Abstract
Climate warming has intensified permafrost degradation, which could have a variety of implications on the hydrological regime in permafrost regions. In this study, we analyzed the effects of permafrost degradation on the hydrological regime via four hydrological variables for 10 unregulated catchments in the source regions of the Yangtze and Yellow rivers. The results demonstrate that catchments with high permafrost coverage are expected to have an increased winter discharge ratio (proportion of winter discharge contribution to total annual flow), a decreased recession coefficient and a decreased ratio of Qmax/Qmin due to permafrost degradation. However, the great storage effects of lakes and wetlands, which could contribute to more groundwater instead of direct surface discharge, may affect the hydrological effects of permafrost degradation and result in the abnormal performance at catchment scale. The correlation analysis between summer precipitation (July–September) and the following winter discharge (December–February) indicates that permafrost degradation may affect the redistribution of summer precipitation towards the following winter discharge via increasing the soil storage capacity and delaying the release of water into streams in permafrost regions. However, unlike the Arctic and sub-Arctic regions, no significant changes for the hydrological regime (four hydrological variables) are detected over the individual periods of records for each catchment. Decreased precipitation in summer seems to reduce the water infiltration to supply the groundwater, which weakens the effects of permafrost degradation on the hydrological regime. This study implies that the storage effects of lakes and wetlands and the changes of summer precipitation patterns should be considered in future permafrost hydrological simulations, which have suggested that a large increase in groundwater discharge to streams will likely occur in response to permafrost degradation due to the warming climate in the ideal scenario.
Highlights
Global warming due to anthropogenic greenhouse gas emission is amplified in high-latitude [1]and -altitude regions [2], which significantly changes permafrost distribution, and affects hydrological processes and conditions [3,4,5]
Bense et al [16] suggested that a large increase in groundwater discharge to streams for the few centuries will likely occur in response to permafrost degradation due to climate warming
The winter discharge ratio had an increased trend in 5 of the 10 catchments, with only 2 exhibited increased trends that were significant at the p ≤ 0.1 level, and none of these catchments passed the statistical tests at the p ≤ 0.05 level (Table 3)
Summary
Global warming due to anthropogenic greenhouse gas emission is amplified in high-latitude [1]and -altitude regions [2], which significantly changes permafrost distribution, and affects hydrological processes and conditions [3,4,5]. Surface runoff is negligible due to freezing conditions, and river discharge with no direct liquid supply of rainfall but snowfall, is assumed to mainly come from the relatively deep groundwater flowing through the unfrozen parts of the ground [9,10,11,12]. The groundwater is expected to become more and more important due to permafrost degradation, which enhances liquid water infiltration and supports deep flow paths [9,10,11,12]. River [8], and entire pan-Arctic [15] for various time records This increased trend is speculated to have a close relationship to permafrost dynamics. Ge et al [17] demonstrated that a three-fold thickening of the active layer will lead to a three-fold increase in groundwater discharge
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