Intensified warming suppressed the snowmelt in the Tibetan Plateau

Understanding how hydrological factors interrelate is crucial when examining the impact of climate warming on snowmelt.However,these connections are often overlooked,leading to an unclear relationship between temperature and snowmelt.This study investigates the complex interplay between temperature and snowmelt in the Tibetan Plateau from 1961 to 2020,focusing on how extreme high-temperature events affect the frequency of extreme snowmelt.Using a structural equation model,we detected three temperature-related factors that predominantly influenced snowmelt and extreme snowmelt.The annual average temperature was found to have a significant indirect impact on snowmelt,mediated by changes in snowfall,snow depth and snow cover.By contrast,high-temperature days(daily maximum temperatures exceeding the 90th percentile)and heat waves(at least three consecutive high-temperature days)negatively affected extreme snowmelt directly or indirectly.The direct effect of increasing extreme temperature events was associated with an earlier onset of high-temperature periods,which accelerated snowmelt and shortened the duration of extreme snowmelt periods.Additionally,the reduction in snow cover owing to warming emerged as a main factor suppressing snowmelt and extreme snowmelt frequencies.We also revealed spatiotemporal variations in the temperature‒snowmelt relationship that highly depended on changes in snowmelt patterns.The study elucidated why warming suppresses snowmelt and extreme snowmelt events in the Tibetan Plateau,highlighting the mediating roles of snow-related and phenological factors.The findings will provide scientific support for climate simulation and water management policymaking in alpine regions worldwide.

Disaster effects of climate change in High Mountain Asia:State of art and scientific challenges Disaster effects of climate change in High Mountain Asia:State of art and scientific challenges

High Mountain Asia(HMA)shows a remarkable warming tendency and divergent trend of regional precipitation with enhanced meteorological extremes.The rapid thawing of the HMA cryosphere may alter the magnitude and frequency of nature hazards.We reviewed the influence of climate change on various types of nature hazards in HMA region,including their phenomena,mechanisms and impacts.It reveals that:1)the occurrences of extreme rainfall,heavy snowfall,and drifting snow hazards are escalating;accelerated ice and snow melting have advanced the onset and increased the magnitude of snowmelt floods;2)due to elevating trigger factors,such as glacier debuttressing and the rapid shift of thermal and hydrological regime of bedrock/snow/ice interface or subsurface,the mass flow hazards including bedrock landslide,snow avalanche,ice-rock avalanches or glacier detachment,and debris flow will become more severe;3)increased active-layer detachment and retrogressive thaw slumps slope failures,thaw settlement and thermokarst lake will damage many important engineering structures and infrastructure in permafrost region;4)multi-hazards cascading hazard in HMA,such as the glacial lake outburst flood(GLOF)and avalanche-induced mass flow may greatly enlarge the destructive power of the primary hazard by amplifying its volume,mobility,and impact force;and 5)enhanced slope instability and sediment supply in the highland areas could impose remote catastrophic impacts upon lowland regions,and threat hydropower security and future water shortage.In future,ongoing thawing of HMA will profoundly weaken the multiple-phase material of bedrock,ice,water,and soil,and enhance activities of nature hazards.Compounding and cascading hazards of high magnitude will prevail in HMA.As the glacier runoff overpasses the peak water,low flow or droughts in lowland areas downstream of glacierized mountain regions will became more frequent and severe.Addressing escalating hazards in the HMA region requires tackling scientific challenges,including understanding multiscale evolution and formation mechanism of HMA hazard-prone systems,coupling thermo‒hydro‒mechanical processes in multi-phase flows,predicting catastrophes arising from extreme weather and climate events,and comprehending how highland hazards propagate to lowlands due to climate change.