1961-2020年三江源地区季节性冻土冻融特征分析

基于1961-2020年三江源地区21个气象观测站点逐日冻土深度、平均气温和降水资料,利用数理统计方法分析了季节性冻土冻结初始日、融化终止日、最大冻结深度的时空分布特征及其与气温、降水的关系。结果表明：1961-2020年,三江源地区季节性冻土平均冻结初始日始于9月下旬至10月下旬,融化终止日多出现在4-5月。近60年来,三江源地区季节性冻土冻结初始日（融化终止日）显著推迟（提前）,尤其是20世纪90年代以来,推迟（提前）尤为明显。三江源地区季节性冻土年最大冻结深度呈显著减小趋势,进入21世纪后,尤其是近10年来最大冻结深度减小明显。在空间分布上,冻结初始日、融化终止日、年最大冻结深度的分布主要受海拔的影响,冻结初始日（融化终止日）由高海拔向低海拔逐渐推迟（提前）,年最大冻结深度也由高海拔向低海拔逐渐变浅。近60年来,三江源气候暖湿化导致季节性冻土封冻时间缩短、年最大冻结深度变浅。冻结初始日与10月气温、降水的正相关最高,融化终止日与气温和降水的负相关性在4月达最大,年最大冻结深度与1月气温和上一年8月降水呈显著负相关性。

Freeze-Thaw Characteristics of Seasonally Frozen Ground in the Three River Source Region from 1961 to 2020

Based on the data of daily maximum freezing depth of the seasonally frozen ground, near surface air temperature and precipitation from 21 meteorological stations in the three river source region during 1961 to 2020, by using mathematical statistics method, the spatial-temporal characteristics of freezing start date, thawing end date and annual maximum freezing depth of seasonally frozen ground and their relationship with air temperature and precipitation were analyzed. The results demonstrated that the freezing start date of seasonally frozen ground in the Three River Source region mostly occurred from late September to late October, and the thawing end date mostly occurred from April to May. During recent 60 years, the freezing start date of seasonally frozen ground in the Three River Source region was significantly delayed, and the thawing end date was significantly advanced, especially since 1990s. In the 21st century, especially in the past 10 years, the annual maximum freezing depth has decreased remarkably. The spatial distribution of freezing start date, thawing end date and annual maximum freezing depth of seasonally frozen soil in the Three River Source region was mainly linked to elevation. The freezing start date(the thawing end date)was gradually delayed(advanced)from high to low altitude, and the maximum freezing depth gradually decreased from high to low altitude. In recent 60 years, the warmer and wetter climate in the Three River Source region was linked to the delayed of the freezing start date, the advance of the thawing end date and the decrease of the annual maximum freezing depth. The average freezing start date and thawing end date were highly correlated with the temperature and precipitation in October and April, respectively, and the annual maximum freezing depth had the highest correlation with the temperature in January and the precipitation in August of the previous year. © 2022 Authors. All rights reserved.