International Journal of Molecular Ecology and Conservation, 2025, Vol.15, No.6, 277-285 http://ecoevopublisher.com/index.php/ijmec 280 change the amount of energy absorbed by the surface, thereby affecting regional temperature, pressure field and atmospheric circulation (Irannezhad et al., 2022). For instance, the reduction of snow cover in the Northern Hemisphere leads to an increase in surface heat absorption, accelerating the warming in high latitudes (Arctic amplification). This mechanism has been jointly verified by satellite observations and model simulations. The melting of snow releases water vapor, which can increase atmospheric humidity and further affect cloud cover and precipitation. In addition, the shortening of snow cover time and the reduction in depth will weaken the "insulation effect" in winter, making the soil more exposed to extreme low temperatures and leading to an increase in deep frozen layers. Snow cover changes constitute an important feedback loop in the climate system by altering surface heat exchange, permafrost structure and vegetation growth rhythm. Once the warming trend caused by the reduction of snow cover expands, it will further reduce the amount of snowfall, forming a typical positive feedback (Richardson et al., 2024). 3.2 Water cycle and water resources supply As one of the world's largest "natural reservoirs", snow cover is the core source of seasonal river replenishment and water supply in mountainous areas. Snow cover water equivalent (SWE) determines the water volume and flow process in spring, and has a decisive impact on the water supply of agricultural and pastoral ecosystems, wetlands and downstream cities. For instance, the melting of snow in the Rocky Mountains regulates over 70% of the water resources in the western United States. The melting rhythm of snow cover is jointly controlled by solar radiation, air temperature, wind speed and the physical structure of snow cover. The early or late release of meltwater directly affects the intensity of flood peaks, wetland water levels and groundwater recharge (Malmros et al., 2018). As the warming trend intensifies, many mountainous areas have witnessed phenomena such as earlier snow melting, accelerated melting speed, and earlier peak spring runoff. This change not only increases the risk of spring flooding, but also aggravates the attenuation of summer runoff, causing an imbalance between water supply and demand (Figure 2) (Wieder et al., 2022). Future scenario simulations generally show that a reduction in snow cover will significantly increase the frequency of seasonal hydrological extreme events. Figure 2 Increase in the winter snowmelt fraction and earlier center timing of runoff also show increased variability (Adopted from Wieder et al., 2022) Image caption: Panels show changes in the fraction of winter snowmelt that occurs before peak SWE and date of center timing of runoff (Left and Right columns, respectively), including (A and B) change in the ensemble mean state, (C and D) percent change in the ensemble SD (after removing the ensemble mean), and (E and F) the time of emergence with associated changes in global mean temperature. Changes in ensemble mean and SD were calculated as the difference across all ensemble members at the end of the 21st century (2070 through 2099) from a 30-y baseline period in the mid-20th century (1940 to 1969). As in, the time of emergence was calculated as the year when the 10-y running mean was ± 2 SD outside of the ensemble mean from 1940 to 1969. The color bar range in (C and D) was chosen to facilitate comparison of changes in variability between metrics. Gridcells in the domain that are not colored in (E and F) do not emerge by 2100 (Adopted from Wieder et al., 2022)
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