Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter
Article first published online: 6 MAY 2008
Copyright 2008 by the American Geophysical Union.
Journal of Geophysical Research: Earth Surface (2003–2012)
Volume 113, Issue F2, June 2008
How to Cite
2008), Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter, J. Geophys. Res., 113, F02011, doi:10.1029/2007JF000883., , , and (
- Issue published online: 6 MAY 2008
- Article first published online: 6 MAY 2008
- Manuscript Accepted: 21 FEB 2008
- Manuscript Revised: 16 JAN 2008
- Manuscript Received: 31 JUL 2007
- climate model
 The sensitivity of a global land-surface model projection of near-surface permafrost degradation is assessed with respect to explicit accounting of the thermal and hydrologic properties of soil organic matter and to a deepening of the soil column from 3.5 to 50 or more m. Together these modifications result in substantial improvements in the simulation of near-surface soil temperature in the Community Land Model (CLM). When forced off-line with archived data from a fully coupled Community Climate System Model (CCSM3) simulation of 20th century climate, the revised version of CLM produces a near-surface permafrost extent of 10.7 × 106 km2 (north of 45°N). This extent represents an improvement over the 8.5 × 106 km2 simulated in the standard model and compares reasonably with observed estimates for continuous and discontinuous permafrost area (11.2–13.5 × 106 km2). The total extent in the new model remains lower than observed because of biases in CCSM3 air temperature and/or snow depth. The rate of near-surface permafrost degradation, in response to strong simulated Arctic warming (∼ +7.5°C over Arctic land from 1900 to 2100, A1B greenhouse gas emissions scenario), is slower inthe improved version of CLM, particularly during the early 21st century (81,000 versus 111,000 km2 a−1, where a is years). Even at the depressed rate, however, the warming is enough to drive near-surface permafrost extent sharply down by 2100. Experiments with a deep soil column exhibit a larger increase in ground heat flux than those without because of stronger near-surface vertical soil temperature gradients. This appears to lessen the sensitivity of soil temperature change to model soil depth.