Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter
Sensitivity of a model projection of near-surface permafrost degradation to soil column depth and representation of soil organic matter
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DOI：
10.1029/2007jf000883
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发表时间：
2008-05-06
影响因子：
3.9
通讯作者：
Nicolsky, Dmitry J.
中科院分区：
文献类型：
--
作者：
Lawrence, David M.;Slater, Andrew G.;Nicolsky, Dmitry J.
近地表多年冻土退化的全球陆面模型预测的敏感性进行了评估，明确会计土壤有机质的热和水文特性和加深的土柱从3.5到50米或更多。这些修改导致社区土地模型（CLM）中近地表土壤温度的模拟有了很大的改进。当与完全耦合的社区气候系统模式（CCSM 3）模拟20世纪世纪气候的存档数据被迫离线时，CLM的修订版产生了10.7 x 10（6）km（2）（北纬45度以北）的近地表永久冻土范围。这一范围比标准模型模拟的8.5 x 10（6）km（2）有所改善，并与连续和不连续永久冻土区的观测估计值（11.2-13.5 x 10（6）km（2））进行了合理比较。由于CCSM 3气温和/或雪深的偏差，新模型的总范围仍然低于观测值。近地表永久冻土退化的速度，响应强烈的模拟北极变暖（类似于从1900年到2100年北极陆地上的+7.5摄氏度，A1 B温室气体排放情景），在CLM的改进版本中较慢，特别是在21世纪初（81，000对111，000 km（2）a（-1），其中a是年）。然而，即使是在降低的速度下，变暖也足以在2100年前使近地表的永久冻土范围急剧下降。由于近地表垂直土壤温度梯度较强，深土柱实验中的土壤热通量比无深土柱实验中的土壤热通量有较大的增加。这似乎降低了土壤温度变化对模型土壤深度的敏感性。
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 x 10(6) km(2) (north of 45 degrees N). This extent represents an improvement over the 8.5 x 10(6) km(2) simulated in the standard model and compares reasonably with observed estimates for continuous and discontinuous permafrost area (11.2-13.5 x 10(6) km(2)). 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 (similar to +7.5 degrees C over Arctic land from 1900 to 2100, A1B greenhouse gas emissions scenario), is slower in the improved version of CLM, particularly during the early 21st century (81,000 versus 111,000 km(2) 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.