| Summary: | Permafrost is an important component in hydrological processes because changes in runoff over the Arctic drainage basin cannot be well explained by changes in precipitation-related variables. However, current understanding of the influences of permafrost on hydrological dynamics is insufficient. This study investigated historical variations in permafrost conditions and their potential hydrologic effects over the Russian Arctic drainage basin. The results show that soil temperature (at 0.40 m below surface) has increased about 1.4 °C over the Ob, 1.5 °C over the Yenisei, and 1.8 °C over the Lena River basin from 1936 through 2013, possibly resulted in a significant thawing of permafrost. Rapid active layer changes have occurred since the 1970s. The volume of the active layer increased by 28, 142, and 228 km3 over the Ob, Yenisei, and Lena basins, respectively, since the 1970s. Melting ground ice caused by deepening active layer may be a limited contribution to annual runoff. Runoff during freeze season (October–April) showed significant positive correlations (p < 0.05) to active layer thickness in the Yenisei and Lena basins while negative correlation (p > 0.05) in the Ob basin. These results imply that, in basins with high permafrost coverage, a deeper active layer increased soil water storage capacity and perhaps contribute to an increase in winter runoff.
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