Change in the extent of glaciers and glacier runoff in the Chinese sector of the Ile River Basin between 1962 and 2012

Change in glacier area in the Kuksu and Kunes river basins, which are tributaries to the internationally important Ile River, were assessed at two different time steps between 1962/63, 1990/93, and 2010/12. Overall, glaciers lost 191.3 ± 16.8 km2 or 36.9 ± 6.5% of the initial area. Glacier wastage intensified in the latter period: While in 1962/63–1990/93 glaciers were losing 0.5% a−1, in 1990/93–2010/12, they were losing 1.2% a−1. Streamflow of the Ile River and its tributaries do not exhibit statistically significant change during the vegetative period between May and September. Positive trends were observed in the Ile flow in autumn, winter, and early spring. By contrast, the calculation of the total runoff from the glacier surface (including snow and ice melt) using temperature-index method and runoff forming due to melting of multiyear ice estimated from changes in glacier volume at different time steps between the 1960s and 2010s, showed that their absolute values and their contribution to total river runoff declined since the 1980s. This change is attributed to a strong reduction in glacier area

Impacts of climate change on river discharge in the northern Tien Shan: Results from long-term observations and modelling

This paper presents preliminary results of investigation of the observed and projected changes in discharge of the snow- and glacier-nourished rivers of the Balkhash-Alakol basin, Kazakhstan using the long-term homogeneous records and climate projections from an ensemble of climate simulations. Positive trends in discharge were registered at most sites between the 1950s and 2010s. An increase in discharge was observed at all sites between May and October in 2000 – 2013 in comparison with the previous decades which was particularly strong in July-August at the rivers with a high proportion of glacierized area. This positive trend in discharge appears to be driven primarily by an increase in temperature. Results for four climate scenarios with spatial resolution of 25 km are presented. These scenarios were generated using regional climate model PRECIS driven by HadGEM GCM for RCP 2.6 and RCP 8.5 scenarios, HadCM3Q0 and ECHAM5 GCM for A1B scenario. While all climate experiments project increase in temperature, precipitation projections vary between models, seasons and spatially. HBV-ETH model was used to simulate the observed and future discharge for the Ulken and Kishi Almatinka rivers using climate projections from PRECIS-HadCM3Q0 simulation for A1B scenario. The results show that peak flow has already been reached at both rivers and is likely to continue for the next 10-15 years. A small decrease of 7-10% in annual discharge is projected for the Ulken and Kishi Almatinka for the 2025-2044 period increasing thereafter and the projected decline in discharge is more significant in summer

Assessment of changes in mass balance of the Tuyuksu group of glaciers, northern Tien Shan between 1958 and 2016 using ground-based observations and Pleiades satellite imagery

Continuous measurements of glaciological mass balance have been conducted at the Central Tuyuksu glacier, Tuyuksu group of glaciers, Ile Alatau, northern Tien Shan since 1957 showing that cumulative mass balance was negative since the 1970s. Geodetic mass balance was calculated for the 1958-1998 and 1998-2016 periods using multi-temporal digital elevation models derived from the historic photogrammetric surveys from 1958 and 1998, and the high-resolution Pléiades satellite stereo imagery from 2016. Geodetic measurements revealed a mean surface lowering of 23.2±2.2 m (0.40 ± 0.04 m a-1) and reduction in volume of (67.7±6.7)x106 m3 in 1958-2016 at the Central Tuyuksu glacier yielding a geodetic mass balance of -21.8±2.6 m w.e. Similar trends were observed at other glaciers of the Tuyuksu group which lost in total 83.4x106 m3 of ice. Annual rates of mass balance have not changed significantly from 1958-1998 (-0.39±0.05 m w.e.) to 1998-2016 (-0.35±0.18 m w.e.) at the Central Tuyuksu and at other glaciers of the Tuyuksu group whose maximum elevations exceed 4000 m a.s.l. While glacier thinning intensified in the ablation zone and affected larger area in 1998-2016 extending to 3600-3700 m a.s.l., accumulation increased at higher elevations in 1998-2016. Geodetic mass balance was more negative in 1998-2016 than in 1958-1998 at the smaller glaciers with lower maximum elevations. At the Central Tuyuksu, geodetic mass balance was in close agreement with glaciological mass balance particularly in 1958-1998 when the difference between the geodetic and cumulative glaciological mass balance values did not exceed 5 %. During 1998-2016, this difference increased to 14 % with glaciological method producing more negative mass balance. This discrepancy was attributed to a systematic bias introduced by the lack of stakes in the accumulation zone of Central Tuyuksu whose contribution to uncertainty increased in 1998-2016 in line with an increase in accumulation. Negative mass balance of the Tuyuksu group of glaciers was attributed to continuing increase in summer temperatures and low accumulation observed in the 1970s-1980s and at the turn of the century

The hydrochemistry and water quality of glacierized catchments in Central Asia: a review of the current status and anticipated change

Study focus The literature on hydrochemistry and water quality was reviewed to identify gaps in knowledge required to understand and quantify the impacts of climate change and deglacierization. New hydrological insights for the region The main knowledge gap was the characterization of hydrochemistry and water quality along the elevation continuum from glaciers to arid plains. The chemical composition of snow and glacier ice are understood relatively well but the pathways of pollutants stored in glacier ice and released with melt into the aquatic systems are not researched. There is a lack of publications on the release of organic carbon following deglacierization and element leaching from the exposed substrate, permafrost and rock glaciers. Snow and glacial melt dilutes pollutants along the river channels, reducing concentrations and mostly ensuring the compliance with water quality standards including downstream locations. Poor surface water quality is associated with irrigation, the practice of soil washing, and discharge of the untreated sewage. There is a notable lack of information about the links between snow and glacier melt, aquifer recharge and groundwater quality and this is a major gap in knowledge affecting environmental and health protection. Better understanding and quantification of factors and processes controlling hydrochemistry and water quality is needed to adapt to the impacts of the imminent deglacierization

Emptying Water Towers? Impacts of Future Climate and Glacier Change on River Discharge in the Northern Tien Shan, Central Asia

Impacts of projected climate and glacier change on river discharge in five glacierized catchments in the northern Tien Shan, Kazakhstan are investigated using a conceptual hydrological model HBV‐ETH. Regional climate model PRECIS driven by four different GCM‐scenario combinations (HadGEM2.6, HadGEM8.5, A1B using HadCM3Q0 and ECHAM5) is used to develop climate projections. Future changes in glaciation are assessed using the Blatter–Pattyn type higherorder 3D coupled ice flow and mass balance model. All climate scenarios show statistically significant warming in the 21st Century. Neither projects statistically significant change in annual precipitation although HadGEM and HadCM3Q0‐driven scenarios show 20–37% reduction in July–August precipitation in 2076–2095 in comparison with 1980–2005. Glaciers are projected to retreat rapidly until the 2050s and stabilize afterwards except under the HadGEM8.5 scenario where retreat continues. Glaciers are projected to lose 38–50% of their volume and 34–39% of their area. Total river discharge in July–August, is projected to decline in catchments with low (2–4%) glacierization by 20–37%. In catchments with high glacierization (16% and over), no significant changes in summer discharge are expected while spring discharge is projected to increase. In catchments with medium glacierization (10–12%), summer discharge is expected to decline under the less aggressive scenarios while flow is sustained under the most aggressive HadGEM8.5 scenario, which generates stronger melt

Bathymetries of proglacial lakes: a new data set from the northern Tien Shan, Kazakhstan

Between 2009 and 2020, 74 bathymetric surveys of 57 glacial lakes were conducted in the northern Tien Shan using the ecosounding technique. The surveys provided data on lake depths and other parameters characterising the three-dimensional lake geometry, and bathymetrically derived lake volumes. The sample included 21 glacier-connected lakes, 27 lakes formed on the young moraines without connection with glacier tongue, eight lakes formed on the older moraines and one rock-dammed lake. The lakes’ volumes ranged between 0.029x105 and 53.89x105 m3 with the largest value of mean depth was 23 m. There is a statistically significant correlation between lake depth and width, length and area, best approximated by the power, linear, and polynomial models, with coefficients of determination ranging between 0.50 and 0.78 for the glacier-connected lakes. The power equations underestimated both depths and volumes of larger lakes but the second-order polynomial model provided a closer approximation in the study region. The obtained data were combined with the bathymetrically derived depth and volume data published in the literature extending the global data set of bathymetries of lakes with natural dams. The area-depth scaling equations derived from the combined data set showed a considerable improvement in correlation between area and depth in comparison with the earlier studies. The measured bathymetries of the glacier-connected lakes were compared with bathymetries of the same lakes simulated using GlabTOP2 model and published simulated ice thickness data. There is generally a good agreement between the measured and simulated bathymetries although GlabTOP2 tends to overestimate lake depths. The data from the bathymetric surveys and GlabTOP2 model are used by the practitioners to reduce and avoid risks associated with glacier lake outburst floods and are important instruments of the regional strategy of adaptation to climate change

Cryosphere and land cover influence on stream water quality in Central Asia's glacierized catchments

This work helps address recent calls for systematic water quality assessment in Central Asia and considers how nutrient and salinity sources, and transport, affect water quality along the continuum from the cryosphere to the lowland plains. Spatial and, for the first time, temporal variations in stream water pH, temperature, electrical conductivity, and nitrate and phosphate concentrations are presented for four catchments (485–13,500 km2), all with glaciers and major urban areas. The catchments studied were: Kaskelen (Kazakhstan), Ala-Archa (Kyrgyzstan), Chirchik (Uzbekistan) and the Kofarnihon (Tajikistan). Measurements were made in cryosphere, stream water, groundwater, reservoir and lake samples over a 22-month period at fortnightly intervals from 35 sites. The results highlight that glacier, permafrost and rock glacier outflows were primary and secondary nitrate sources (>1 mg N L−1) to the headwaters, and there were major increases in salinity and nitrate concentrations where rivers receive inputs from agriculture and settlements. Overall, the water quality complied with national and World Health Organization standards, however there were pollution hot-spots with shallow urban groundwaters contaminated with nitrate (>11 mg N L−1) and stream electrical conductivity above 800 μS cm−1 in some agricultural areas indicative of high salinity. Phosphate concentrations were generally low (0.2 mg P L−1) in urban areas due to effluent contamination. A melt water dilution effect along the main river channels was discernible, in the electrical conductivity and nitrate concentration seasonal dynamics, 100 s of km from the headwaters. Thus, the input of relatively clean water from the cryosphere is an important regulator of main channel water quality in the urban and farmed lowland plains adjacent to the Tien Shan and Pamir. Improved sewage treatment is needed in urban areas

Boost glacier monitoring

Glacier-mass changes are a reliable indicator of climate change. On behalf of the worldwide network of glacier observers, we urge parties to the United Nations Framework Convention on Climate Change to boost international cooperation in monitoring these changes, and to include the results in the Paris agreement’s global stocktake. Since 1960, glaciers have lost more than 9,000 gigatonnes of ice worldwide — the equivalent of a 20-metre-thick layer with the area of Spain. This melting alone — as distinct from that of the Greenland and Antarctic ice sheets — has raised global sea level by almost 3 centimetres, contributing 25–30% of the total rise (M. Zemp et al. Nature 568, 382–386; 2019). The present rate of melting is unprecedented. Several mountain ranges are likely to lose most of their glaciers this century. And we face the loss of almost all glaciers by 2300 (B. Marzeion et al. Cryosph. 6, 1295–1322; 2012). Glacier shrinkage will severely affect freshwater availability and increase the risk of local geohazards. Global sea-level rise will result in the displacement of millions of people in coastal regions and in the loss of life, livelihoods and cultural- heritage sites. The systematic monitoring of glaciers has been internationally coordinated for 125 years. Continuing to do so will document progress in limiting climate change for current and future generations

Historically unprecedented global glacier changes in the 1 early 21st century

Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (∼42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (∼5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.Fil: Zemp, Michael. Universitat Zurich; SuizaFil: Frey, Holger. Universitat Zurich; SuizaFil: Gärtner-Roer, Isabelle. Universitat Zurich; SuizaFil: Nussbaumer, Samuel U.. Universitat Zurich; SuizaFil: Hoelzle, Martin. Universite de Fribourg; Suiza. Universitat Zurich; SuizaFil: Paul, Frank. Universitat Zurich; SuizaFil: Haeberli, Wilfried. Universitat Zurich; SuizaFil: Denzinger, Florian. Universitat Zurich; SuizaFil: Ahlstrøm, Andreas P.. Geological Survey Of Denmark And Greenland; DinamarcaFil: Anderson, Brian. Victoria University Of Wellington; Nueva ZelandaFil: Bajracharya, Samjwal. International Centre For Integrated Mountain Development; NepalFil: Baroni, Carlo. Università degli Studi di Pisa; ItaliaFil: Braun, Ludwig N.. Bavarian Academy Of Sciences; AlemaniaFil: Càceres, Bolívar E.. Instituto Nacional de Meteorología E Hidrología; EcuadorFil: Casassa, Gino. Universidad de Magallanes; ChileFil: Cobos, Guillermo. Universidad Politécnica de Valencia; EspañaFil: Dàvila, Luzmila R.. Unidad de Glaciología y Recursos Hídricos; PerúFil: Delgado Granados, Hugo. Universidad Nacional Autónoma de México; MéxicoFil: Demuth, Michael N.. Natural Resources Canada; CanadáFil: Espizua, Lydia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Fischer, Andrea. Osterreichische Akademie Der Wissenschaften; AustriaFil: Fujita, Koji. Nagoya University; JapónFil: Gadek, Bogdan. University Of Silesia; PoloniaFil: Ghazanfar, Ali. Global Change Impact Studies Centre; PakistánFil: Hagen, Jon Ove. University of Oslo; NoruegaFil: Holmlund, Per. Stockholms Universitet; SueciaFil: Karimi, Neamat. Ministry of Energy; IránFil: Li, Zhongqin. Chinese Academy of Sciences; República de ChinaFil: Pelto, Mauri. Nichols College; Estados UnidosFil: Pitte, Pedro Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Popovnin, Victor V.. Moscow State University; RusiaFil: Portocarrero, Cesar A.. Unidad de Glaciología y Recursos Hídricos; PerúFil: Prinz, Rainer. Universidad de Innsbruck; AustriaFil: Sangewar, Chandrashekhar V.. Geological Survey of India; IndiaFil: Severskiy, Igor. Institute Of Geography; KazajistánFil: Sigurdsson, Oddur. Icelandic Meteorological Offic; IslandiaFil: Soruco, Alvaro. Universidad Mayor de San Andrés; BoliviaFil: Usubaliev, Ryskul. Central Asian Institute For Applied Geosciences; KirguistánFil: Vincent, Christian. Laboratory of Glaciology and Environmental Geophysics; Franci