概述永久冻土是指在自然气象条件下冻结状态持续三年以上的土层,也称多年冻土。在温度的影响下,永久冻土可能发展和退化。若土层每年吸热比散热多,地温逐年升高,使永久冻土层逐渐融化变薄以致消失,即为退化永久冻土;反之为发展永久冻土。然而随地球表面温度的升高,退化永久冻土占多数。在永久 Overview Permafrost is a layer of soil that has been frozen for more than three years under natural weather conditions, also known as permafrost. Under the influence of temperature, permafrost may develop and degrade. If the soil absorbs more heat per year than the heat, the ground temperature rises year by year, so that the permafrost layer gradually melts and thins and disappears, that is, the degraded permafrost; otherwise it is the development of permafrost. However, as the surface temperature of the earth increases, the number of degraded permafrost accounts for the majority. Permanent