Preprints
https://doi.org/10.5194/egusphere-2024-1778
https://doi.org/10.5194/egusphere-2024-1778
21 Jun 2024
 | 21 Jun 2024
Status: this preprint is open for discussion.

Inter-model differences in 21st Century Glacier Runoff for the World’s Major River Basins

Finn Wimberly, Lizz Ultee, Lilian Schuster, Matthias Huss, David R. Rounce, Fabien Maussion, Sloan Coats, Jonathan Mackay, and Erik Holmgren

Abstract. Projected glacier change has important downstream consequences, including sea level rise, changing freshwater supply, and loss of important cultural sites. While the glacier contribution to global sea level rise and associated uncertainties have been quantified in model intercomparison studies, comparatively less focus has been directed towards the inter-annual changes in runoff caused by glacier recession. The observed effect of glacier runoff on basin-level water availability makes simulated future runoff a particularly consequential target for analysis. In this study, we compare century-scale runoff simulated by three global glacier evolution models. Aggregating annual glacier runoff contributions to 75 globally-distributed major river basins, we find that the three models agree closely in some basins but differ dramatically (up to a factor of 3.8) in others. However, when we analyze century-scale runoff changes relative to a glacier model's historical runoff baseline, annual runoff projections are much more consistent across glacier models. Glacier models project broadly consistent relative changes in seasonal runoff supply, with some differences across climatic regions. Estimates of the year of peak water are more consistent across glacier models (when driven by a climate model ensemble) than across individual climate forcings within a single glacier model. We identify the glacier models' different approaches to modifying precipitation forcing as the dominant source of inter-model differences in projected runoff. Our findings highlight the comparative roles of glacier evolution model, global climate model forcing, and emissions scenario as important sources of uncertainty across different metrics of projected glacier runoff. We recommend steps to account for glacier model uncertainties in glacio-hydrological modelling efforts.

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Finn Wimberly, Lizz Ultee, Lilian Schuster, Matthias Huss, David R. Rounce, Fabien Maussion, Sloan Coats, Jonathan Mackay, and Erik Holmgren

Status: open (until 28 Aug 2024)

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Finn Wimberly, Lizz Ultee, Lilian Schuster, Matthias Huss, David R. Rounce, Fabien Maussion, Sloan Coats, Jonathan Mackay, and Erik Holmgren

Model code and software

Runoff Processing Notebooks Finn Wimberly and Lizz Ultee https://github.com/finnwimberly/glacial_runoff_intercomparison

Finn Wimberly, Lizz Ultee, Lilian Schuster, Matthias Huss, David R. Rounce, Fabien Maussion, Sloan Coats, Jonathan Mackay, and Erik Holmgren

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Short summary
Glacier models have historically been used to understand glacier melt’s contribution to sea level rise. The capacity to project seasonal glacier runoff is a relatively recent development for these models. In this study we provide the first model intercomparison of runoff projections for the glacier evolution models capable of simulating future runoff globally. We compare model projections from 2000 to 2100 for all major river basins larger than 3000 km2 with over 1 % of initial glacier cover.