Schmidt et al. (2025) Datasets and protocols for including anomalous freshwater from melting ice sheets in climate simulations

Identification

• Journal: Geoscientific model development
• Year: 2025
• Date: 2025-11-07
• Authors: Gavin A. Schmidt, Kenneth D. Mankoff, Jonathan Bamber, Clara Burgard, Dustin Carroll, David Chandler, Violaine Coulon, Benjamin Davison, Matthew H. England, Paul R. Holland, Nicolas C. Jourdain, Qian Li, Juliana M. Marson, Pierre Mathiot, Clive R. McMahon, Twila Moon, Ruth Mottram, Sophie Nowicki, Anna Olivé Abelló, Andrew G. Pauling, Thomas Rackow, Damien Ringeisen
• DOI: 10.5194/gmd-18-8333-2025

Research Groups

• NASA Goddard Institute for Space Studies (USA)
• Autonomic Integra LLC (USA)
• University of Bristol (UK)
• Technical University Munich (Germany)
• Laboratoire d’Océanographie et du Climat Expérimentations et Approches Numériques (LOCEAN), Sorbonne Université, CNRS/IRD/MNHN (France)
• Moss Landing Marine Laboratories, San José State University (USA)
• Jet Propulsion Laboratory, California Institute of Technology (USA)
• NORCE Norwegian Centre, Bjerknes Centre for Climate Research (Norway)
• Université libre de Bruxelles (Belgium)
• University of Sheffield (UK)
• Centre for Marine Science and Innovation (CMSI), University of New South Wales (Australia)
• Australian Centre for Excellence in Antarctic Science (ACEAS), University of New South Wales (Australia)
• British Antarctic Survey (UK)
• Univ. Grenoble Alpes, CNRS, INRAE, IRD, Grenoble INP, IGE (France)
• Massachusetts Institute of Technology (USA)
• Florida State University (USA)
• Centre for Earth Observation Science, University of Manitoba (Canada)
• IMOS Animal Tagging, Sydney Institute of Marine Science (Australia)
• National Snow and Ice Data Center, University of Colorado (USA)
• Danish Meteorological Institute (Denmark)
• University at Buffalo (USA)
• University of Otago (New Zealand)
• European Centre for Medium-Range Weather Forecasts (ECMWF) (Germany)
• Center for Climate Systems Research, Columbia Climate School (USA)
• Canadian Centre for Climate Modelling and Analysis (CCCma), Environment and Climate Change Canada (ECCC) (Canada)

Short Summary

This paper presents comprehensive data products and recommendations for incorporating anomalous freshwater fluxes from the Greenland and Antarctic ice sheets into climate model simulations, particularly for CMIP7, to improve the representation of ocean temperature, sea ice, and regional sea level trends.

Objective

• To provide standardized, observation-based datasets of absolute and anomalous freshwater mass fluxes from the Greenland and Antarctic ice sheets and ice shelves.
• To offer recommendations and protocols for the consistent implementation of these freshwater fluxes in climate model simulations, especially for the Coupled Model Intercomparison Project Phase 7 (CMIP7), to enhance the realism of historical and future climate projections.

Study Configuration

• Spatial Scale: Greenland Ice Sheet (7 basins), Antarctic Ice Sheet (18 basins), surrounding Arctic, North Atlantic, and Southern Oceans. Iceberg melt maps are provided at 0.5° spatial resolution.
• Temporal Scale:
  • Greenland runoff: 1950–2023 (monthly resolution).
  • Greenland ice discharge: 1840–2023 (annual resolution).
  • Antarctic calving: 1997–2021 (annual resolution).
  • Antarctic submarine melt: 1991–2021 (annual resolution).
  • Recommendations cover pre-industrial control, historical (1850–2014), future scenarios (SSP), idealized, Detection and Attribution MIP (DAMIP), and paleoclimate simulations.

Methodology and Data

• Models used:
  • MAR (Modèle Atmosphérique Régional) RCM for Greenland runoff estimates.
  • NEMO (Nucleus for European Modelling of the Ocean) v3.6 and v4.2 with Lagrangian iceberg modules for generating iceberg melt distribution maps.
  • Regional climate models (RCMs) for Antarctic surface mass balance (SMB) estimates.
• Data sources:
  • Satellite observations: GRACE/GRACE-FO for grounded ice mass anomalies, altimetry for ice shelf thinning, remote sensing imagery for iceberg calving.
  • Atmospheric reanalysis: ECMWF Reanalysis project (ERA5) for MAR forcing, JRA55 reanalysis for NEMO forcing.
  • Ice sheet mass balance inter-comparison exercises (IMBIE) for basin definitions and mass change estimates.
  • Surface velocity, ice thickness, and ice density measurements for ice discharge calculations.
  • Firn core analysis for historical Antarctic SMB.
  • BedMachine v3 for ice-shelf draft and bathymetry.

Main Results

• Comprehensive data products are provided for Greenland and Antarctic ice sheets, including runoff, ice discharge, calving, and submarine melt, available at regional (basin) resolution.
• Greenland runoff is estimated from MAR RCM (1950–2023), with an uncertainty of ±15% when averaged over large areas.
• Greenland ice discharge (1840–2023) is computed from surface velocity, ice thickness, and density, with an estimated 50% ± 30% partition between submarine melt and iceberg calving.
• Antarctic calving (1997–2021) and submarine melt (1991–2021) are derived from satellite observations and aggregated by 18 IMBIE regions.
• Spatially explicit iceberg melt maps (0.5° resolution) are generated for both ice sheets, indicating where meltwater is distributed in the ocean.
• The paper highlights that previous CMIP phases' assumptions (fixed discharge or assumed ice sheet mass balance) do not accurately represent observed ice sheet mass loss.
• Detailed recommendations are provided for implementing these freshwater fluxes in CMIP7 experiments, addressing temporal and spatial distribution, energy fluxes (treating additions as ice), and tracer considerations.

Contributions

• This paper delivers the first comprehensive, standardized, and observation-based datasets of anomalous freshwater fluxes from Greenland and Antarctic ice sheets, specifically tailored for climate modeling.
• It provides explicit, multi-tiered guidance and protocols for integrating these fluxes into CMIP7 and other climate simulations, accommodating various model complexities and approaches.
• By enabling the inclusion of observed increasing ice sheet discharge, the work significantly enhances the realism and robustness of climate model simulations for sea surface temperature, sea ice, and regional sea level trends.
• It addresses a critical gap in previous CMIP efforts by moving beyond simplistic ice sheet assumptions, thereby improving the credibility of historical reconstructions and future climate projections.

Funding

• Earth Sciences Division
• NASA Modeling, Analysis and Prediction program (G.A. Schmidt, K.D. Mankoff, Q. Li, D. Ringeisen)
• Agence Nationale de la Recherche – France 2030, PEPR TRACCS programme (grant ANR-22-EXTR-0010) (P. Mathiot, N.C. Jourdain)
• European Commission Horizon 2020 Framework Programme nextGEMS (grant 101003470) (T. Rackow)
• Australian Research Council (ARC Grant Nos. SR200100008, DP190100494) (M.H. England)
• OCEAN ICE (co-funded by European Union Horizon Europe Funding Programme for research and innovation under grant agreement Nr. 101060452 and UK Research and Innovation Internal O:I Contribution number 22) (R. Mottram, P.R. Holland, D.M. Chandler, V. Coulon, N.C. Jourdain, A. Olivé Abelló)
• U.S. National Science Foundation Office of Polar Programs (grant 2052551) (T.A. Moon)
• U.S. National Science Foundation Office of Polar Programs (grant 2052549) (D. Carroll)
• European Union’s Horizon 2020 research and innovation programme, Arctic PASSION (grant 101003472) (J.L. Bamber)
• German Federal Ministry of Education and Research (BMBF), AI4EO (grant 01DD20001) (J.L. Bamber)
• ESA Polar+ Ice Shelves (ESA-IPL-POE-EF-cb-LE-2019-834) (B.J. Davison)
• ESA SO-ICE projects (ESA AO/1-10461/20/I-NB) (B.J. Davison)
• NERC awards NE/T012757/1 (DeCAdeS) and NE/Y006291/1 (NSFGEO-NERC: Investigating the Direct Influence of Meltwater on Antarctic Ice Sheet Dynamics [NSF award number 2053169]) (B.J. Davison)

Citation

@article{Schmidt2025Datasets,
  author = {Schmidt, Gavin A. and Mankoff, Kenneth D. and Bamber, Jonathan and Burgard, Clara and Carroll, Dustin and Chandler, David and Coulon, Violaine and Davison, Benjamin and England, Matthew H. and Holland, Paul R. and Jourdain, Nicolas C. and Li, Qian and Marson, Juliana M. and Mathiot, Pierre and McMahon, Clive R. and Moon, Twila and Mottram, Ruth and Nowicki, Sophie and Abelló, Anna Olivé and Pauling, Andrew G. and Rackow, Thomas and Ringeisen, Damien},
  title = {Datasets and protocols for including anomalous freshwater from melting ice sheets in climate simulations},
  journal = {Geoscientific model development},
  year = {2025},
  doi = {10.5194/gmd-18-8333-2025},
  url = {https://doi.org/10.5194/gmd-18-8333-2025}
}