About

Dr. Marilyn Raphael is a Professor of Geography and the former director of the UCLA Institute of the Environment and Sustainability. Her primary research focus is on Southern Hemisphere atmospheric dynamics and climate change, with major scientific goals including characterizing Antarctic sea ice variability and understanding the interaction between Antarctic sea ice and the large-scale Southern Hemisphere circulation across seasonal, interannual, and decadal time scales. Her work involves global climate modeling with an emphasis on improving the simulation of sea ice and atmospheric processes in the Southern Hemisphere. She is a member of the American Academy of Arts and Sciences, serves as the current Chair of the Scientific Committee on Antarctic Research’s expert group, Antarctic Sea ice Processes and Climate (ASPeCt), and is Co-Chair of the World Climate Research Programme’s (WCRP) Polar Climate Predictability Initiative (PCPI). Dr. Raphael has also served on the National Research Council’s Committees on Future Science Opportunities in Antarctica and the Southern Ocean and on Stabilization Targets for Atmospheric Greenhouse Gas Concentrations. Her educational background includes a B.A. in Geography from McMaster University, an M.A. and Ph.D. in Geography from The Ohio State University. Her research interests encompass Southern Hemisphere atmospheric circulation dynamics, Antarctic sea ice variability and change, global climate modeling, and the Santa Ana Winds of California.

Research topics

• Oceanography
• Environmental science
• Geology
• Climatology
• Atmospheric sciences

Selected publications

• A Geographer at Heart

  2026-02-02

  book-chapter1st authorCorresponding

  In this chapter, the author charts her progress to becoming a geographer beginning in early childhood where an inquisitive mind paired with a fascination for climatic phenomena laid the foundation for a career as a physical geographer. She describes growing up on an island, a former British colony, with a love of books and a single-minded pursuit of knowledge that was geographic without always understanding that it was geography. Answers to her questions about the weather and climate in her high school geography classes spawned even more questions. And being taught human and physical geography at the same time developed her appreciation for the interconnectedness of the world over space and time. The desire to learn more and to be involved in the discovery of knowledge led to study abroad and ultimately to a professorship in geography at UCLA and the presidency of the AAG. In the process, the author recognizes how her experience of geography has helped her to understand her world and its climate.

  PublisherDOI

• Extremes in Southern Hemispheric Zonal Wave‐3 and Their Impact on Antarctic Sea‐Ice Thickness

  Geophysical Research Letters · 2026-03-07

  articleOpen accessSenior author

  Abstract Zonal Wave‐3 (ZW3) is a key zonally asymmetric component of the large‐scale extratropical atmospheric circulation, facilitating mass and energy exchanges between middle and high latitudes in the Southern Hemisphere. Despite the crucial role of sea‐ice thickness (SIT) in modulating sea‐ice volume and climate feedbacks, its response to ZW3 variability remains largely unexplored compared to the more widely studied sea‐ice concentration. Our research identifies variability in the ZW3 pattern and assesses its influence on Antarctic SIT and concentration using a combination of reanalysis and data from a coupled climate model. We project a doubling in the mean frequency of extreme ZW3 events under a high emission scenario, which is likely to contribute to a decline in SIT, primarily through dynamic mechanisms. These extreme events drive mechanical displacement of sea‐ice more than direct thermodynamic melting. Such displacements may expose the underlying ocean, potentially enhancing basal melting through ocean thermal influences.

  PublisherDOI

• Conclusions

  2025-04-08

  book-chapterOpen access

  The diverse chapters in this book have each, and collectively, highlighted how Antarctica and the Southern Ocean are key features on Planet Earth, and how they exert a marked influence on its climate, ecosystems, geopolitics and societies that belies the perception of Antarctica as a wilderness at the end of the world. They also emphasise how susceptible Antarctica is to changes occurring elsewhere across our planet, including biophysical changes that we humans are causing. Recent extreme variations in parts of the Antarctic and Southern Ocean system, and potential tipping points that have distinct global implications, reinforce the requirement to urgently improve our understanding of Antarctic processes. They also emphasise the need for research into their impacts across the planet to be increasingly capable and agile, delivering the evidence needed to inform policy and governance across regional and global scales. This offers the route to help secure the future of Antarctica and the Southern Ocean, and their crucial climatic, biological, societal and cultural benefits, for generations to come.

  PublisherOA PDFDOI

• Supplementary material to "An Assessment of Antarctic Sea-ice Thickness in CMIP6 Simulations with Comparison to the Satellite-based Observations and Reanalyses"

  2025-04-03

  preprintSenior author
  PublisherDOI

• Antarctica and the Southern Ocean

  Bulletin of the American Meteorological Society · 2025-08-01 · 1 citations

  articleOpen access1st authorCorresponding

  In 2024, atmospheric conditions over Antarctica exhibited significant anomalies, and were marked by major surface and stratospheric warming and pressure fluctuations. The first half of the year (January–June) featured persistent below-normal surface pressure over the continent, a distinct zonal wavenumber-3 pattern with three deep atmospheric troughs extending over the Weddell Sea, Prydz Bay, and Ross Ice Shelf, and a positive phase of the Southern Annular Mode, with strong circumpolar westerlies. Surface pressure anomalies in February and April were particularly pronounced, with multiple stations recording record-low pressures. Strong stratospheric warming occurred in July followed by extreme surface warming in August. The surface warming was likely intensified by a compound event: 1) a strong ridge of surface high pressure along coastal East Antarctica advected warm maritime air into the continental interior, and 2) a significant positive geopotential height and temperature anomaly in the stratosphere propagated downward to the surface. As a result, multiple monthly records for high temperatures and pressure were set in August. The Antarctic Ice Sheet’s surface mass balance (SMB) in 2024 was shaped by contrasting periods of high snowfall and regional drought. The most significant anomaly occurred in May, when extreme snowfall led to record-high SMB gains across much of East and West Antarctica. Enhanced meridional moisture transport and atmospheric river events—which funneled moisture from the South Pacific and Atlantic Oceans toward the continent—supported/generated this extreme snowfall. In contrast, September emerged as the driest September on record, with a severe shortage of snowfall over the ice sheet. This was linked to an anomalously deep and eastward-shifted Amundsen Sea Low, which suppressed precipitation and led to below-average SMB across West Antarctica.

  PublisherOA PDFDOI

• Antarctica and the Earth System

  2025-04-08 · 2 citations

  bookOpen accessSenior author

  This book presents a state-of-the-art overview of the role that Antarctica and the Southern Ocean play as integral parts of the Earth System.While often characterised as the last great wilderness on Earth, Antarctica is intimately connected to the rest of the planet, exerting key influences on all places and all people. It is also vulnerable to global changes, especially those driven by humans. This book examines how Antarctica and the Southern Ocean are connected to the rest of the planet, and what these connections mean for the future of Planet Earth and all its inhabitants. It transcends traditional disciplinary boundaries to explore this role across physical, ecological, political, and social systems. Drawing on the latest research findings and thinking, the volume identifies the current leading-order challenges across each of these spheres, highlighting areas where enhanced focus is needed. With the role of Antarctica in the Earth System being one of the most relevant themes of our times, this book will help audiences to understand Antarctica and the Southern Ocean in a global perspective.Antarctica and the Earth System will be of great interest to a wide range of interdisciplinary students and scholars of Earth sciences, Antarctic studies, polar science, and environmental management.The Open Access version of this book, available at http://www.taylorfrancis.com, has been made available under the Creative Commons Attribution (CC-BY) 4.0 license

  PublisherDOI

• An Assessment of Antarctic Sea-ice Thickness in CMIP6 Simulations with Comparison to the Satellite-based Observations and Reanalyses

  2025-04-03 · 1 citations

  preprintOpen accessSenior author

  Abstract. Sea-ice thickness, though critical to our understanding of sea-ice variability, remains relatively understudied compared to surface sea-ice parameters in the Southern Ocean. To remedy this, we examine spatio-temporal variations in sea-ice thickness by analyzing historical simulations from 39 coupled climate models in CMIP6, comparing them with three sea-ice products, including satellite-derived observations and reanalyses. Furthermore, we compare seasonal trends in simulated sea ice thickness with trends in sea ice area. Our results indicate that CMIP6 models can replicate the mean seasonal cycle and spatial patterns of sea-ice thickness. During its maximum in February, these models align well with satellite-based observation products. However, during the annual minima, CMIP6 models show significant agreement with the reanalysis products. Certain models exhibit unrealistic historical mean states compared to the sea-ice products resulting in significant inter-model spread. CMIP6 models can simulate sea-ice area more accurately than the sea-ice thickness. They also simulate a positive relationship between the two parameters in September such that models with greater area tend to exhibit thicker ice. In contrast, there is a negative relationship in February when greater area is associated with lower thickness since only the thicker ice survives the summer melt. Moreover, our study highlights significant positive trends in sea-ice thickness observed during the cooler seasons, which are nearly absent in the warmer seasons where positive trends are predominantly observed in sea-ice area. The spatial distribution of SIT biases is closely linked to uncertainties in modeling the ice edge and the dynamic processes, emphasizing the need for better model representation of both. This study, therefore, highlights the need for improved representation of Antarctic sea-ice processes in models for accurate projections of thickness and related volume changes.

  PublisherOA PDFDOI

• Introduction

  2025-04-08 · 1 citations

  book-chapterOpen access

  Awe-inspiring and culturally unique, Antarctica’s remoteness and extreme conditions have long challenged exploration and understanding. Its vast ice sheet conceals secrets of ancient landscapes and harbours clues to Earth’s past and future. It hosts complex ecosystems and some of the most remarkable lifeforms on our planet. The presence of a giant frozen southern continent shapes all other elements of Earth’s environment and exerts a profound influence on all its life. The connectivity of Antarctica is two-directional, however, and there is increasing evidence that planetary change and human actions are driving significant changes in Antarctica. The purpose of this book is to draw together the latest thinking and understanding of how Antarctica connects to the rest of the planet and shapes our environment, societies, and cultures, and also how our actions are exerting an ever-increasing influence on Antarctica itself. This introduction sets the scene and provides the motivation and context for this examination, which is conducted in detail in the interconnecting chapters that follow.

  PublisherOA PDFDOI

• The 2016 Abrupt Antarctic Sea Ice Decline: A Reevaluation with New Perspectives

  Journal of Climate · 2025-10-27

  article

  Abstract An unprecedented decline in Antarctic sea ice extent (SIE) in late 2016 ended a weak mutidecadal expansion. Multiple mechanisms have been hypothesized to explain this decline, including large-scale atmospheric influences—a strong zonal wave 3 (ZW3) in September 2016 and negative Southern Annular Mode (SAM) in November; oceanic contributions attributed to El Niño–associated surface warming and sustained warm-water upwelling due to intensification of the westerly winds. Given the diversity in hypothesized drivers and several years of anomalously low SIE post-2016 potentially signifying a state change in Antarctic sea ice, we reevaluate likely drivers of the 2016 event. Here, we show that the decline occurred in distinct submonthly episodes from late August to mid-December, with significant variation in synoptic conditions, and that SAM phase transitions, rather than a strong ZW3 preceding a negative SAM, likely explain the magnitude of decline. Oceanic and ice cover preconditioning may also have compounded the sea ice response to atmospheric drivers. Anomalously warm upper ocean during 2016 was associated with early sea ice retreat in the Amundsen–Bellingshausen Seas and Indian Ocean sectors. Moreover, an unusually large open-water area developing in the Weddell Sea from autumn preconditioned that region for rapid heat uptake and SIE decline in warmer months. Finally, we show that record low sea ice cover and broadscale upper-ocean warming during spring/summer point to enhanced radiative surface fluxes and oceanic heat uptake via ice–albedo feedbacks. Lingering effects from upper-ocean warming likely delayed the 2017 growth season onset, with heat potentially being subducted into the subsurface to reemerge in subsequent seasons. Significance Statement Antarctic sea ice extent (SIE) declined dramatically in spring 2016. Multiple explanations of its causes include large-scale atmospheric drivers, El Niño–related upper-ocean warming, and long-term subsurface warming from stronger Southern Ocean winds. Our study shows that SIE decline occurred during several submonthly episodes with varying atmospheric circulations. We show that the transition in the Southern Annular Mode from strongly positive in September to strongly negative in November was important in explaining the magnitude of SIE decline. Interactions between ice cover, overlying atmosphere, and upper ocean likely contributed to the speed and extent of the overall decline in SIE. Significantly reduced sea ice cover by summer may have led to ongoing upper-ocean warming, affecting subsequent sea ice growth.

  PublisherDOI

• An assessment of Antarctic sea-ice thickness in CMIP6 simulations with comparison to the satellite-based observations and reanalyses

  ˜The œcryosphere · 2025-12-12 · 1 citations

  articleOpen accessSenior author

  Abstract. Sea-ice thickness, though critical to our understanding of sea-ice variability, remains relatively understudied compared to surface sea-ice parameters in the Southern Ocean. To remedy this, we examine spatio-temporal variations in sea-ice thickness by analyzing historical simulations from 39 coupled climate models in CMIP6, comparing them with three sea-ice products, including satellite-derived observations and reanalyses. Furthermore, we compare seasonal trends in simulated sea-ice thickness with trends in sea-ice area. Our results indicate that CMIP6 models can replicate the mean seasonal cycle and spatial patterns of sea-ice thickness. During its maximum in February, these models align well with satellite-based observation products. However, during the annual minima, CMIP6 models show significant agreement with the reanalysis products. Certain models exhibit unrealistic historical mean states compared to the sea-ice products resulting in significant inter-model spread. CMIP6 models can simulate sea-ice area more accurately than the sea-ice thickness. They also simulate a positive relationship between the two parameters in September such that models with greater area tend to exhibit thicker ice. In contrast, there is a negative relationship in February when greater area is associated with lower thickness since only the thicker ice survives the summer melt. Moreover, our study highlights significant positive trends in sea-ice thickness observed during the cooler seasons, which are nearly absent in the warmer seasons where positive trends are predominantly observed in sea-ice area. The spatial distribution of SIT biases is closely linked to uncertainties in modeling the ice edge and the dynamic processes, emphasizing the need for better model representation of both. This study, therefore, highlights the need for improved representation of Antarctic sea-ice processes in models for accurate projections of thickness and related volume changes.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Understanding Contemporary Variability in Antarctic Sea Ice: Ensemble Reconstruction of Sea Ice Extent and Concentration for the 20th Century

  NSF · $315k · 2018–2023

• Sensitivity of the South Atlantic Ocean and Climate to Antarctic Sea-Ice Concentration

  NSF · $385k · 2003–2008

Frequent coauthors

• Will Hobbs

  University of Tasmania

  36 shared

• Sharon Stammerjohn

  University of Colorado Boulder

  23 shared

• RA Massom

  Australian Centre for Excellence in Antarctic Science

  17 shared

• Marika M. Holland

  16 shared

• Phillip Reid

  14 shared

• Emmanuel Thibert

  Université Grenoble Alpes

  14 shared

• JL Lieser

  University of Tasmania

  12 shared

• Ryan L. Fogt

  Ohio University

  12 shared

Education

• Ph.D., Geography

  University of California, Los Angeles

  1980

• M.A., Geography

  University of California, Los Angeles

  1976

• B.A., Geography

  University of California, Los Angeles

  1973

Awards & honors

• National Academy of Sciences