Calcar et al. (2025) Bedrock uplift reduces Antarctic sea-level contribution over next centuries

Identification

• Journal: Nature Communications
• Year: 2025
• Date: 2025-11-27
• Authors: Caroline van Calcar, Jorge Bernales, Constantijn J. Berends, Wouter van der Wal, Roderik S. W. van de Wal
• DOI: 10.1038/s41467-025-66435-y

Research Groups

• Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands
• Faculty of Aerospace Engineering, Delft University of Technology, Delft, The Netherlands
• Danish Meteorological Institute, Copenhagen, Denmark
• Department of Physical Geography, Utrecht University, Utrecht, The Netherlands
• Royal Netherlands Meteorological Institute, De Bilt, The Netherlands

Short Summary

This study quantifies the impact of heterogeneous solid Earth structure on Antarctic ice sheet retreat and its contribution to barystatic sea-level rise. It finds that including realistic 3D Earth structures in coupled ice-bedrock models delays grounding line retreat by 50 to 130 years and reduces the Antarctic sea-level contribution by 9–23% over the next centuries, an effect that can be twice as large as the uncertainty arising from different climate models.

Objective

• To quantify the stabilising effect of the nonlinear response of multiple 3D Earth structures on the Antarctic Ice Sheet evolution up to the year 2500 under different global warming scenarios (SSP1-2.6 and SSP5-8.5).
• To compare the uncertainty in the choice of climate model with the uncertainties in the Glacial Isostatic Adjustment (GIA) component.
• To assess the impact of 3D Earth structures by comparing sea-level contributions to those using currently employed 1D and ELRA (Elastic Lithosphere Relaxed Asthenosphere) models.
• To quantify the separate contributions of bedrock deformation and local sea-level fall due to self-gravitation.

Study Configuration

• Spatial Scale: Antarctic Ice Sheet (West and East Antarctica, with focus on Amundsen Sea Embayment, Weddell Sea, Ross Ice Shelf, Wilkes Subglacial Basin). Ice sheet model grid resolution: 16 kilometers. GIA model global resolution: 200 kilometers, with a higher resolution region of 30 kilometers over Antarctica.
• Temporal Scale: Centennial to multi-centennial (500 years), from present day up to 2500.

Methodology and Data

• Models used:
  • Coupled ice-sheet – 3D GIA model.
  • Ice sheet model: IMAU-ICE (version 2.0), combining shallow ice and shallow shelf approximations.
  • GIA model: Spherical finite element (FE) model, materially compressible, capable of including self-gravity (though self-gravity in GIA model was excluded in main simulations for computational efficiency).
  • Comparison models: Rigid Earth, 1D Earth structure (100 km elastic lithosphere, 10^21 Pa·s upper mantle viscosity), and ELRA model (relaxation timescale of 3000 years).
• Data sources:
  • Present-day ice and bedrock topography: Bedmachine version 3.
  • Surface mass balance: Temperature and radiation parameterisation.
  • Geothermal heat flux: Shapiro and Ritzwoller (2004).
  • Basal melt at ice shelf: Favier quadratic method.
  • Initial ocean temperature and salinity: World Ocean Atlas 2018.
  • Initial atmospheric temperature and precipitation: ERA5 reanalysis.
  • Forcing scenarios (ocean temperature, salinity, atmospheric temperature anomalies, precipitation ratios): Products from CESM2-WACCM (CESM) and IPSL-CM6A-LR (IPSL) climate models for IPCC scenarios SSP1-2.6 (low emission) and SSP5-8.5 (high emission).
  • 3D Earth structure (mantle rheology): Spatially varying seismic velocity anomalies from Lloyd et al. (2019) for Antarctica and Becker and Boschi (2002) globally, converted to mantle temperature and then to dislocation and diffusion parameters based on olivine flow laws. Constrained by regional viscosity estimates from GPS data in Amundsen Sea Embayment, Weddell Sea Embayment, and Palmer Land. Two 3D structures (3D Weaker and 3D Stronger) were derived by varying grain size and water content.

Main Results

• The inclusion of heterogeneous solid Earth structures (3D models) delays grounding line retreat by 50 to 130 years compared to rigid Earth models.
• The barystatic sea-level contribution from the Antarctic Ice Sheet is reduced by 9–23% (0.7–1.3 meters) by 2500 when using 3D Earth structures compared to a rigid Earth.
• The stabilising effect of the solid Earth feedback can be up to twice as large as the uncertainty arising from differences between climate models (e.g., 23% reduction from 3D Weaker vs. 16% difference between climate models).
• The 3D Weaker Earth structure leads to a sea-level rise reduction of up to 23% (approximately 1 meter) by 2500 compared to a rigid Earth. The 3D Stronger structure reduces sea-level rise by up to 14%.
• Simplified 1D Earth structures and ELRA models systematically underestimate the stabilising effect, showing only a 2–5% reduction in sea-level rise.
• The primary mechanism for stabilisation is the reduction of ice shelf area growth due to delayed grounding line retreat, which in turn decreases basal mass loss.
• The impact of 3D Earth structures is more significant under low emission scenarios (SSP1-2.6), leading to delays of up to 130 years. Under high emission scenarios (SSP5-8.5), the delay is smaller (20–30 years) because bedrock uplift cannot keep pace with rapid ice loss, leading to eventual West Antarctic Ice Sheet collapse regardless of Earth structure.
• Bedrock uplift is the main stabilising factor; local sea-level drop due to self-gravitation is a smaller, secondary effect (e.g., local sea-level drop of 8 meters vs. bedrock uplift of hundreds of meters by 2500).

Contributions

• First study to quantify the impact of bedrock deformation relative to the uncertainty introduced by different climate models in Antarctic sea-level projections.
• Integration of a 3D Glacial Isostatic Adjustment (GIA) model with nonlinear mantle rheology into an ice sheet model, providing a more realistic representation of Earth-ice interactions compared to traditional simplified models (rigid Earth, ELRA, 1D).
• Evaluation of the sensitivity of Antarctic Ice Sheet evolution to Earth structure under the latest Shared Socioeconomic Pathways (SSP) scenarios.
• Isolation and quantification of the separate contributions of bedrock deformation and local sea-level fall due to self-gravitation to the overall stabilising effect.
• Emphasises the critical need to consider realistic, heterogeneous Earth structures for accurate centennial-scale projections of Antarctic sea-level contribution.

Funding

• European Union’s Horizon 2020 Research and Innovation Programme (PROTECT project, grant agreement No 869304)
• ESA Support to Science Element (STSE) (3D Earth project)
• NWO (grant OCENW.KLEIN.515)

Citation

@article{Calcar2025Bedrock,
  author = {Calcar, Caroline van and Bernales, Jorge and Berends, Constantijn J. and Wal, Wouter van der and Wal, Roderik S. W. van de},
  title = {Bedrock uplift reduces Antarctic sea-level contribution over next centuries},
  journal = {Nature Communications},
  year = {2025},
  doi = {10.1038/s41467-025-66435-y},
  url = {https://doi.org/10.1038/s41467-025-66435-y}
}