Abstract:

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.

Key words: the source area of the Yellow River, permafrost changes, spatial distribution, change characteristics, numerical simulation