Abstract: Based on frozen soil observation data,daily average ground temperature,daily average air temperature,and extreme minimum air temperature from six meteorological stations in Dalian city from October 1970 to April 2021,this study analyze the spatiotemporal variation characteristics of maximum frozen soil depth in Dalian over the past 51 years and explore its response to climate warming using wavelet analysis,linear regression analysis,and the Mann-Kendall (M-K) test.The results show that the maximum frozen soil depth was at a climate tendency rate of -6.9 cm/10 a,the average annual duration of frozen soil is 117 days,with a decreasing trend at the climate tendency climate tendency rate of -7.2 days/10 a.The onset of freezing is increasingly delayed,while the end date advances,with the average onset and end dates being November 20 and March 18,respectively.The maximum frozen soil depth exhibited periodic variation characteristics at 4 scales,with the 16-26 year period being the most significant.Correlation analysis reveals that ground temperature,air temperature,and extreme minimum temperature are all significantly negatively correlated with maximum frozen soil depth,with ground temperature exerting the strongest influence.

Key words: Freeze-thaw duration, Maximum frozen soil depth, M-K test, Wavelet analysis