Sensitivity of a model projection of near‐surface permafrost degradation to soil column depth and representation of soil organic matter

作者：David M. Lawrence, Andrew G. Slater, V. E. Romanovsky, Dmitry J. Nicolsky · 发表于：Journal of Geophysical Research Atmospheres · 年份：2008 · DOI：10.1029/2007jf000883 · 被引用次数：349 · 研究领域：Climate change and permafrost、Cryospheric studies and observations、Arctic and Antarctic ice dynamics

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 ...