Galton‐Fenzi et al. (2025) Multi-model estimate of Antarctic ice-shelf basal mass budget and ocean drivers

Identification

Journal: The cryosphere
Year: 2025
Date: 2025-12-04
Authors: Benjamin K. Galton‐Fenzi, R Porter-Smith, Sue Cook, Eva A. Cougnon, David E. Gwyther, Wilma G. C. Huneke, Madelaine G. Rosevear, Xylar Asay‐Davis, Fabio Boeira Dias, Michael S. Dinniman, David M. Holland, Kazuya Kusahara, Kaitlin A. Naughten, Keith W. Nicholls, Charles Pelletier, Ole Richter, Hélène Seroussi, Ralph Timmermann
DOI: 10.5194/tc-19-6507-2025

Research Groups

Australian Antarctic Division, Institute for Marine and Antarctic Studies (University of Tasmania), Australian Centre for Excellence in Antarctic Science, Integrated Marine Observing System (Australia)
The University of Queensland (Australia)
Australian National University (Australia)
University of New South Wales (Australia)
Argonne National Laboratory (USA)
Old Dominion University (USA)
New York University (USA)
Thayer School of Engineering, Dartmouth College (USA)
Japan Agency for Marine-Earth Science and Technology (Japan)
British Antarctic Survey (UK)
Earth and Life Institute (UCLouvain, Belgium)
University of Rostock (Germany)
Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (Germany)

Short Summary

This study provides the first multi-model mean estimate of Antarctic ice-shelf basal mass budget and ocean drivers by comparing nine circum-Antarctic ocean simulations, revealing that the multi-model mean melt rate (0.64 m/year) is lower than satellite-derived estimates (0.88 m/year) but highlights the critical, combined influence of thermal driving and friction velocity on melting.

Objective

To compare multiple community-contributed, circum-Antarctic ocean/ice-shelf model simulations to: 1) highlight inter-model differences in basal melt rates, 2) evaluate agreement with satellite-derived melt rates, and 3) examine the underlying physical processes and ocean drivers of Antarctic ice-shelf basal melting.

Study Configuration

Spatial Scale: Circum-Antarctic, covering all Antarctic ice shelves, with detailed analysis for seven major ice shelves (Amery, Fimbul, Larsen C, Ronne-Filchner, Ross, Thwaites, Totten).
Temporal Scale: Model simulations span various periods, generally from the early 1990s to the mid-2010s, with a multi-model mean representative of the early 2000s (median year 2004). Satellite data covers 1994–2018, with a specific product for 2003–2008.

Methodology and Data

Models used: COCO, NEMO (two configurations), FESOM (two resolutions), ROMS (three configurations), E3SM/MPAS-O (total of nine simulations).
Data sources: Satellite altimetry (Adusumilli et al., 2020, for 2003-2008), ICESat, Autonomous phase-sensitive Radio Echo Sounders (ApRES) for future validation, reanalysis products and satellite estimates for sea ice fluxes.

Main Results

The multi-model mean (MMM) estimates an Antarctic ice-shelf basal melt rate of 0.64 m/year, corresponding to a net mass loss of 843 Gt/year (876 Gt/year melting, 33 Gt/year refreezing), with a freeze-to-melt ratio of 3.92 %.
Individual model melt rates range from 0.37 to 0.91 m/year, while satellite-derived estimates indicate a higher mean melt rate of 0.88 m/year (1407 Gt/year melting) and a freeze-to-melt ratio of 18.85 %.
All but one model underpredict the mean melt rate compared to satellite estimates, but the MMM median melt rate is closer to the satellite-inferred median.
A thermo-kinematic melt sensitivity (ζ = m/(T⋆u⋆)) of 4.82 × 10⁻⁵ °C⁻¹ was found for the MMM, demonstrating that both thermal driving (T⋆) and friction velocity (u⋆) are critical, especially near grounding zones.
Models show greater variability in sub-ice salinity distributions compared to current speeds and temperatures, potentially due to differences in sea-ice processes and freshwater fluxes.
The range of thermal melt sensitivities (ψ = m/T⋆) for the MMM is 2.13 to 25.86 m/(°C·year), corresponding to ocean current speeds of 0.028, 0.048, and 0.34 m/s, respectively, highlighting the important role of ocean currents.

Contributions

Provides the first comprehensive multi-model mean (MMM) estimate of circum-Antarctic ice-shelf basal melting, reducing uncertainties associated with single-model outputs.
Quantifies the inter-model spread and discrepancies between model estimates and satellite-derived melt rates, offering insights into potential biases in both.
Introduces and quantifies a thermo-kinematic melt sensitivity (ζ = m/(T⋆u⋆)), emphasizing the critical and roughly equal influence of both thermal driving and friction velocity on melt rates, particularly near grounding zones.
Guides future observational efforts by identifying regions of high model variability and critical melting, fostering better integration of observations and modeling.

Funding

Australian Antarctic Program (Antarctic Gateway Partnership, grant no. SR140300001)
Australian Antarctic Program Partnership (grant no. ASCI000002)
Australian Research Council (ARC) Australian Centre for Excellence in Antarctic Science (grant no. SR200100008)
U.S. National Science Foundation Grant (grant no. OPP-1643652)
NASA Grant (grant no. 80NSSC24K0169)
PARAMOUR project, Fonds de la Recherche Scientifique – FNRS and FWO (Excellence of Science (EOS) program, grant no. O0100718F, EOS ID 30454083)
NASA Cryosphere Science Program (grant no. 80NSSC22K0383)

Citation

@article{GaltonFenzi2025Multimodel,
  author = {Galton‐Fenzi, Benjamin K. and Porter-Smith, R and Cook, Sue and Cougnon, Eva A. and Gwyther, David E. and Huneke, Wilma G. C. and Rosevear, Madelaine G. and Asay‐Davis, Xylar and Dias, Fabio Boeira and Dinniman, Michael S. and Holland, David M. and Kusahara, Kazuya and Naughten, Kaitlin A. and Nicholls, Keith W. and Pelletier, Charles and Richter, Ole and Seroussi, Hélène and Timmermann, Ralph},
  title = {Multi-model estimate of Antarctic ice-shelf basal mass budget and ocean drivers},
  journal = {The cryosphere},
  year = {2025},
  doi = {10.5194/tc-19-6507-2025},
  url = {https://doi.org/10.5194/tc-19-6507-2025}
}

Original Source: https://doi.org/10.5194/tc-19-6507-2025