多年冻土过渡带研究进展与展望  

Research Progress and Prospect of Transition Zone in Permafrost

作　　者：罗栋梁 刘佳 陈方方 李世珍 Luo Dongliang;Liu Jia;Chen Fangfang;Li Shizhen(Key Laboratory of Cryospheric Science and Frozen Soil Engineering,Northwest Institute of Eco-Environment and Resources,CAS,Lanzhou 730000,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院西北生态环境资源研究院冰冻圈科学与冻土工程重点实验室,甘肃兰州730000 [2]中国科学院大学,北京100049

出　　处：《地球科学》2024年第11期4063-4081,共19页Earth Science

基　　金：甘肃省科技重大专项(No.23ZDFA017);陇原青年英才项目(No.E4390601);国家自然科学基金项目(No.U2243214);中国科学院西部青年学者项目(No.E2290601).

摘　　要：随着气候临界点的迫近,多年冻土两层分层体系的局限性日益凸显,因此有必要单独考虑多年冻土上部即过渡带的特殊性质.通过系统梳理已有研究发现:(1)过渡带是多年冻土区内成冰和过剩冰的主要分布带,广泛分布于粉黏土中及部分细粒多孔且冻结敏感性强的风化基岩地带,地下冰多为分凝冰、脉冰和大块冰,冷生构造主要为透镜状、层状、网状和斑杂状等,其变化与热融沉陷和斜坡地带热融滑塌、融冻泥流和活动层滑脱等现象密切相关;(2)其蕴含的丰富有机质和腐殖质常与多年冻土的加积和重复分凝成冰过程伴生,是重建冻土形成时气候与环境的可靠替代性指标;(3)多年冻土退化的程度和幅度与过渡带的厚度、冷生构造、地下冰和有机质含量等内在性质密不可分,呈现极强的时空异质性,其因地下冰巨大相变潜热效应而减缓甚至阻抗多年冻土退化,但一旦融化即产生临界点效应,由此多年冻土退化加速,热喀斯特现象激增,并造成上覆工程构筑物失稳.因此,亟待开展包含过渡带的气候环境重建、生态水文效应、力学性能和结构性质的演化与冻土精准模拟研究.As one of the critical climatic elements of the Earth system,the permafrost is approaching its climatic tipping point,highlighting the limitations of its two-layered structure consisting of active layer and perennially frozen layer.Therefore,it is necessary to consider the transition zone situated between the active layer and perennially frozen layer,which has specific properties,as a separate layer.The transition zone is the ice-rich upper part of permafrost,which thaws over sub-decadal to centennial time scales,particularly during extremely warm and wet summers,becoming part of the active layer.It comprises an ice-rich transient layer and an icier intermediate layer.The cryostructures,thermophysical properties,and mechanical structures of the transition zone are distinct from both overlying active layer and underlying permafrost,below which is the“authentic”permafrost.Under the combined influence of global climate warming and anthropogenic activities,the degree and extent of permafrost degradation are related to external forcing factors such as climate,environment,basic properties of watershed,and human activities,as well as internal properties like the thickness and position of the transition zone,cryogenic structures,ground ice,and organic matter content,displaying strong spatiotemporal heterogeneity.Research shows that transition zone is widely distributed in silty-clay and parts of frost-susceptible weathered bedrocks with fine-grained pores.It is the main distribution zone of intrasedimental ice and excess ice,with ground ice mainly existing as segregated ice,vein ice,and massive ice.The cryostructures are primarily lenticular,layered,reticular,and ataxitic,and their changes are closely related to phenomena such as thermal subsidence,thermokarst slumping,solifluctions,and active layer detachment.The rich organic matter and humus contained within are often associated with permafrost aggradation and repeated segregation ice formation processes,serving as reliable proxies for reconstructing the climate an

关 键 词：多年冻土地下冰 过渡带 转换层 中间层 气候临界点 生态学 环境地质. 

分 类 号：P66[天文地球—地质学]