Diverging runoff drives uncertainty in Antarctic surface mass balance projections under a high emission scenario
- 1Institut des Géosciences de l'Environnement (Saint-Martin-d'Hères, France)
- 2Université Grenoble Alpes (Saint-Martin-d'Hères, France)
- 3Centre National de la Recherche Scientifique (Paris, France)
Abstract
Antarctic surface mass balance (SMB) projections are a major source of uncertainty in future sea-level rise estimates, and regional climate models (RCMs), thanks to their finer resolution and polar-tailored physics, are increasingly used to refine and complement Earth System Model (ESM) projections. Here, three recent downscalings of the ESM CESM2 with the RCMs MAR, RACMO, and HIRHAM under SSP5-8.5 produce consistent contemporary Antarctic SMB, but diverge strongly by 2100, especially over ice shelves. Projected SMB anomalies there range from a large decline in HIRHAM to a moderate decrease in MAR, while RACMO maintains near balance. These differences mainly reflect contrasting melt–albedo feedbacks and present-day melt and refreezing levels, particularly in HIRHAM, where melt and refreezing rates are about five and four times higher than both MAR and RACMO, reaching levels the other two models only attain by the end of the century, along with a persistent 1–2 °C temperature offset between MAR and RACMO. CESM2 shows a decline similar in magnitude to MAR, with high melt partly compensated by extensive refreezing. Over grounded ice, all models project increased SMB from higher snowfall, though runoff still drives their SMB spread. Despite identical boundary conditions and similar present-day SMB, the four models diverge substantially by 2100. Yet CESM2, despite its coarser resolution as an ESM, reproduces integrated behavior consistent with MAR. These results show that inter-model agreement on present-day SMB does not guarantee reliable future projections, underscoring the need for continued RCM development to better constrain the Antarctic contribution to sea-level rise.
Versions
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BibTeX
@article{heurgue2026diverging,
title = {{Diverging runoff drives uncertainty in Antarctic surface mass balance projections under a high emission scenario}},
author = {Benjamin Heurgue and Charles Amory and Christoph Kittel and Fredrik Boberg and Gaël Durand and Vincent Favier and Xavier Fettweis and Quentin Glaude and Heiko Goelzer and Nicolaj Hansen and Nicolas C. Jourdain and Ruth Mottram and Martin Olesen and Willem Jan Van de Berg and Michiel R. Van den Broeke and René R. Wijngaard},
journal = {The Cryosphere},
year = {2026},
month = nov,
doi = {10.5194/tc-20-6353-2026},
url = {https://doi.org/10.5194/tc-20-6353-2026},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Diverging runoff drives uncertainty in Antarctic surface mass balance projections under a high emission scenario
AU - Benjamin Heurgue
AU - Charles Amory
AU - Christoph Kittel
AU - Fredrik Boberg
AU - Gaël Durand
AU - Vincent Favier
AU - Xavier Fettweis
AU - Quentin Glaude
AU - Heiko Goelzer
AU - Nicolaj Hansen
AU - Nicolas C. Jourdain
AU - Ruth Mottram
AU - Martin Olesen
AU - Willem Jan Van de Berg
AU - Michiel R. Van den Broeke
AU - René R. Wijngaard
PY - 2026
DA - 2026/11/09
JO - The Cryosphere
DO - 10.5194/tc-20-6353-2026
UR - https://doi.org/10.5194/tc-20-6353-2026
AB - Antarctic surface mass balance (SMB) projections are a major source of uncertainty in future sea-level rise estimates, and regional climate models (RCMs), thanks to their finer resolution and polar-tailored physics, are increasingly used to refine and complement Earth System Model (ESM) projections. Here, three recent downscalings of the ESM CESM2 with the RCMs MAR, RACMO, and HIRHAM under SSP5-8.5 produce consistent contemporary Antarctic SMB, but diverge strongly by 2100, especially over ice shelves. Projected SMB anomalies there range from a large decline in HIRHAM to a moderate decrease in MAR, while RACMO maintains near balance. These differences mainly reflect contrasting melt–albedo feedbacks and present-day melt and refreezing levels, particularly in HIRHAM, where melt and refreezing rates are about five and four times higher than both MAR and RACMO, reaching levels the other two models only attain by the end of the century, along with a persistent 1–2 °C temperature offset between MAR and RACMO. CESM2 shows a decline similar in magnitude to MAR, with high melt partly compensated by extensive refreezing. Over grounded ice, all models project increased SMB from higher snowfall, though runoff still drives their SMB spread. Despite identical boundary conditions and similar present-day SMB, the four models diverge substantially by 2100. Yet CESM2, despite its coarser resolution as an ESM, reproduces integrated behavior consistent with MAR. These results show that inter-model agreement on present-day SMB does not guarantee reliable future projections, underscoring the need for continued RCM development to better constrain the Antarctic contribution to sea-level rise.
SN - 1994-0424
ER -