Multi-decadal mass balance series of three Kyrgyz glaciers inferred from modelling constrained with repeated snow line observations

Glacier surface mass balance observations in the Tien Shan and Pamir are relatively sparse and often discontinuous. Nevertheless, glaciers are one of the most important components of the high-mountain cryosphere in the region as they strongly influence water availability in the arid, continental and intensely populated downstream areas. This study provides reliable and continuous surface mass balance series for selected glaciers located in the Tien Shan and Pamir-Alay. By cross-validating the results of three independent methods, we reconstructed the mass balance of the three benchmark glaciers, Abramov, Golubin and Glacier no. 354 for the past 2 decades. By applying different approaches, it was possible to compensate for the limitations and shortcomings of each individual method. This study proposes the use of transient snow line observations throughout the melt season obtained from satellite optical imagery and terrestrial automatic cameras. By combining modelling with remotely acquired information on summer snow depletion, it was possible to infer glacier mass changes for unmeasured years. The model is initialized with daily temperature and precipitation data collected at automatic weather stations in the vicinity of the glacier or with adjusted data from climate reanalysis products. Multi-annual mass changes based on high-resolution digital elevation models and in situ glaciological surveys were used to validate the results for the investigated glaciers. Substantial surface mass loss was confirmed for the three studied glaciers by all three methods, ranging from -0.30±0.19 to -0.41±0.33mw.e. yr-1 over the 2004-2016 period. Our results indicate that integration of snow line observations into mass balance modelling significantly narrows the uncertainty ranges of the estimates. Hence, this highlights the potential of the methodology for application to unmonitored glaciers at larger scales for which no direct measurements are available.Publisher PDFPeer reviewe

Изменения ледника Абрамова (Алайский хребет) c 1850 по 2014 г.

The purpose of this study was to determine the nature and rate of changes of the Abramov glacier over the period from 1850 to 2014. The glacier is located on the Alay Ridge in Kyrgyzstan. Its borders were estimated by means of interpretation and analysis of space images from the satellites Landsat-2, 5, 7, 8, KH-4А and KH-9 (program Corona), Geoеye-1 together with aerial photographs and topographical maps, and with addition of results of the field survey of the glacier’s tongue by GPS instruments. As a result, we could find that the longstanding degradation of the glacier continued over the whole period under investigation, and against the background of that there were periods of relative stabilization of the front of the tongue as well as the periods of the glacier advances of different duration and intensity. In 1850, the total area of the glacier accounted for 26.4 km2, but by 2014 it reduced by 3.65 km2, or 13.8%, and became equal to 22.75 km2. Thus, annual reduction of the glacier area was equal approximately to 0.02 km2 per a year, and its length decreased by almost 2950 m, i.e., the glacier contracted, on the average, by 18 m per a year. It should be noted that changes of the glacier area were similar during both the initial and final periods of observations, and it means that no intensification of anthropogenic impact upon the glacier was observed. Obviously, this fact is indicative of the prevalence of natural factors in the change of the glacier, expressed in irregular duration of cyclic changes.Цель данного исследования  – определить характер и скорость изменения ледника Абрамова. Методика определения границ ледника за 1850–2014  г. предусматривала дешифрирование и анализ космических снимков спутников Landsat-2, 5, 7, 8, KH-4А, KH-9 программы Corona, Geoеye-1, аэрофотоснимков и топографических карт, а также съёмку в полевых условиях границ языка ледника с помощью GPS-приборов. В эти годы продолжалась деградации ледника Абрамова, его площадь сократилась на 3,65 км2, т.е. на 13,8%. Средняя скоростью сокращения площади ледника составила около 0,02 км2/год

Re-establishing glacier monitoring in Kyrgyzstan and Uzbekistan, Central Asia

Glacier mass loss is among the clearest indicators of atmospheric warming. The observation of these changes is one of the major objectives of the international climate monitoring strategy developed by the Global Climate Observing System (GCOS). Long-term glacier mass balance measurements are furthermore the basis for calibrating and validating models simulating future runoff of glacierised catchments. This is essential for Central Asia, which is one of the driest continental regions of the Northern Hemisphere. In the highly populated regions, water shortage due to decreased glacierisation potentially leads to pronounced political instability, drastic ecological changes and endangered food security. As a consequence of the collapse of the former Soviet Union, however, many valuable glacier monitoring sites in the Tien Shan and Pamir Mountains were abandoned. In recent years, multinational actors have re-established a set of important in situ measuring sites to continue the invaluable long-term data series. This paper introduces the applied monitoring strategy for selected glaciers in the Kyrgyz and Uzbek Tien Shan and Pamir, highlights the existing and the new measurements on these glaciers, and presents an example for how the old and new data can be combined to establish multi-decadal mass balance time series. This is crucial for understanding the impact of climate change on glaciers in this region

Glaciation of northern slopes of Turkestan and Alai Ranges and its present-day dynamics

Special features of development and existence of present-day glaciation of the Turkistan and Alay ridges are being examined in current climate change. It is found that the main climate elements – air temperature and atmospheric precipitations tend to rise in the highland zones of these ridges. Though, an air temperature rose more intensively than in Inner Tien-Shan, and glacier degradation rates are more intensive here. For 33–43 years, the glaciers of five river basins reduced in its area extent for more than 20%. An increase of a number of glaciers is characteristically under classification of more large ones. Small glaciers sited rather in low hypsometrical levels, are quite disappeare

Changes of the Abramov Glacier (Alay Ridge) from 1850 to 2014

The purpose of this study was to determine the nature and rate of changes of the Abramov glacier over the period from 1850 to 2014. The glacier is located on the Alay Ridge in Kyrgyzstan. Its borders were estimated by means of interpretation and analysis of space images from the satellites Landsat-2, 5, 7, 8, KH-4А and KH-9 (program Corona), Geoеye-1 together with aerial photographs and topographical maps, and with addition of results of the field survey of the glacier’s tongue by GPS instruments. As a result, we could find that the longstanding degradation of the glacier continued over the whole period under investigation, and against the background of that there were periods of relative stabilization of the front of the tongue as well as the periods of the glacier advances of different duration and intensity. In 1850, the total area of the glacier accounted for 26.4 km2, but by 2014 it reduced by 3.65 km2, or 13.8%, and became equal to 22.75 km2. Thus, annual reduction of the glacier area was equal approximately to 0.02 km2 per a year, and its length decreased by almost 2950 m, i.e., the glacier contracted, on the average, by 18 m per a year. It should be noted that changes of the glacier area were similar during both the initial and final periods of observations, and it means that no intensification of anthropogenic impact upon the glacier was observed. Obviously, this fact is indicative of the prevalence of natural factors in the change of the glacier, expressed in irregular duration of cyclic changes

Mass-balance reconstruction for Glacier No. 354, Tien Shan, from 2003 to 2014

This study presents a reconstruction of the seasonal mass balance of Glacier No. 354, located in the Akshiirak range, Kyrgyzstan, from 2003 to 2014. We use a distributed accumulation and temperature-index melt model driven by daily air temperature and precipitation from a nearby meteorological station. The model is calibrated with in situ measurements of the annual mass balance collected from 2011 to 2014. The snow-cover depletion pattern observed using satellite imagery provides additional information on the dynamics of mass change throughout the melting season. Two digital elevation models derived from high-resolution satellite stereo images acquired in 2003 and 2012 are used to calculate glacier volume change for the corresponding period. The geodetic mass change thus derived is used to validate the modelled cumulative glacier-wide balance. For the period 2003–12 we find a cumulative mass balance of –0.40∓10 m w.e. a–1. This result agrees well with the geodetic balance of –0.48∓0.07 m w.e. a–1 over the same period

Оледенение северных склонов Туркестанского и Алайского хребтов и его современная динамика

Special features of development and existence of present-day glaciation of the Turkistan and Alay ridges are being examined in current climate change. It is found that the main climate elements – air temperature and atmospheric precipitations tend to rise in the highland zones of these ridges. Though, an air temperature rose more intensively than in Inner Tien-Shan, and glacier degradation rates are more intensive here. For 33–43 years, the glaciers of five river basins reduced in its area extent for more than 20%. An increase of a number of glaciers is characteristically under classification of more large ones. Small glaciers sited rather in low hypsometrical levels, are quite disappearedРассматриваются особенности развития оледенения северных склонов Туркестанского и Алайского хребтов в условиях современного изменения климата. В высокогорных зонах этих хребтов c середины ХХ до начала ХХI в. отмечается тенденция к повышению температуры воздуха и росту количества атмосферных осадков. Температура воздуха повышается здесь интенсивнее, чем во Внутреннем Тянь-Шане, поэтому и темпы деградации ледников в этом районе выше. За 1965–2000 гг. площади ледников пяти речных бассейнов сократились здесь более чем на 20%. В результате распада ледников общее их число увеличилось. Небольшие ледники, расположенные на относительно низких гипсометрических уровнях, исчезли совсем.

Evaluating the timing of former glacier expansions in the Tian Shan: A key step towards robust spatial correlations

The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in 10Be surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 28 ka during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia