Comparison of effects of cold‐region soil/snow processes and the uncertainties from model forcing data on permafrost physical characteristics

• Published in: Journal of advances in modeling earth systems Vol. 8; no. 1; pp. 453 - 466
• Main Authors: Barman, Rahul, Jain, Atul K.
• Format: Journal Article
• Language: English
• Published: Washington John Wiley & Sons, Inc 01.03.2016; American Geophysical Union (AGU)
• Subjects: Air temperature; Biogeochemistry; biogeophysics; Climatic data; Cold; Cold effects; Compaction; Datasets; Depth hoar; Depth hoar formation; Energy; energy cycle; GEOSCIENCES; Heat conductivity; Hydrology; Land cover; Land surface models; Meteorology; Modelling; Organic carbon; Permafrost; permafrost area; permafrost degradation; Physics; Root zone; Snow; Soil columns; Soil properties; Soil temperature; Stability; Studies; Temperature differences; water cycle; Wind
• ISSN: 1942-2466; 1942-2466
• DOI: 10.1002/2015MS000504

We used a land surface model to (1) evaluate the influence of recent improvements in modeling cold‐region soil/snow physics on near‐surface permafrost physical characteristics (within 0–3 m soil column) in the northern high latitudes (NHL) and (2) compare them with uncertainties from climate and land‐cover data sets. Specifically, four soil/snow processes are investigated: deep soil energetics, soil organic carbon (SOC) effects on soil properties, wind compaction of snow, and depth hoar formation. In the model, together they increased the contemporary NHL permafrost area by 9.2 × 106 km2 (from 2.9 to 12.3—without and with these processes, respectively) and reduced historical degradation rates. In comparison, permafrost area using different climate data sets (with annual air temperature difference of ∼0.5°C) differed by up to 2.3 × 106 km2, with minimal contribution of up to 0.7 × 106 km2 from substantial land‐cover differences. Individually, the strongest role in permafrost increase was from deep soil energetics, followed by contributions from SOC and wind compaction, while depth hoar decreased permafrost. The respective contribution on 0–3 m permafrost stability also followed a similar pattern. However, soil temperature and moisture within vegetation root zone (∼0–1 m), which strongly influence soil biogeochemistry, were only affected by the latter three processes. The ecosystem energy and water fluxes were impacted the least due to these soil/snow processes. While it is evident that simulated permafrost physical characteristics benefit from detailed treatment of cold‐region biogeophysical processes, we argue that these should also lead to integrated improvements in modeling of biogeochemistry. Key Points: Soil/snow affect permafrost area, degradation much stronger than climate/land‐cover differences Strongest role of deep soils on permafrost area, degradation but low impact in root zone states Energy/water fluxes are impacted more by climate/land‐cover differences than soil/snow changes