2003—2020年青藏高原冻融侵蚀时空变化特征

The spatiotemporal variations in freeze-thaw erosion in 2003—2020 on the Qinghai-Tibet Plateau

全球气候变暖导致青藏高原永久冻土逐渐退化,并增加了季节性冻土的面积,但对冻融侵蚀时空变化还缺乏系统的认识。通过权重法对年冻融日循环天数、日冻融相变水量、植被覆盖度、年均降雨量、坡度和坡向6个冻融侵蚀因子进行赋权,分析青藏高原2003—2020年不同强度的冻融侵蚀时空变化和主导驱动因素。结果表明:(1)2003—2020年青藏高原平均冻融侵蚀面积为(161.37±0.42)×10^(4)km^(2),占青藏高原面积的64.55%,中度及以上侵蚀占冻融侵蚀面积的63.0%,强烈、极强烈和剧烈侵蚀主要分布在雅鲁藏布江流域、昆仑山-祁连山、帕米尔高原地区;(2)2003—2020年青藏高原冻融侵蚀表现为加剧趋势,加剧的区域达到29.79×10^(4)km^(2),占青藏高原面积的11.6%;2003—2010年中度及以上平均侵蚀面积为(95.71±3.33)×10^(4)km^(2),2013—2020年为(107.60±3.20)×10^(4)km^(2),其面积增加了11.89×10^(4)km^(2),增强的区域主要分布在可可西里山、冈底斯山、藏北高原及三江源地区。(3)日均冻融相变水量变化对侵蚀强度变化的平均贡献率最大,为49.59%,贡献高值区主要位于藏北高原的多年冻土区;年冻融日循环时间变化对侵蚀强度的平均贡献次之,为40.55%。在冻融侵蚀减弱的区域,植被盖度的平均贡献达37.69%。植被覆盖上升减轻了冻融侵蚀,气候变暖加速了冻融侵蚀,但是植被对冻融侵蚀的减轻作用不足以抵消气候变暖背景下相变水量对冻融侵蚀的增强作用。另外,在侵蚀等级增强的区域,最低温的增幅大于最高温的增幅。研究提升了气候、植被变化背景下对青藏高原冻融侵蚀强度时空变化及其驱动机制的认识,为青藏高原冻融侵蚀治理提供了理论依据。

On the Qinghai-Tibet Plateau,global warming has led to the gradual melting of permafrost and increased the area of seasonal permafrost.However,there is still a lack of systematic understanding of the spatiotemporal changes in freeze-thaw erosion.Using the weight method,where 6 evaluating factors(annual freeze-thaw cycle days,average daily phase change water,vegetation cover,average annual precipitation,slope,and aspect)were selected,our study determined the spatiotemporal variations in freeze-thaw erosion and their driving factors during 2003—2020 on the Qinghai-Tibet Plateau.The results showed that:(1)From 2003 to 2020,the average freeze-thaw erosion area of the Qinghai Tibet Plateau was(161.37±0.42)×10^(4) km^(2),accounting for 64.55%of the total area of the Qinghai Tibet Plateau.Moderate and above erosion accounted for 63.0%of the area of freeze-thaw erosion.Intense,extremely intense,and severe erosion was mainly distributed in the Yarlung-Zangbo River basin,Kunlun-Qilian Mountains,and Pamirs Plateau;(2)From 2003 to 2020,the freeze-thaw erosion of the Qinghai Tibet Plateau has been strengthened,with a strengthened area of 29.79×10^(4) km^(2),accounting for 11.6%of the total area of the Qinghai Tibet Plateau.The area of moderate and above erosion was(95.71±3.33)×10^(4) km^(2)in 2003—2010 and(107.60±3.20)×10^(4) km^(2)in 2013—2020,with an increasing area of 11.89×10^(4) km^(2).The strengthened area was mainly distributed in Hoh Xil Mountain,Gangdis Mountain,Northern Tibetan Plateau,and Sanjiangyuan region.(3)The average contribution rate of everage daily phase freeze-thaw change water variation to the change in erosion intensity was the largest,with a value of 49.59%,and the high contribution area was mainly located in the permafrost region of the northern Tibetan plateau.The annual freeze-thaw cycle daysvariation played a less important role than the daily mean freeze-thaw phase change water variation in affecting erosion intensity,with a contribution rate of 40.55%.In the area where freeze-thaw erosion was weakened,the average contribution rate of vegetation coverage was 37.69%.The increase in vegetation cover alleviated freeze-thaw erosion,while climate warming accelerated the freeze-thaw erosion.However,the negative effect of vegetation on freeze-thaw erosion cannot offset the positive effect of everage daily phase freeze-thaw change water in the context of climate warming.In addition,in the area where the erosion level was strengthened,the increasing rate of the lowest temperature was greater than that of the highest temperature.This study improved the understanding of the spatial and temporal variations in freeze-thaw erosion intensity and their driving mechanisms on the Qinghai Tibet Plateau in the context of climate and vegetation changes,which may provide a theoretical basis for the control of freeze-thaw erosion on the Qinghai Tibet Plateau.