Fast ice thickness in the Laptev sea according to the polar stations data

The series of data on the fast ice thickness and the surface air temperature of the Roshydromet ground-based polar stations in the Laptev Sea are analyzed. During the analysis the characteristics values for the last 15-year period (2005-2020) are compared to the observations till 2004, and the changes corresponding to the new climatic conditions are revealed. Over the past 15 years the average ice thicknesses at the time of maximum build-up (maximum ice thickness) have decreased by 6% on average at sea. The ice build-up process has become much slower, the overstep from one stage of ice development to another is observed 1-2 ten-days periods later. The air temperature at the considered stations was on average 3°C higher than in the previous period. The most significant changes are observed in the autumn months (October, November) and in April. Averaged over the Laptev Sea stations the sum of the frost degree-days decreased by 15%; all 15 recent winter seasons can be classified as mild. It was revealed that the decrease of the frost degreedays is in a good agreement with the decrease of the mean-seasonal ice thickness (averaged for November-May) at the stations. This indicator seems to be more informative than the maximum ice thickness for changes estimation. Averaging over all stations revealed a 10% decrease of the meanseasonal ice thickness over the past 15 years.