Recent climate and hydrological changes in the Tianshan Mountains, Central Asia
0
Citation
0
Reference
10
Related Paper
Abstract:
Global warming accelerates the water cycle worldwide, and directly affects hydrological changes and may cause changes in water availability. The Tianshan Mountains, known as “water tower of Central Asia”, is situated in the Eurasia hinterland. It serves as the main water source and ecological barrier in Central Asia. Most rives originated from the Tianshan Mountains are recharged with rainfall, glacier melt and snow meltwater. The hydrological processes in the Tianshan Mountains are strongly affected by changes in temperature and precipitation, as well as changes in the snow and glaciers. Increases in temperature have important consequences for the hydrological cycle, particularly in areas dominated by glacier and snow melt.This study systematically investigated precipitation and temperature changes and their impacts on glaciers, snow cover and hydrological processes in the Tianshan Mountains using station observations, remote sensing data and reanalysis data. In a warming climate, precipitation is more likely to occur as rainfall rather than snowfall. Temperature-induced precipitation shifted from snow to rain since mid-1990s, with S/P experiencing an overall declining trend at a rate of 0.5%/decade. In addition, an overall increase in extreme precipitation was detected, as reflected in 25 indices. The number of consecutive dry days decreased from 87.02 to 69.35 while the number of consecutive wet days increased from 3.89 to 4.61. Changes in extreme precipitation frequency were shown to increase with event rareness. For R95p, the observed changes in frequency are 34.46%, but these jump to 96.58% for R99p.  By creating a long-term, high-quality, daily snow cover extent (HMASCE) product (1982–2019, spatial resolution of 5 km), the spatial and temporal variability in snow metrics (snow cover area and snow cover phenology) has investigated. Snow cover in the Tian Shan region showed a slight increase during this period, mainly in West Tianshan (0.66% a-1), Hissar Alay (0.64% a-1), and East Tianshan (0.24% a-1).Approximately 97.52% of glaciers in the Tianshan Mountains showed a retreating trend. For the northern TianShan Mountains,  total area and volume of glaciers exhibited negative trends, decreased by 456.43 km2 (16.08%) and 26.14 km3 (16.38%), respectively, from 1990 to 2015. The reduction in the glacier area exhibited an accelerating trend, with a decreasing rate of 0.60% a-1 before 2000, but of 0.71% a-1 after 2000. River runoff responds in a complex way to changes in climate and cryosphere. For example, the runoffs of the Kaidu River and the Aksu River, located in the south flank of the Tianshan Mountains, have increased by 27.4% and 14.4%, respectively, during 1960 to 2021. The total water storage in the Tianshan Mountains also experienced a significant decreasing trend with a rate of 12.12 mm a-1 during 2020~2021..This study sheds light on current and future changes in water cycle under global warming in the Tianshan Mountains. More efforts should be made on the interpretation of impacts and mechanisms of these changes on runoff, which is a key factor that controls the amount and seasonality of freshwater resources for domestic and agricultural needs.Keywords:
Meltwater
Water cycle
Central Asia
In order to demonstrate the spatial and temporal variations in meltwater chemistry at both the lysimeter (0.25 m 2 ) and basin scale, field measurements of snowmelt were conducted in northern Canada. These observations show that microscale variations in flow volume are accompanied by variations in meltwater chemistry. For example, the solute concentrations were largest in areas with low flow, while the largest mass flux occurred in the areas with highest flow. The observed variations in both concentration and mass flux can be quantitatively described by the relationships described by Hibberd [1984). The field measurements clearly demonstrate that in order to estimate the average meltwater chemistry, it is necessary to sample the flow field at a scale similar to that required to average the lateral variations in meltwater volume. Variations in meltwater runoff chemistry also occur at the basin scale due to changes in snowcover depth and the resulting differences in the timing of meltwater release. For example, at this site, meltwater release occurs up to a week earlier from the shallow snow covers than for the deeper snow covers. It would be expected that this asynchronous meltwater runoff would result in a smoothing of the ionic pulse at the basin scale, with lower peak values and a more gradual decline in concentration when compared with meltwater at a point.
Meltwater
Snowmelt
Lysimeter
Cite
Citations (59)
Rock glacier
Cite
Citations (144)
The Isotope based Hydrograph Separation (IHS) has been instrumental in understanding the partitioning of streamflow sources and processes. However, uncertainties persist in the accuracy of IHS estimations and the appropriate definition and sampling of endmembers. To address these uncertainties, we used field data of snowpack, snowfall, and snow meltwater isotopes (δ18O) from Pallas, Northern Finland to estimate the total meltwater contribution during the snowmelt period. We investigated the biases resulting from the application of different sampling strategies for event water endmember. The total meltwater contribution to streamflow was 59.6 % (±2% uncertainty) using the time-variant rolling runoff-corrected melt flux-weighted meltwater 18O isotope value. However, replacing it with either snowfall or winter snowpack 18O isotope weighted average values underestimated the meltwater contribution by 17.8 % or 22.6 %, respectively. Conversely, using time-variant instantaneous meltwater 18O isotope values overestimated the meltwater contribution by only 1.5 %. These discrepancies highlight the importance of choosing the appropriate endmember isotopes in IHS. The large differences in meltwater contribution for a 2-week peak discharge period based on different endmembers can lead to different interpretations of hydrological, ecohydrological, and biogeochemical processes. Thus, to better understand streamflow generation processes, we suggest using rolling runoff-corrected meltwater 18O or 2H isotope values in the IHS. In the absence of meltwater samples, the 18O or 2H isotope values of snowpack samples during the peak melt season may provide reasonable estimates of the meltwater contribution, with some minor underestimations. Our study highlights the importance of appropriate event meltwater endmember selection and sampling methodology for the IHS.
Meltwater
Snowmelt
Snowpack
δ18O
Cite
Citations (4)
As part of a glacier hydrological study electrical conductivity of meltwaters from two subpolar glaciers was investigated. The dissolved load of a melt stream reflects the mixing, in varying proportions through time, of waters with different chemical characteristics from different environments (Collins, 1977). Conductivity, a surrogate measure of the concentration af total dissolved solids, was used as an indicator af the nature af subglacial and englacial hydrochemical environments and of different meltwater routings through the glaciers. The investigation was carried out at Qamanârssup sermia, an outlet glacier from the Inland Ice, in 1981 and at Kitdlerssuaq, on an outlet glacier from a local ice cap, in 1982 and 1983 (fig. 45). All conductivity values are reported at the measuring temperature, i.e. 0-2°C for glacier meltwater.
Meltwater
Glacier morphology
Glacier ice accumulation
Tidewater glacier cycle
Cite
Citations (3)
Translatory flow is observed in a ground water runoff during a rainstorm. Layered snow cover is considered to play the same role as soil layer for water runoff. The purpose of this paper is to report the translatory flow phenomena of snow meltwater in a snowpack. Studies on the snowmelt runoff in a snowpack were carried out at eastern Canada and Hokkaido. In the case of Canada, the hydrograph of snowmelt is separated into "old water" (meltwater in the lower snowpack) and "new water" (meltwater percolated from surface snow layer) by the concentration of NO3-. The concentration of NO 3- in meltwater in the lower snowpack is estimated to be higher than that in meltwater generated from the surface snow layer. Separated "old water" is the major component of early snowmelt runoff during a day. This quick response of the meltwater in the lower snowpack requires a translatory flow mechanism in the snowpack. "New water" is the major component of the recession limb of the hydrograph. The same phenomena were observed at Moshiri, Hokkaido, during the 1988 snowmelt. Two peaks on the meltwater hydrograph were observed. The first peak is composed of the meltwater in the lower snowpack; the major component of the second peak is the meltwater percolated from the surface snow layer. The translatory phenomenon in a snowpack is not observed when the depth of snow cover is not so thick.
Meltwater
Snowpack
Snowmelt
Cite
Citations (2)
The primary cause of the large landslide in Hachimantai, Akita Prefecture on May 11, 1997 is considered to be heavy rainfall of 110 mm/day on the 8 th three days prior to the landslide. However, the occurrence of this landslide cannot be explained by this rainfall alone because such events occur every 7 to 8 years, according to the Gambel-Chow method for the last 19 years meteorological data. In addition to the heavy rainfall, continuously supplied meltwater from snow pack is also thought to have played an important role in the occurrence of this landslide. Therefore, we estimated the rate of meltwater flow by the heat balance method using the AMeDAS data set of the Meteorological Agency to clarify the meltwater conditions prior to the landslide. Our calculations showed that the 30-50 mm/day of meltwater in late April rose to 40-60 mm/day in the beginning of May due to the seasonal increase of heat fluxes. On May 8, 170 mm of water which consisted of 110 mm of rainfall and 60 mm of meltwater was assumed to have flowed out from the snow pack to the ground. As a result of calculations of meltwater for 19 years and subsequent comparision between meltwater and rainfall of each year and analysis of probable distribution of the annual maximum daily values, it was revealed that the 170 mm of [meltwater+rainfall] flow on May 8 occurs only once every 70-80 years.
Meltwater
Cite
Citations (4)
Meltwater
Cite
Citations (7)
Glaciers are decaying due to global warming. Svalbard is a very sensitive area within the European High Arctic and studies on glacier changes and evolutions are representative for the Arctic. The present work aims glaciers at Spitsbergen; we investigated meltwater supplied by glacierized basins in introducing radioactive isotope measurements in combination with classical parameters. Among the natural radioactive elements, the most promising is the noble gas radon, more precisely the isotope 222Rn, with a short half life of 3.8 days and the possibility of automated continuous measurements. Measurements of radon in glacier meltwater showed surprisingly high concentrations thus enabling investigations with radon as valuable tracer. Only meltwater in contact with rock or sediments has the possibility to be charged with radon. Varying radon concentrations can be linked to changes in mixing meltwater from different origins, roughly the surface of glaciers (supraglacial), within (englacial) and under ice (subglacial). We are able to collect information on the glacier drainage system and its evolution over time and thus contribute to the study of glacier dynamics. Results from three sampling periods on Werenskioldbreen glacier, covering different glaciological seasons, are presented and discussed in this study. The potential results of further continuous measurements will give supplementary information on drainage footpaths and the style and system of the draining of glaciers. Our study intends also a better understanding of the response of glaciers to environmental parameters and, on a longer term, to make a contribution to climate change studies.
Meltwater
Tidewater glacier cycle
Glacier ice accumulation
Rock glacier
Glacier morphology
Glacier mass balance
Cite
Citations (26)
This review manuscript addresses hydro-meteorological correlations of various glaciers situated in the Himalayan region. Meteorological parameters influence the discharge pattern of the glacier. A strong correlation has been observed between discharge and air temperature of the studied Himalayan glaciers. Whereas, other meteorological parameters such as wind speed and wind direction etc. were not significantly correlated with the meltwater runoff of different glaciers in this region. In general, variability (Cv) in discharge from the various Himalayan glaciers such as Chhota Shigri and Gangotri glaciers follow the variability (Cv) in the temperature of these glaciers. Maximum variability (Cv) in meltwater runoff from the Chhota Shigri glacier has been reported in the month of September, which might be due to the fast decline in stream runoff and air temperature of the study area during the month of September. A strong relationship has been observed between suspended sediment concentration and temperature of the majority of studied Himalayan glaciers. Such type of result shows that the suspended sediment concentration in the glacial meltwater has increased with rising air temperature in this region.
Meltwater
Glacier morphology
Cite
Citations (0)
The impact of global warming on the water cycle can be extremely complex and diverse. The results of research summarized below illustrate the scale and the geography of the components' possible changes on a global, regional and local level due to global warming. The changes of air temperature, precipitation, river runoff, evapotranspiration and soil moisture are analyzed on different stages of warming. The results are a base for estimating the reaction of the hydrological regime of large river basin-large inner reservoirs systems. The different reactions of large river basins and of large inner reservoirs on different stages of warming and in different parts of the world are demonstrated.
Water cycle
Global Change
Cite
Citations (4)