黄河源区多年冻土空间分布变化特征数值模拟

基于IPCC第五次评估报告预估的气温变化情景,采用数值模拟的方法对黄河源区典型冻土类型开展模拟,推算过去及预测未来黄河源区冻土分布空间变化过程和发展趋势。结果表明：1972-2012年源区多年冻土只有少部分发生退化,退化的冻土面积为833 km²,季节冻土主要集中在源区东南部的热曲谷地、小野马岭以及两湖流域南部的汤岔玛地带;RCP 2.6、RCP 6.0、RCP 8.5情景下,2050年多年冻土退化为季节冻土的面积差别不大,分别为2224 km²、2347 km²、2559 km²,占源区面积的7.5%、7.9%、8.6%;勒那曲、多曲、白马曲零星出现季节冻土,野牛沟、野马滩以及鄂陵湖东部的玛多四湖所在黄河低谷大片为季节冻土;2100年多年冻土退化为季节冻土的面积分别为5636 km²、9769 km²、15548 km²,占源区面积的19%、32.9%、52.3%;星宿海、尕玛勒滩、多格茸的多年冻土发生退化,低温冻土变为高温冻土,各类年平均地温出现了不同程度的升高。到2100年,RCP 2.6情景下源区多年冻土全部退化为季节冻土主要发生在目前年平均地温高于-0.15 oC的区域,而-0.15~-0.44 oC的区域部分发生退化;RCP 6.0、RCP 8.5情景下目前年平均地温分别为高于-0.21 oC以及-0.38o C的区域多年冻土全部发生退化,而-0.21~-0.69 oC以及-0.38~-0.88 oC的区域部分发生退化。

Numerical simulation of spatial distribution and change of permafrost in the source area of the Yellow River

The numerical simulation method was used to predict the future possible changes that happened on permafrost by setting up the prediction results of the climate model from the IPCC Fifth Assessment Report as a possible climatic condition. The source area of the Yellow River with complicated permafrost conditions was chosen as the study area. The past and future permafrost distribution were predicted, and the future possible changing trends in permafrost in this area were calculated. The obtained results were, (1) during the past 30 years of 1972-2012, a small part of permafrost was degraded, which covered an area of about 833 km². In this period, the seasonal frozen soil type was mainly distributed in the of Requ river valley, Xiaoyemaling, and Tangchama, as well as the southern part of the two lake basins. (2) Under different climatic scenarios of RCP 2.6, RCP 6.0 and RCP 8.5, little difference would happen on permafrost degradation until 2050. In details, the possible degradation area of permafrost would be 2224 km², 2347 km², and 2559 km² under the scenarios of RCP 2.6, RCP 6.0, and RCP 8.5, respectively, accounting for 7.5%, 7.9%, 8.6% of the total study area. The seasonal frozen soil type would be sporadically distributed in the river valleys of Lena Qu, Duo Qu, Baima Qu, but widely distributed around Yeniugou, Yeniutan and four Madio lakes located in the Yellow River valley in the eastern part of Ngoring Lake. (3) In 2100, the predicted permafrost degradation area would be 5636 km², 9769 km² and 15548 km², respectively, and they would account for 19%, 32.9% and 52.3% of the source area. The permafrost degradation mainly occurred in the areas of Xingsuhai, Gamaletan, Duogerong, of which low-temperature permafrost would be degraded into a high-temperature permafrost type. And the mean annual ground temperature of permafrost would rise differentially. (4) Under the scenario of RCP 2.6, all permafrost with current mean annual ground temperature higher than -0.15oC would be degraded into seasonal frozen soil type, and the permafrost with the mean annual ground temperature ranging from -0.15 oC to -0.44oC would be partly degraded into seasonal frozen soil type. Under the scenarios of RCP 6.0 and RCP 8.5, permafrost with the current mean annual ground temperature higher than -0.21 oC and -0.38 oC would be totally degraded, the permafrost with the mean annual ground temperature ranging from -0.21 to -0.69 oC and from -0.38 oC to -0.88 oC would be partly degraded.