,
Oliver Bochníček
,
Brandon Bukunt
,
Blanca Calderón
,
Jayaka D. Campbell
,
Elise Chandler
,
Ladislaus Chang’a
,
Vincent Y. S. Cheng
,
Leonardo A. Clarke
,
Kris Correa
,
Catalina Cortés
,
Felipe Costa
,
A.P.M.A. Cunha
,
Mesut Demircan
,
K. R. Dhurmea
,
A. Diawara
,
Sarah Diouf
,
Dashkhuu Dulamsuren
,
M. ElKharrim
,
Jhan-Carlo Espinoza
,
A. Fazl-Kazem
,
Chris Fenimore
,
Steven Fuhrman
,
Karin Gleason
,
Charles “Chip” P. Guard
,
Samson Hagos
,
Mizuki Hanafusa
,
H. R. Hasannezhad
,
Richard R. Heim Jr.
,
Hugo G. Hidalgo
,
J. A. Ijampy
,
Gyo Soon Im
,
Annie C. Joseph
,
G. Jumaux
,
K. R. Kabidi
,
P-H. Kamsu-Tamo
,
John Kennedy
,
Valentina Khan
,
Mai Van Khiem
,
Philemon King’uza
,
Natalia N. Korshunova
,
A. C. Kruger
,
Hoang Phuc Lam
,
Mark A. Lander
,
Waldo Lavado-Casimiro
,
Tsz-Cheung Lee
,
Kinson H. Y. Leung
,
Gregor Macara
,
Jostein Mamen
,
José A. Marengo
,
Charlotte McBride
,
Noelia Misevicius
,
Aurel Moise
,
Jorge Molina-Carpio
,
Natali Mora
,
Awatif E. Mostafa
,
Habiba Mtongori
,
Charles Mutai
,
O. Ndiaye
,
Juan José Nieto
,
Latifa Nyembo
,
Patricia Nying’uro
,
Xiao Pan
,
Reynaldo Pascual Ramírez
,
David Phillips
,
Brad Pugh
,
Madhavan Rajeevan
,
M. L. Rakotonirina
,
Andrea M. Ramos
,
M. Robjhon
,
Camino Rodriguez
,
Guisado Rodriguez
,
Josyane Ronchail
,
Benjamin Rösner
,
Roberto Salinas
,
Hirotaka Sato
,
Hitoshi Sato
,
Amal Sayouri
,
Joseph Sebaziga
,
Serhat Sensoy
,
Sandra Spillane
,
Katja Trachte
,
Gerard van der Schrier
,
F. Sima
,
Adam Smith
,
Jacqueline M. Spence
,
O. P. Sreejith
,
A. K. Srivastava
,
José L. Stella
,
Kimberly A. Stephenson
,
Tannecia S. Stephenson
,
S. Supari
,
Sahar Tajbakhsh-Mosalman
,
Gerard Tamar
,
Michael A. Taylor
,
Asaminew Teshome
,
Wassila M. Thiaw
,
Skie Tobin
,
Adrian R. Trotman
,
Cedric J. Van Meerbeeck
,
A. Vazifeh
,
Shunya Wakamatsu
,
Wei Wang
,
Fei Xin
,
F. Zeng
,
Peiqun Zhang
, and
Zhiwei Zhu
Free access