Brivoal et al. (2025) Implementation of an intermediate-complexity snow-physics scheme (ISBA-Explicit Snow) into a sea ice model (SI ³ ): 1D thermodynamic coupling and validation

Identification

• Journal: Geoscientific model development
• Year: 2025
• Date: 2025-10-07
• Authors: Théo Brivoal, Virginie Guémas, Martin Vancoppenolle, Clément Rousset, Bertrand Decharme
• DOI: 10.5194/gmd-18-6885-2025

Research Groups

• Centre National de Recherches Météorologiques (CNRM), Météo-France, CNRS, Université de Toulouse, Toulouse, France
• LOCEAN-IPSL, CNRS, Sorbonne Université, Paris, France

Short Summary

This study implements an intermediate-complexity snow-physics scheme (ISBA-Explicit Snow) into the SI3 sea ice model, validating its 1D thermodynamic coupling against observations and another advanced snow model. The coupled model realistically simulates dynamic snow properties, leading to more accurate snow-ice interface temperatures and heat transfer compared to simpler schemes.

Objective

• To implement and validate an intermediate-complexity snow-physics scheme (ISBA-Explicit Snow) into the SI3 sea ice model, focusing on 1D thermodynamic processes, to improve the representation of snow cover over sea ice for future climate models.

Study Configuration

• Spatial Scale: Unidimensional (1D vertical) simulations following a Lagrangian trajectory (SHEBA tower path).
• Temporal Scale: November 1997 to September 1998 (during the SHEBA experiment).

Methodology and Data

• Models used:
  • SI3 (Sea Ice modeling Integrated Initiative, part of NEMO 4.2.2)
  • ISBA-Explicit Snow (ISBA-ES)
  • SnowModel-LG (for comparison and validation)
• Data sources:
  • Surface Heat Budget of the Arctic Ocean (SHEBA) experiment (in situ observations of snow thickness, surface temperature, snow-ice interface temperature, and albedo).
  • NASA’s Modern Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) (atmospheric forcing).
  • European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric data (ERA5) (atmospheric forcing).
  • GLORYS12 reanalysis (oceanic forcing).
  • SnowModel-LG outputs (for comparison).

Main Results

• The SI3+ISBA-ES model simulates realistic snow thicknesses, densities, and temperatures, aligning well with SHEBA observations and SnowModel-LG outputs, and captures their temporal variability.
• Unlike the previous SI3 snow scheme (constant density and thermal conductivity), the coupled model realistically simulates the temporal evolution of snow bulk density and thermal conductivity.
• This dynamic representation results in more accurate temperatures at the snow-ice interface and a more realistic heat transfer between the underlying sea ice and the atmosphere.
• Snowpack thickness, density, and thermal conductivity are significantly sensitive to parameterization choices for snowfall density and wind-induced snow compaction, as well as to the choice of atmospheric forcing.
• ISBA-ES simulations produce thinner sea ice (mean 2.17 m to 2.26 m) compared to the SI3-only simulation (2.36 m), but better reproduce the timing of melt onset. The observed mean sea ice thickness was 2.38 m.
• The default ISBA-ES snowdrift parameterization (Brun et al., 1997) increases near-surface density but may underestimate the density of Arctic wind slab layers (maximum density 350 kg/m³ compared to observed 403 kg/m³). The Royer et al. (2021) parameterization (maximum 600 kg/m³) allows for higher densities, potentially better representing wind slabs, though it may lead to a slightly overly dense snowpack.
• Snow thermal conductivity in ISBA-ES simulations ranges from 0.10 W/(m·K) to 0.14 W/(m·K) during the accumulation period, which is lower than the constant 0.31 W/(m·K) used in SI3, leading to increased insulation and warmer, thinner ice.
• The model tends to overestimate the albedo decrease during the melt season, leading to a rapid snowmelt compared to observations.

Contributions

• First-time implementation of an intermediate-complexity snow-physics scheme (ISBA-Explicit Snow) into a global sea ice model (SI3) designed for global to regional applications.
• Demonstrates the critical importance of modeling temporal changes in snow layer density and thermal conductivity for accurate snow-ice interface temperatures and heat transfer in sea ice models.
• Highlights the significant sensitivity of simulated snowpack properties and sea ice thermodynamics to the choice of snowfall density and wind compaction parameterizations, as well as atmospheric forcing.
• Provides a physically consistent response of sea ice thickness to improved snow physics, laying the groundwork for full integration into the CNRM-CM climate model.

Funding

• Agence Nationale de la Recherche (Investissement d’Avenir program, ANR-17-MPGA-0003 ASET reference)
• European Union’s Horizon 2020 research and innovation program (grant agreement no. 101003826, project CRiceS)

Citation

@article{Brivoal2025Implementation,
  author = {Brivoal, Théo and Guémas, Virginie and Vancoppenolle, Martin and Rousset, Clément and Decharme, Bertrand},
  title = {Implementation of an intermediate-complexity snow-physics scheme (ISBA-Explicit Snow) into a sea ice model (SI <sup>3</sup> ): 1D thermodynamic coupling and validation},
  journal = {Geoscientific model development},
  year = {2025},
  doi = {10.5194/gmd-18-6885-2025},
  url = {https://doi.org/10.5194/gmd-18-6885-2025}
}