Permafrost Carbon Release Risk Assessment In Qinghai Province Based On Multiple Permafrost Product Data Sets

The Qinghai-Tibet Plateau is the largest area of permafrost outside the circum-Arctic region,known as the " third pole " of the earth.Qinghai Province is located in the hinterland of the Qinghai-Tibet Plateau,and the soil organic carbon stored in its permafrost region may become a potential carbon source in the context of climate change.However,the storage and distribution of these permafrost carbons are still unclear,and the risk of thawing needs to be evaluated.In this study,the published frozen soil data set was verified by the accuracy and linear fitting of the measured data.The most suitable permafrost area product data and thickness product data for Qinghai Province were selected.The soil sample data were measured by field collection and laboratory experiments.Based on the soil type method,the organic carbon density and organic carbon storage of the lower limit of 0-30 cm,30-60 cm,60-120 cm,120-150 cm,and 150 cm-active layer of different soil types were calculated by using the thickness,bulk density,and organic matter of the soil layer.At the same time,based on the changes in permafrost area and thickness of RCP2.6,RCP4.5 and RCP8.5 under different paths of CMIP5(2060-2080),the risk of carbon release in the next 2060-2080 was estimated.The main conclusions are as follows :(1)The selection results of frozen soil data set products.Among the six frozen soil product area data products,the newly drawn frozen soil distribution map(2017)of the Qinghai-Tibet Plateau released by Zhao Lin et al.was verified by the permafrost observation data set,and the accuracy reached 95.68 %.Among the three permafrost active layer thickness data products,Ran Youhua et al.’ s ’ The current state and past change data set of the third polar permafrost ’ was linearly fitted with the field measured observation points,and the R2 reached 93 %.This study selected these two data to calculate the SOC area(1.060 million km2)and thickness(0-6.6m)parameters of permafrost.(2)The organic carbon density of permafrost in Qinghai Province was calculated based on field sampling and soil type method.The results showed that the SOC of 0-30 cm soil in permafrost layer was about 2.28 Pg.SOC in 30-60 cm soil was2.27Pg;s OC in 60-120 cm soil was 2.36Pg;s OC in 120-150 cm soil was 3.25Pg;the SOC of 0-150 cm in Qinghai Province is 10.01 Pg,the SOC of 150 cm-active layer is3.1 Pg,and the SOC of permafrost active layer in Qinghai Province is 13.11 Pg.(3)The low-end,middle-end and high-end paths representing the range of future forced paths in the CMIP5 climate scenario are selected : RCP2.6,RCP4.5 and RCP8.5 paths simulate the permafrost active layer and ground temperature(ground temperature < 0 °C as permafrost range)products,and the permafrost area under2021-2080 RCP2.6,RCP4.5 and RCP8.5 paths is calculated to decrease by 16.49 %,28.65 % and 61.37 %,respectively.The thickness of permafrost active layer increased by 0.22 m,0.24 m and 0.47 m respectively,and the permafrost carbon release may reach 1.79 Pg,2.90 Pg and 6.64 Pg.