Bacterial community diversity of meltwater runoff and soil in Midre Lovénbreen glacier in Ny-Alesund,Arctic

Glacial meltwater runoff is a dynamic ecosystem.On the one hand,nutrient concentration changes as it flows from upstream to downstream,and on the other hand,bacterial community structure changes due to its contact with nearby soil during the flow process.We studied meltwater and soil in the Midre Lovénbreen glacier region,to explore changes in bacterial diversity as meltwater flows,and the relationship between meltwater and soil bacterial diversity.As glacial meltwater flows from upstream to downstream,the relative abundance of dominant bacterial groups changes.In addition,we found that during the flowing process,nutrient exchange and bacterial contact had occurred between the meltwater runoff and the soil.As a result,the distribution patterns of some bacteria in the meltwater are very similar to those in the soil.Finally,we combined distance-based redundancy analysis and weighted correlation network analysis to show that NO_(3)^(-)-N and NO_(2)^(-)-N are the most two significant factors affecting glacial meltwater and soil,respectively.Our results suggest that in such a close-knit ecosystem,the interaction of glacial meltwater with soil,as well as environmental factors,together determine bacterial community composition.

Glacier mass balance and its impacts on streamflow in a typical inland river basin in the Tianshan Mountains, northwestern China

Glaciers are known as natural ’’solid reservoirs’ ’, and they play a dual role between the composition of water resources and the river runoff regulation in arid and semi-arid areas of China. In this study, we used in situ observation data from Urumqi Glacier No. 1, Xinjiang Uygur Autonomous Region, in combination with meteorological data from stations and a digital elevation model, to develop a distributed degree-day model for glaciers in the Urumqi River Basin to simulate glacier mass balance processes and quantify their effect on streamflow during 1980–2020. The results indicate that the mass loss and the equilibrium line altitude(ELA) of glaciers in the last 41 years had an increasing trend, with the average mass balance and ELA being-0.85(±0.32) m w.e./a(meter water-equivalent per year) and 4188 m a.s.l., respectively. The glacier mass loss has increased significantly during 1999–2020, mostly due to the increase in temperature and the extension of ablation season. During 1980–2011, the average annual glacier meltwater runoff in the Urumqi River Basin was 0.48×108 m3, accounting for 18.56% of the total streamflow. We found that the annual streamflow in different catchments in the Urumqi River Basin had a strong response to the changes in glacier mass balance, especially from July to August, and the glacier meltwater runoff increased significantly. In summary, it is quite possible that the results of this research can provide a reference for the study of glacier water resources in glacier-recharged basins in arid and semi-arid areas.

Lake water storage change estimation and its linkage with terrestrial water storage change in the northeastern Tibetan Plateau

Tibetan Plateau(TP) lakes are important water resources,which are experiencing quick expansion in recent decades.Previous researches mainly focus on analyzing the relationship between terrestrial water storage(TWS) change and lake water storage(LWS) change in the total inner TP,it is still lack of researches about the spatial difference and the characteristic of sub-region in the inner TP.In this study,we estimated the area change of 34 lakes by using Landsat images in the northeastern TP during 1976–2013,and LWS change by using the Shuttle Radar Topography Mission(SRTM).The results suggested that LWS had shrunk from 1976 to 1994,and then expanded quickly until 2013.LWS had a serious decrease by 13.6 Gt during 1976–1994,and then it increased quickly by 35.4 Gt during 1994–2013.We estimated TWS change,soil moisture change,and permafrost degradation based on the satellite data and related models during 2003–2013.The results indicated that their changing rates were 1.86 Gt/y,0.22 Gt/y,and –0.19 Gt/y,respectively.We also calculated the change of groundwater based on the mass balance with a decreasing trend of –0.054 Gt/y.The results suggested that the cause of TWS change was the increase of LWS.We analyzed the cause of lake change according to water balance,and found that the primary cause of lake expansion was the increasing precipitation(80.7%),followed by glacier meltwater(10.3%) and permafrost degradation(9%).The spatial difference between LWS change and TWS change should be studied further,which is important to understand the driving mechanism of water resources change.

Runoff components and the contributions of precipitation and temperature in a highly glacierized river basin in Central As

Understanding the main drivers of runoff components and contributions of precipitation and temperature have important implications for water-limited inland basins,where snow and glacier melt provide essential inputs to surface runoff.To quantify the impact of temperature and precipitation changes on river runoff in the Tarim River basin(TRB),the Hydrologiska Byrans Vattenbalansavdelning(HBV)-light model,which contains a glacier routine process,was applied to analyze the change in runoff composition.Runoff in the headstream parts of the TRB was more sensitive to temperature than to precipitation.In the TRB,overall,rainfall generated 41.22%of the total runoff,while snow and glacier meltwater generated 20.72%and 38.06%,respectively.These values indicate that temperature exerted more major effects on runoff than did precipitation.Runoff compositions were different in the various subbasins and may have been caused by different glacier coverages.The runoff volumes generated by rainfall,snowmelt,glacier melt was almost equal in the Aksu River subbasin.In the Yarkand and Hotan River subbasins,glacier meltwater was the main supplier of runoff,accounting for 46.72%and 58.73%,respectively.In the Kaidu-Kongque River subbasin,80.86%was fed by rainfall and 19.14%was fed by snowmelt.In the TRB,runoff generated by rainfall was the dominant component in spring,autumn,winter,while glacier melt runoff was the dominant component in summer.Runoff in the TRB significantly increased during 1961–2016;additionally,56.49%of the increase in runoff was contributed by temperature changes,and 43.51%was contributed by precipitation changes.In spring,the runoff increase in the TRB was mainly caused by the precipitation increase,opposite result in summer and autumn.Contribution of temperature was negative in winter.Our findings have important implications for water resource management in high mountainous regions and for similar river basins in which melting glaciers strongly impact the hydrological cycle.

conomic losses from reduced freshwater under future climate scenarios: An example from the Urumqi River,Tianshan Mountains

As important freshwater resources in alpine basins,glaciers and snow cover tend to decline due to climate warming,thus affecting the amount of water available downstream and even regional economic development.However,impact assessments of the economic losses caused by reductions in freshwater supply are quite limited.This study aims to project changes in glacier meltwater and snowmelt of the Urumqi River in the Tianshan Mountains under future climate change scenarios(RCP2.6(RCP,Representative Concentration Pathway),RCP4.5,and RCP8.5)by applying a hydrological model and estimate the economic losses from future meltwater reduction for industrial,agricultural,service,and domestic water uses combined with the present value method for the 2030 s,2050 s,2070 s,and 2090 s.The results indicate that total annual glacier meltwater and snowmelt will decrease by 65.6%and 74.5%under the RCP4.5 and RCP8.5 scenarios by the 2090 s relative to the baseline period(1980-2010),respectively.Compared to the RCP2.6 scenario,the projected economic loss values of total water use from reduced glacier meltwater and snowmelt under the RCP8.5 scenario will increase by 435.10×10^(6) and 537.20×10^(6) CNY in the 2050 s and 2090 s,respectively,and the cumulative economic loss value for 2099 is approximately 2124.00×10^(6) CNY.We also find that the industrial and agricultural sectors would likely face the largest and smallest economic losses,respectively.The economic loss value of snowmelt in different sectorial sectors is greater than that of glacier meltwater.These findings highlight the need for climate mitigation actions,industrial transformation,and rational water allocation to be considered in decision-making in the Tianshan Mountains in the future.

Response of runoff and its components to climate change in the Manas River of the Tian Shan Mountains

A warming-wetting climate trend has led to increased runoff in most watersheds in the Tian Shan Mountains over the past few decades.However,it remains unclear how runoff components,that is,rainfall runoff(Rrain),snowmelt runoff(Rsnow),and glacier meltwater(Rglacier),responded to historical climate change and how they will evolve under future climate change scenarios.Here,we used a modified Hydrologiska Byrans Vattenbalansavdelning(HBV)model and a detrending method to quantify the impact of precipitation and temperature changes on runoff components in the largest river(Manas River)on the northern slope of the Tian Shan Mountains from 1982 to 2015.A multivariate calibration strategy,including snow cover,glacier area,and runoff was implemented to constrain model parameters associated with runoff components.The downscaled outputs of 12 general circulation models(GCMs)from the Sixth Coupled Model Intercomparison Project(CMIP6)were also used to force the modified HBV model to project the response of runoff and its components to future(2016-2100)climate change under three common socio-economic pathways(SSP126,SSP245,and SSP585).The results indicate that Rrain dominates mean annual runoff with a proportion of 42%,followed by Rsnow(37%)and Rglacier(21%).In terms of inter-annual variation,Rrain and Rsnow show increasing trends(0.93(p<0.05)and 0.31(p>0.05)mm per year),while Rglacier exhibits an insignificant(p>0.05)decreasing trend(-0.12 mm per year),leading to an increasing trend in total runoff(1.12 mm per year,p>0.05).The attribution analysis indicates that changes in precipitation and temperature contribute 8.16 and 10.37 mm,respectively,to the increase in runoff at the mean annual scale.Climate wetting(increased precipitation)increases Rrain(5.03 mm)and Rsnow(3.19 mm)but has a limited effect on Rglacier(-0.06 mm),while warming increases Rrain(10.69 mm)and Rglacier(5.79 mm)but decreases Rsnow(-6.12 mm).The negative effect of glacier shrinkage on Rglacier has outweighed the positive effect of warming on Rglaciers resulting in the tipping point(peak water)for Rglacier having passed.Runoff projections indicate that future decreases in Rglacier and Rsnow could be offset by increases in Rrain due to increased precipitation projections,reducing the risk of shortages of available water resources.However,management authorities still need to develop adequate adaptation strategies to cope with the continuing decline in Rgacier in the future,considering the large inter-annual fluctuations and high uncertainty in precipitation projection.