CLASSIC Archives – PermafrostNet

Parameter optimization for global soil carbon simulations: Not a simple problem

Soils store large amounts of organic carbon that could be released into the atmosphere due to climate change, but future projections from numerical models of soil organic carbon dynamics remain highly uncertain.

A recent study by Charles Gauthier used Bayesian optimization techniques and global sensitivity analysis to better constrain the Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) model’s soil organic carbon parameters.

Getting a handle on how soil stores and releases carbon is critical for modeling climate change, yet global simulations face many challenges due to uncertain parameters and sparse data. The team explored different sets of parameters and tested two types of loss functions, finding that this choice can greatly influence model outcomes.

Schematic representation of the optimization workflow.

The best parameter set resulted in a 12% improvement when compared to observations and matched well with global estimates of soil carbon stocks, particularly at high latitudes. However, the study also points out that certain regions—like the vast needle-leaf forests of Siberia—remain poorly observed and contribute to ongoing uncertainty. By flagging these gaps, the research not only offers a more accurate model but also calls for more targeted data collection and optimization approaches going forward, aiming to close the loop on carbon-climate feedbacks for better future predictions.

Top meter soil organic carbon (SOC) content across the Northern Circumpolar Soil Carbon Database domain obtain with the default parameterization (SDEF) and the two optimized parameter sets (S2EO and SPMO). SOC content is averaged over the 1950–2000 period.

Gauthier, C. B., Melton, J. R., Meyer, G., Raj Deepak, S. N., & Sonnentag, O. (2025). Parameter optimization for global soil carbon simulations: Not a simple problem. Journal of Advances in Modeling Earth Systems, 17, e2024MS004577. https://doi.org/10.1029/2024MS004577

Seminar – 13 November – Modelling the nitrogen cycle of mosses across the boreal forest.

Rose Lefebvre will be presenting Modelling the nitrogen cycle of mosses across the boreal forest.

Date: 13 November 2024
Time: 13:00-14:00 Eastern Time
Location: Zoom (details are posted in our Teams site).

Mosses are common ground cover species in the boreal forest. They can influence different components of the ecosystem, such as the ground thermal regime due to their insulating properties, and the nitrogen cycle through biological nitrogen fixation. Mosses are not always included in terrestrial biosphere models, which are used to make climate projections. The Canadian Land Surface Scheme Including Biogeochemical Cycles (CLASSIC) was modified with the goal of improving productivity simulations across the North American boreal forest. Feather mosses and the nitrogen cycle of mosses were implemented in CLASSIC. The model was validated by comparing observation data against model output at eight sites. The sites range from being near the southern limit of permafrost to being in the continuous permafrost zone. Once validated, the model was run across the North American boreal forest.