Shaw et al. (2025) Mountain glaciers recouple to atmospheric warming over the twenty-first century

Identification

• Journal: Nature Climate Change
• Year: 2025
• Date: 2025-10-10
• Authors: Thomas E. Shaw, Evan Miles, Michael McCarthy, Pascal Buri, Nicolas Guyennon, Franco Salerno, Luca Carturan, Ben Brock, Francesca Pellicciotti
• DOI: 10.1038/s41558-025-02449-0

Research Groups

• Institute of Science and Technology Austria, Klosterneuburg, Austria
• Swiss Federal Institute WSL, Birmensdorf, Switzerland
• Department of Geography: Glaciology and Geomorphodynamics, University of Zürich, Zurich, Switzerland
• Department of Geosciences, University of Fribourg, Fribourg, Switzerland
• Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, USA
• National Research Council, Water Research Institute (IRSA-CNR), Rome, Italy
• National Research Council, Institute of Polar Sciences (ISP-CNR), Milan, Italy
• Department of Land, Environment, Agriculture and Forestry, University of Padova, Padova, Italy
• Department of Geography and Environmental Sciences, Northumbria University, Newcastle, UK

Short Summary

This study assesses how temperature decoupling over mountain glaciers changes under warming, finding that local cooling is maximized in the 2020s-2030s before widespread glacier retreat leads to a recoupling of glacier air temperatures with their surroundings, increasing their sensitivity to warming.

Objective

• To assess the extent to which the relationship between on-glacier and ambient air temperatures (temperature decoupling) changes under future warming scenarios, and to identify the factors controlling its magnitude and evolution globally.

Study Configuration

• Spatial Scale: Global, covering 186,792 mountain glaciers from the Randolph Glacier Inventory (RGI) v.6, excluding ice caps, ice sheets, and large periphery glaciers of Greenland and Antarctica.
• Temporal Scale:
  • Observational data: 1994–2023.
  • Recent past climatology: 2000–2022.
  • Future projections: 2000–2099.

Methodology and Data

• Models used:
  • Statistical model: Multilinear regression model (optimized with lasso regressor) to estimate the temperature decoupling factor (k).
  • Climate models: Ensemble mean of six CMIP6 models (AWI-CM-1-1-MR, CMCC-CM2-SR5, CanESM5-CanOE, INM-CM5-0, KIOST-ESM, NESM3) for Shared Socioeconomic Pathways (SSP) 2-4.5 and 5-8.5.
  • Glacier change estimates: Published estimates of glacier area and thickness change (Rounce et al., 2023).
• Data sources:
  • Observational data: Compilation of 3.7 million hourly meteorological observations from 350 on-glacier automatic weather stations (AWS) spanning 62 glaciers in 169 individual summer seasons.
  • Reanalysis data: ERA5-Land (air temperature, dewpoint temperature, 10-m wind speed, specific humidity, incoming shortwave/longwave radiation).
  • Glacier inventory: Randolph Glacier Inventory (RGI) v.6.
  • Debris cover: Global assessment of supraglacial debris-cover extents (Scherler et al., 2018).
  • Topographic data: 30-meter ASTER Digital Elevation Model (DEM).
  • Snow cover and albedo: MODIS MOD10A1.

Main Results

• Currently, glacier boundary layers warm approximately 0.83 °C on average for every 1 °C ambient temperature rise (global mean k = 0.83 [95% CI 0.80, 0.85] for 2000–2022).
• The mean cooling relative to ambient temperature is -0.40 °C [95% CI -0.47, -0.37] globally for 2000–2022.
• Temperature decoupling and associated relative cooling over glaciers are projected to be maximized globally between the late 2020s and late 2040s, with regional variations.
• Beyond mid-century, widespread glacier retreat, particularly under SSP 5-8.5, leads to a significant reduction in the glacier boundary layer effect, causing above-glacier air temperatures to 'recouple' with their surroundings.
• By 2099, approximately 68% of the analyzed glaciers are projected to be lost under SSP 2-4.5, and 84% under SSP 5-8.5.
• Surviving glaciers by the end of the century (2080–2099) will exhibit a mean k of 0.92 [95% CI 0.91, 0.93] under SSP 2-4.5 and 0.96 [95% CI 0.95, 0.97] under SSP 5-8.5, resulting in significantly less cooling (-0.31 °C and -0.17 °C, respectively).
• The magnitude of decoupling is primarily controlled by off-glacier air temperature, specific humidity, glacier flowpath distance, elevation, and synoptic wind speed. The presence of debris cover also significantly promotes recoupling.

Contributions

• Provides the first global assessment of temperature decoupling on mountain glaciers and its projected evolution throughout the 21st century under different climate change scenarios.
• Highlights the nonlinear feedback mechanism of glacier microclimates to atmospheric warming, challenging the linear response assumptions often used in glaciohydrological models.
• Offers a dynamic parameterization for glacier cooling that can improve future modeling efforts for regional water resources and glacier-related hazards.
• Compiles and analyzes an unprecedentedly large dataset of on-glacier meteorological observations from around the world.

Funding

• EU Horizon 2020 Marie Skłodowska-Curie Actions grant 101026058
• EU Horizon 2020 Marie Skłodowska-Curie grant agreement no. 101034413
• European Research Council under the European Union’s Horizon 2020 research and innovation programme grant agreement no. 772751 (RAVEN project)
• Swiss National Science Foundation (ASCENT Project 189890)
• European Union Next-Generation EU (National Recovery and Resilience Plan—NRRP, Mission 4, Component 2, Investment 1.3—D.D. 1243 2/8/2022, PE0000005) (RETURN Extended Partnership)

Citation

@article{Shaw2025Mountain,
  author = {Shaw, Thomas E. and Miles, Evan and McCarthy, Michael and Buri, Pascal and Guyennon, Nicolas and Salerno, Franco and Carturan, Luca and Brock, Ben and Pellicciotti, Francesca},
  title = {Mountain glaciers recouple to atmospheric warming over the twenty-first century},
  journal = {Nature Climate Change},
  year = {2025},
  doi = {10.1038/s41558-025-02449-0},
  url = {https://doi.org/10.1038/s41558-025-02449-0}
}