Geotextile protection of glacier:Observed and simulated impacts on energy and mass balance

The detailed physical processes involved in slowing glacier ablation by material cover remain poorly understood so far.In the present study,using the snow cover model SNOWPACK,the effect of geotextile cover on the energy and mass balance at the tongue of the Urumqi Glacier No.1(Chinese Tien Shan)was simulated between July 12,2022 and August 31,2022.The mass changes and the energy fluxes with and without material cover were compared.The results indicated that the geotextile covering reduced glacier ablation by approximately 68%compared to the ablation in the uncovered regions.The high solar reflectivity of the geotextile reduced the net short-wave radiation energy available for the melt by 45%.Thermal insulation of the geotextile reduced the sensible heat flux by 15%.In addition,the wet geotextile exerted a cooling effect through long-wave radiation and negative latent heat flux.This cooling effect reduced the energy available for ablation by 20%.Consequently,only 37%of the energy was used for melting compared to that used in the uncovered regions(67%).Sensitivity experiments revealed that the geotextile cover used at a thickness range of 0.045-0.090 m reduced the ice loss by approximately 68%-72%,and a further increase in the thickness of the geotextile cover led to little improvements.A higher temperature and greater wind speed increased glacier ablation,although their effects were small.When the precipitation was set to zero,it led to a significantly increased melt.Overall,the geotextile effectively protected the glacier tongue from rapid melting,and the observed results have provided inspiration for developing an effective and sustainable approach to protect the glaciers using geotextile cover.

Do abrupt cryosphere events in High Mountain Asia indicate earlier tipping point than expected?

Tipping points of about 16 elements have been identified in Earth system,yet cryospheric tipping point of specific Alpine region has not been studied.Here we analyzed three tipping elements(mountain glacier,snow cover,and permafrost)identified in recent years,evidenced by the facts of frequent occurrence of abrupt massive collapse of glacier mass and the widespread thermakarst of permafrost.Since 2015,strikingly abrupt cryosphere events(ACEs)have been consistently observed over a large range of High Mountain Asia(HMA).Those events were un-precedentedly significant in history,leading to collapses of glaciers following by disconnection of glacier tongue from accumulation basin and recession of thermakarst towards higher elevation.Strong decreasing of snow depth in 2022 was also observed since 2021/2022 winter,coinciding with extreme warming of the year.The widespread high warming rates in the last two decades over HMA might have triggered above ACEs.The dynamic thresholds of ACEs depend largely on high temperature,especially extreme heat wave,for both glaciers and permafrost,closely related to meltwater as a key factor for reaching initial conditions of abrupt changes,suggesting HMA cryosphere is a tipping element under the global warming level of 1.1℃.The ACEs can cause tremendous damage to local ecosystem and socioeconomy,measures to mitigate risks should be taken when the tipping points are reached.

Rapid mass loss and disappearance of summer-accumulation type hanging glacier

Hanging glaciers hold the absolute dominant number in West China and their changes had important influences on local hydrology,sea-level rise and natural hazards(snow/ice avalanches).However,logistic and operational difficulties have resulted in the lack of in-situ-measured data,leaving us with poor knowledge of the changing behaviors of this type of glacier.Here,we presented the spatiotemporal pattern of seasonal and annual mass changes of a mid-latitude hanging glacier in the Tien Shan based on repeated terrestrial laser scanning(TLS)surveys during the period 2016-2018.The distributed glacier surface elevation changes exhibited highly spatiotemporal variability,and the winter elevation changes showed slight surface lowering at the upper elevations and weak thickening at the glacier terminus,which was contrary to altitudinal elevation changing patterns at the summer and annual scales.Mass balance processes of the hanging glacier mainly occurred during summer and the winter mass balance was nearly balanced(-0.10±0.15 m w.e.).The glacier exhibited more rapid mass loss than adjacent other morphological glacier and the estimated response time of the glacier to climate change was very short(6-9 years),indicating hanging glaciers will experience rapid wastage and disappearance in the future even with climate change mitigation.