Permafrost is a critical component of Earth's climate system and yet many Earth System models do not adequately represent permafrost processes. The complexity of Earth System Models and the pressing need to reduce model spread requires innovative approaches to evaluate and analyze model results. In the Warming in Permafrost Model Intercomparison Project (WrPMIP), we use manipulative field‐based experiments to inform long‐term projections about the magnitude and underlying mechanisms of permafrost carbon dynamics in a changing Arctic. Specifically, we (1) perform and analyze multi-model simulations at the pan-Arctic scale; (2) perform and analyze multi-model simulations at the site-level that align with experimental perturbation approaches; and (3) assess implications of benchmarking for pan-Arctic upscaling and forecasts. Using multi-model simulations from international land modeling groups, we are assessing coherence among models, evaluating model performance against experimental benchmarks, and using the outcomes to inform future measurements.

At the regional scale, we have harmonized output from 14 modeling groups, including two versions of the E3SM land model. The warming simulations entail perturbing model parameters to mimic experimental field trials. Specifically, to mimic open top chamber experiments, aerodynamic resistance in the plant canopy was reduced to capture more heat during the summer, while snow fence experiments were simulated in models by perturbing soil thermal heat conductivity. Across the pan-Arctic, we see contrasting carbon exchange responses to warming geospatially, both in terms of magnitude and relative response of fluxes. Most notably, summer warming produces little response in carbon exchange in most models and winter warming only marginally increases plant carbon uptake over an experimental duration of 20 years. Results will be further analyzed and confronted with experimental observations from the tundra flux database and new benchmarks will be developed.