Changes In Equilibrium Line Altitude Research Articles

Reconstructions of Little Ice Age glaciers and climate in the Tanggula Mountains, Central Tibet Plateau

Mountain glaciers are one of the most sensitive indicators of climate change. Reconstructing past glacier extents provides valuable insights into the climate change for specific regions where instrumental records are not enough and even absent. In the paper we mapped the outlines for 691 Little Ice Age (LIA) glaciers in terms of prominent moraines beyond contemporary glaciers in the Tanggula Mountains, central Tibetan Plateau (TP). Based on these glacier outlines, we reconstructed the ice thicknesses and surfaces for the LIA glaciers in the region. Accordingly, we calculated the equilibrium-line altitudes (ELAs) for contemporary and LIA glaciers. By comparing the ELAs between the contemporary and LIA glaciers, we estimated the LIA summer temperature decreases in different subregions of the Tanggula Mountains. Since the LIA, the ELA have risen by 35.6 ± 18.8 m, 26.1 ± 17.6 m, and 63.1 ± 38.6 m in the respective western, central, and eastern subregions of the Tanggula Mountains. Assuming no change in precipitation, the LIA summer temperature would decrease by 0.22 ± 0.12 °C, 0.14 ± 0.09 °C, and 0.34 ± 0.21 °C in the three subregions, respectively. Moreover, glaciers in the western, central, and eastern subregions have lost 13.3%, 23.9%, and 42.8% of their area, 15.4%, 25.3%, and 39.6% of their length, and 20.8%, 39.0%, and 61.0% of their volume, respectively. By compiling the LIA ELA data from previous studies, we also estimated the LIA summer temperature changes for other regions of the TP. The LIA ELA and summer temperature changes relative to the present showed a decreasing trend from the edges towards the interior on the TP.

Last Glacial Maximum and subsequent glacial chronology in the monsoon-dominated Sikkim Himalaya, India

The study investigates sequential evolution of glacial-landforms in relation to paleo-climate by establishing glacial chronology in Zemu and East-Rathong Glaciers valleys, Sikkim, Eastern Himalaya during the Late-Quaternary. This region is dominated by the Indian summer monsoon, followed by winter rain from the NE-monsoon and Westerlies which influence the glaciers. The study relies on field-based geomorphological mapping and geospatial datasets. The Toe-to-Headwall Altitude Ratio, Toe-to-Summit Altitude Method, and Maximum Elevation of Lateral Moraines methods have been used to calculate the equilibrium line altitudes (ELA) to assess magnitudes of glacial changes over time. OSL dating is used to assess the timing of glacial stages. Additionally, a comparison is made with ELA changes, the distance of moraines from the present glacier snouts, and established glacial chronologies in neighboring areas. The existing landscape depicts the dominant role of the region's present and past glacial processes. The region is also modified by periglacial, paraglacial, and fluvial processes. Four glacial stages have been identified in the region during the late-Quaternary period, contemporaneous to the Last Glacial Maximum, Younger Dryas, Late-Holocene, and Little Ice Age. The first stage (Sikkim-I), marked by dissected trimlines up to ∼16 km downstream, appears to belong to the global Last Glacial Maximum and dated to ∼18.276 ± 0.589 ka with a change of −519.5 m and − 3.4 °C in ELAs and temperature, respectively. The second stage, Sikkim-II is represented by lateral moraines running up to ∼5 km downstream in U-shaped valleys and seems to coincides with the Younger Dryas with ELAs depression of −261.8 m along with a − 1.7 °C drop in temperature. The third Stage (Sikkim-III), marked by small pairs of stable lateral moraines covered with shrubs within ∼3 km downstream, probably belongs to the late Holocene when ELAs and temperature dropped by −177.3 m and − 1.2 °C, respectively. The fourth stage (Sikkim-IV) is notified by a dumped heap of end moraines within ∼2 km downstream, possibly occurred during the LIA with a depression of −72.4 m in ELAs and − 0.5 °C in temperature. These glacial stages are synchronous with the glaciations in the neighboring regions of Thangu in north-Sikkim, Bhutan, and eastern Himalaya syntax. However, the findings of the study differ from the westerly dominated NW Himalayas, broadly.

Response of the Thick and Thin Debris-Covered Glaciers between 1971 and 2019 in Ladakh Himalaya, India—A Case Study from Pensilungpa and Durung-Drung Glaciers

This paper aims to broadly understand the response of glaciers to thick and thin debris cover from one of the less explored regions (Zanskar) of the Himalaya. The present study is based on ground-based measurements (from 2015 to 2019), satellite data (since 1971), and available topographic maps (at a 1:50,000 scale). The study includes snout retreat, changes in equilibrium line altitude (ELA), surface elevation, and modeled mass balance of thick and thin debris-covered Pensilungpa (Suru River basin) and Durung-Drung (Doda River basin) glaciers in the western Indian Himalaya, Ladakh, for the past five decades. The Durung-Drung Glacier (DDG) receded ~−624 ± 547 m with an average rate of −12 ± 11 m a−1 between 1971 and 2019. The frontal part of the DDG is broad (~2 km wide), which shows wide discrepancies in its retreat. Compared to DDG, the small and narrow snout of the Pensilungpa Glacier (PG) retreated −270.5 ± 27.5 m (1971 to 2019), with an average rate of −5.6 ± 0.57 m a−1. Similarly, the four years (2015–2019) of field observations suggest that the retreat rate of PG and DDG is −6.7 ± 3 and −18 ± 15 m a−1, and the rate of modeled glacier mass loss is −0.29 ± 0.3 and −0.3 ± 0.3 m w.e. a−1, respectively. Furthermore, the ELA of the DDG and PG between 1971 and 2019 increased by ~59 ± 38 and ~23 ± 19 m, respectively. The change in the longitudinal profile of the glaciers along the centerline between 2000 and 2017 shows the DDG and PG lost ~17 and 15 m surface ice thickness. The change in debris cover plays a critical role in the glacier surface lowering, shrinkage, retreat, and mass balance. Hence, we quantitatively evaluated the influence of the debris cover on summer ablation and terminus recession on two different characteristic glaciers (DDG and PG) with its potential effect on the mass balance process (area-volume loss).

On the Shift of Glacier Equilibrium Line Altitude (ELA) under the Changing Climate

Presently available information on the glacier equilibrium line altitude (ELA) is being collected and examined. The historical course of the world’s longest ELA series of 107 years at the Claridenfirn is reviewed together with climatic elements. Further, the changes in ELAs of 70 glaciers the world over are investigated, and a linear plane model for the speed of the ELA shift is proposed as a function of the changing rates of summer temperature and winter mass balance. The four glaciers in Europe, which diverge most from the plane, are investigated in detail. The cause of the divergence is likely due to be the change in solar global radiation. Although a precise quantification of the role of radiation is not possible at this stage for the entire world, the role of solar radiation is investigated for these glaciers. Globally viewed, ten, or 15% of the 70 investigated glaciers, are expected to lose their accumulation areas within the next ten years. Half of all studied glaciers will follow the same fate by the end of this century under the present climatic conditions. If climate change is accelerated, the disappearance of glaciers will occur sooner than presented in this study.

Little Ice Age climate in southernmost Greenland inferred from quantitative geospatial analyses of alpine glacier reconstructions

Alpine glaciers are sensitive responders to climate fluctuations, especially to changes in summer temperature, and thus their past extents are invaluable indicators of past climate. Here, we leverage geomorphological evidence of past glacier extent to reconstruct the three-dimensional surfaces of 42 land-terminating paleoglaciers in southernmost Greenland and calculate their equilibrium-line altitudes (ELAs) during the presumed coldest interval of the Little Ice Age (LIA). We compare LIA paleoglacier ELAs with observed modern glacier ELAs (i.e. snowlines) to estimate the LIA summer temperature depression relative to present. On average, we find that ELAs rose 122 ± 64 m since the LIA, which corresponds to a summer temperature change of 1.1± 0.6 ° C, assuming no change in precipitation. Because there are minimal constraints on LIA precipitation anomalies in southernmost Greenland, we also report summer temperature changes for precipitation values ranging from a substantially drier to substantially wetter than modern LIA. When compared with independent temperature evidence, our results suggest LIA precipitation was similar to or slightly less than today. The alpine glaciers studied lost (on average) 56± 16% of their area and 44± 13% of their centerline length between the LIA culmination and 2019 CE. In general, smaller and lower elevation glaciers lost larger fractions of their area. We find no clear geographic patterns in the magnitudes of ELA, area, or length changes across the 9000 km2 study area despite its heterogeneous climate. This study demonstrates a workflow for regional-scale paleoglacier reconstruction and provides the first quantitative LIA summer paleotemperature estimate for southernmost Greenland via region-wide glacial evidence. Our work also suggests the need for reconstruction of a large number of glaciers to infer past regional climatic information, as individual glaciers may respond heterogeneously to climate perturbations leading to variable changes in their ELA and length.

Changes in equilibrium-line altitude and implications for glacier evolution in the Asian high mountains in the 21st century

Changes in equilibrium-line altitude and implications for glacier evolution in the Asian high mountains in the 21st century

Palaeoglaciation in the Low Latitude, Low Elevation Tropical Andes, Northern Peru

Characterising glaciological change within the tropical Andes is important because tropical glaciers are sensitive to climate change. Our understanding of glacier dynamics and how tropical glaciers respond to global climate perturbations is poorly constrained. Studies of past glaciation in the tropical Andes have focused on locations where glaciers are still present or recently vacated cirques at high elevations. Few studies focused on lower elevation localities because it was assumed glaciers did not exist or were not as extensive. We present the first geomorphological evidence for past glaciations of the Lagunas de Las Huaringas, northern Peru, at elevations of 3,900–2,600 m a.s.l. Mapping was conducted using remotely-sensed optical imagery and a newly created high-resolution (∼2.5 m) digital elevation model (DEM). The area has abundant evidence for glaciation, including moraines, glacial cirques, hummocky terrain, glacial lineations and ice-sculpted bedrock. Two potential models for glaciation are hypothesised: 1) plateau-fed ice cap, or 2) valley glaciation. Assuming glaciers reached their maximum extent during the Local Last Glacial Maximum (LLGM), between 23.5 ± 0.5 and 21.2 ± 0.8 ka, the maximum reconstructed glacial area was 75.6 km2. A mean equilibrium line altitude (ELA) of 3,422 ± 30 m was calculated, indicating an ELA change of −1,178 ± 10 m compared to modern snowline elevation. There is an east to west ELA elevation gradient, lower in the east and higher in the west, in-line with modern day transfer of moisture. Applying lapse rates between 5.5 and 7.5°C/km provides a LLGM temperature cooling of between 6.5–8.8°C compared to present. These values are comparable to upper estimates from other studies within the northern tropical Andes and from ice-core reconstructions. The mapping of glacial geomorphology within the Lagunas de las Huaringas, evidences, for the first time, extensive glaciation in a low elevation region of northern Peru, with implications for our understanding of past climate in the sub-tropics. Observations and reconstructions support a valley, rather than ice cap glaciation. Further work is required to constrain the timing of glaciations, with evidence of moraines younger than the LLGM up-valley of maximum glacier extents. Numerical modelling will also enable an understanding of the controls of glaciation within the region.

Debris Emergence Elevations and Glacier Change

Debris-covered glaciers represent potentially significant stores of freshwater in river basins throughout High Mountain Asia (HMA). Direct glacier mass balance measurements are extremely difficult to maintain on debris-covered glaciers, and optical remote sensing techniques to evaluate annual equilibrium line altitudes (ELAs) do not work in regions with summer-accumulation type glaciers. Surface elevation and glacier velocity change have been calculated previously for debris-covered glaciers across the region, but the response of debris cover itself to climate change remains an open question. In this research we propose a new metric, i.e. the debris emergence elevation (ZDE), which can be calculated from a combination of optical and thermal imagery and digital elevation data. We quantify ZDE for 975 debris-covered glaciers in HMA over three compositing periods (1985–1999, 2000–2010, and 2013–2017) and compare ZDE against median glacier elevations, modelled ELAs, and observed rates of both mass change and glacier velocity change. Calculated values of ZDE for individual glaciers are broadly similar to both median glacier elevations and modelled ELAs, but slightly lower than both. Across the HMA region, the average value of ZDE increased by 70 +/− 126 m over the study period, or 2.7 +/− 4.1 m/yr. Increases in ZDE correspond with negative mass balance rates and decreases in glacier velocity, while glaciers and regions that show mass gains and increases in glacier velocity experienced decreases in ZDE. Regional patterns of ZDE, glacier mass balance, and glacier velocities are strongly correlated, which indicates continued overall increases in ZDEE and expansion of debris-covered areas as glaciers continue to lose mass. Our results suggest that ZDE is a useful metric to examine regional debris-covered glacier changes over decadal time scales, and could potentially be used to reconstruct relative mass and ELA changes on debris-covered glaciers using historical imagery or reconstructed debris cover extents.

Current glacier status and ELA changes since the Late Pleistocene in the Hindu Kush Mountains of Afghanistan

• In the HKM, Afghanistan ELA shows less change from Late Pleistocene to the present. • Climate change impacts different sizes of glaciers differently. • Other than climate, slope and elevation can define the recession of glaciers. • Increase in volume and number of glacial lakes is on rise in the HKM, Afghanistan. The glacier cover of the Hindu Kush Mountains of Afghanistan provides a natural laboratory to assess the impact of climate change on the cryosphere. However, to date, not much is known about how the cryosphere in these mountainous regions is responding to climate change. Therefore, using an integrated approach including geospatial technology, climate data, a mass balance study, as well as topographic analysis, we present the first systematic study of glacier fluctuations in the Kokcha sub-basin of the Afghanistan Range for the last 25 years (1990 to 2015). The glacier cover and the number of glaciers in the basin have reduced from 576 km 2 and 1007 in 1990 to 492 km 2 and 998 in 2015 respectively, losing ~84 km 2 (~15%) of the total glaciated area. Besides the mass loss of the glaciers ranges from −0.65 m water equivalent per year and −0.02 m water equivalent per year with an average of −0.20 m water equivalent per year as estimated by the geodetic method. The equilibrium line altitude changes since the Late Pleistocene to the present vary from 810 ± 145 m to 1060 ± 145 m with an average of 722 ± 145 m. The increasing trend of temperature and shifting precipitation seasons have resulted in enhanced glacier recession and the formation of numerous glacial lakes in the basin. In addition to the climatic variables and glacier size, the topographic parameters slope, and elevation are observed to be the dominant factors influencing glacier recession and mass changes in the basin.

Late Quaternary glacial advances and equilibrium-line altitude changes in a semi-arid region, Suru Basin, western Himalaya

This study examines the late Quaternary glacial history of Suru Basin and its associated tributary valleys (i.e., Achambur, Kangriz, Shafat, Rangdum, and Pensilugnpa), western Himalaya, based on the data collected from field surveys (2015–2019), satellite images, and optically stimulated luminescence (OSL) dating. The glaciers in Suru Basin have fluctuated greatly throughout the Marine Isotope Stages (MIS) 3 and 2 to the Little Ice Age (LIA), and are critical in understanding the linkages between regional and global climate change. Here, we present a detailed record of five major glacial advances of decreasing magnitude, dated 33–23 ka, 16 ka, 13–11 ka, 10–7.3 ka, 2.8–2.3 ka, and a minor advance dated 0.7–0.4 ka. These five major glacial advances are named from oldest to youngest as Suru-I to V, based on their optical chronology, geographical position, moraine stratigraphy, and glacially polished rock surfaces. Whereas, the equilibrium-line altitude (ELA) ascended by ∼538 m from the oldest glacial advance (Suru-I) to the present-day, followed by four other events (Suru-II, III, IV, and V) with ascended ELAs of ∼522, ∼399, ∼243, and 215 m, respectively. Suru Basin has lost ∼502 km2 in its glaciated area and ∼163 km3 in ice volume from Suru-I to the present-day. The magnitude of glacier extent decreased from the MIS 3 and 2, early to late-Holocene, and LIA. The timing of these glacial advances is coarsely in agreement with North Atlantic millennial-scale climate oscillations (Heinrich events), signifying the probable correlation between these abrupt climate changes and glacial fluctuations in this semi-arid region of the Himalaya.

Glacial geomorphology and recent glacial recession of the Harmukh Range, NW Himalaya

A comprehensive description of the glaciation and glacial geomorphology of the Harmukh range, northwest Himalaya is reported first time in this study. The geomorphic system of the range is dominated by glaciation and provides an excellent opportunity to assess the glacial fluctuations from the Late Quaternary to the present. Using a time series of the satellite data from 1992 to 2018, the glacier area, snout and equilibrium line altitude (ELA) changes of the existing glaciers in the Harmukh Range were estimated. The glacier cover has receded from 7.47 ± 0.58 km2 in 1992 to 6.24 ± 0.62 km2 in 2018, a deglaciation of 16.46 ± 0.24%. The glaciers showed an upward shift in ELA from 47 m to 80 m during the last two and a half decade. The observations revealed that, other than the climatic factors, the ELA change and glacier recessions are influenced by the glacier size, mean altitude, and the aspect of the glaciers. Further, the high-resolution Google Earth images, supplemented by field observations, were used for mapping various glacial-geomorphic landforms. The nature of glacial grooves, overdeepenings, the height of the lateral moraine deposits and trimlines indicated appreciable thickness of the former glaciers. The pattern of the glaciated valleys revealed that the area has predominantly experienced alpine type of glaciation with most of the glaciers centred on the Harmukh peak. Based on the shape and the number of lateral moraine ridges present, it is suggested that the area has witnessed three major glacial advances. By tracing the outer limits of the glacial valleys, moraine boulders, and ice scoured terrain, it was estimated that the glaciers in the range covered 629 km2 during the glacial maxima. The presence of numerous rock glaciers and debris-free cirque glaciers on the north-eastern slopes of the range indicated a strong climatic and topographical control on the pattern, situation and extent of glaciers. However, there is a need for detailed field-based mapping of the glacial-geomorphology and geochronological study in order to better understand the nature and extent of paleo-glaciation, the observed glacier recession and the past climatic variations in this hitherto understudied glaciated region of the Kashmir Himalaya.

Climatic controls on the equilibrium-line altitudes of Scandinavian cirque glaciers

The equilibrium-line altitudes (ELAs) of reconstructed palaeoglaciers have been widely used to assess palaeoclimatic conditions, yet this concept has rarely been tested using modern glaciers. To address this shortcoming, correlations between the ELAs of 513 modern cirque glaciers and present-day climatic and topographic variables across Scandinavia, as well as regional trends in ELA and climate, are analysed. ELAs are calculated using the Area-Altitude-Balance-Ratio method, with a ratio of 1.5 ± 0.4. Results indicate that glacier ELAs are strongly correlated with distance from the coast. This reflects the present-day precipitation pattern of the region (characterised by high precipitation near the sea) and demonstrates a climate dominated by a maritime-continental transition. Temperature explains differences in glacier ELA regional trends as well as ELA changes with latitude. Following standard meteorological convention, Scandinavia is divided into two macro-climate regions and analyses are run within the macro-regions as well as the complete dataset. The strength of correlations between ELA and precipitation increases when the study is divided into northern and southern macro-regions. These results test long held assumptions about relationships between climate and cirque glacier ELA, which is of particular relevance to palaeoclimatic studies based on the reconstruction of former cirque glaciers.

Reconstruction of the Little Ice Age glaciers and equilibrium line altitudes in the Kodar Range, southeast Siberia

Little Ice Age (LIA), a time of global cooling widely manifested in the 14th-19th centuries, was characterized by worldwide expansion of mountain glaciers. Unfortunately, little is known about the LIA glacier changes in remote areas of continental Siberia. In this work we studied the evolution of the glaciers of the Kodar Range, southeast Siberia. These glaciers are mainly of small size (<0.5 km2), cirque and cirque-valley, with predominant northern and north-eastern aspects, located at elevations of 1900–2800 m a.s.l. Using field and satellite imagery data over the 2001–2013 period (Landsat ETM+, Cartosat-1, WorldView-2) we mapped the glaciers, equilibrium line altitudes (ELAs) and the LIA moraines. Modern ELAs vary from 1945 to 2615 m a.s.l. (mean value is 2286 ± 162 m) and demonstrate NNW to SSE increasing regional trend (from 2060 to 2430 m a.s.l.) with local ELA variability due to orography of ±114 m. The extents of the LIA glaciers were reconstructed from terminal moraines, located in front of the glacier termini. These moraines are of fresh morphology, non-vegetated, and locally dated by lichenometry at the mid-18th century. Since the LIA the total glacier area decreased from 19 km2 to 9 km2 (by 53%) and glacier termini retreated, on average, by 440 m. South and south-west facing glaciers shrunk 1.5–2 times stronger than those with northern and north-eastern aspects. Using the toe-to-headwall altitude ratio (THAR) and toe-to-summit altitude method (TSAM), the LIA ELAs were calculated. The LIA ELAs lowered, on average, by 40–60 m, while the ELA changes on south and south-west facing glaciers (mean value of 80–100 m) was 2–2.5 times greater than of the northern. ELA depression during the LIA corresponded to decrease in mean summer temperature of 0.9–1.1 °C (if precipitation was equal to the present). Temperature increase was mainly responsible for ELA rising since the LIA, however, the response of small glaciers could be modulated by other factors (e.g. local insolation or precipitation). Stronger reduction of the south and south-west facing Kodar glaciers can be explained by their greater sensitivity to both solar radiation and snow nourishment with southern cyclones and East Asian monsoon.

Changes in the mountain river discharge in the northern Tien Shan since the mid-20th Century: Results from the analysis of a homogeneous daily streamflow data set from seven catchments

This study is an assessment of the changes in seasonal and monthly flow in seven catchments draining the northern Tien Shan Mountains in Central Asia over a period from the 1950s to the present day. The purpose is to provide a first assessment of the flow response to climate change in regionally important catchments given their contribution to the water resource. All the catchments have a natural flow regime, and are therefore sensitive to climate change, but differ in area, elevation and glacial extent. Trends in flow were characterised using the Mann-Kendall test for standard meteorological seasons and individual months for mean flow, five flow quantiles and peak-over-threshold series for the period 1974–2013 at all sites and from the 1950s where data were available. The results were related to trends in seasonal temperature and precipitation from the regional high-elevation meteorological stations and glacier mass balance, equilibrium line altitude (ELA) and accumulation area ratio (AAR) records from the Tuyuksu glacier. The results show no reduction in streamflow in any catchment or season in the northern Tien Shan since the 1950s. Positive trends in all flow indicators, including peak-over-threshold frequency, were observed in catchments with higher glacierization of over 10% and extensive presence of rock glaciers and permafrost indicating increased melt over the period which is characterised by a long-term increase in temperature. These trends were most evident in autumn and winter. In catchments with low glacierization, variability in summer flow was controlled primarily by precipitation of the preceding cold season. Correlation with glacier mass balance was weak but changes in ELA and AAR indicate that production of liquid runoff at higher elevations contributes to increased streamflow partly compensating for the declining glacier area. The observed changes in streamflow do not suggest any immediate problems with water availability in the northern Tien Shan. On the contrary, increased autumn and winter flows point at a more prolonged recharge of reservoirs and aquifers though eventually this water source will be exhausted.

How sensitive are mountain glaciers to climate change? Insights from a block model

ABSTRACTSimple models of glacier volume evolution are important in understanding features of glacier response to climate change, due to the scarcity of data adequate for running more complex models on a global scale. Two quantities of interest in a glacier's response to climate changes are its response time and its volume sensitivity to changes in the equilibrium line altitude (ELA). We derive a simplified, computationally inexpensive model of glacier volume evolution based on a block model with volume–area–length scaling. After analyzing its steady-state properties, we apply the model to each mountain glacier worldwide and estimate regionally differentiated response times and sensitivities to ELA changes. We use a statistical method from the family of global sensitivity analysis methods to determine the glacier quantities, geometric and climatic, that most influence the model output. The response time is dominated by the climatic setting reflected in the mass-balance gradient in the ablation zone, followed by the surface slope, while volume sensitivity is mainly affected by glacier size, followed by the surface slope.

Sensitivity of glaciation in the arid subtropical Andes to changes in temperature, precipitation, and solar radiation

The subtropical Andes (18.5–27 °S) have been glaciated in the past, but are presently glacier-free. We use idealized model experiments to quantify glacier sensitivity to changes in climate in order to investigate the climatic drivers of past glaciations. We quantify the equilibrium line altitude (ELA) sensitivity (the change in ELA per change in climate) to temperature, precipitation, and shortwave radiation for three distinct climatic regions in the subtropical Andes. We find that in the western cordillera, where conditions are hyper-arid with the highest solar radiation on Earth, ELA sensitivity is as high as 34 m per % increase in precipitation, and 70 m per % decrease in shortwave radiation. This is compared with the eastern cordillera, where precipitation is the highest of the three regions, and ELA sensitivity is only 10 m per % increase in precipitation, and 25 m per % decrease in shortwave radiation. The high ELA sensitivity to shortwave radiation highlights the influence of radiation on mass balance of high elevation and low-latitude glaciers. We also consider these quantified ELA sensitivities in context of previously dated glacial deposits from the regions. Our results suggest that glaciation of the humid eastern cordillera was driven primarily by lower temperatures, while glaciations of the arid Altiplano and western cordillera were also influenced by increases in precipitation and decreases in shortwave radiation. Using paleoclimate records from the timing of glaciation, we find that glaciation of the hyper-arid western cordillera can be explained by precipitation increases of 90–160% (1.9–2.6× higher than modern), in conjunction with associated decreases in shortwave radiation of 7–12% and in temperature of 3.5 °C.

Impacts of Modern Glacier Changes on Surface Water Resources in Western and Northern Mongolia

Water trapped in glaciers and in lakes impounded by landforms created by glaciers (glacial lakes) are an important component of the hydrology and water resources in high mountain areas of Central Asia. Changes in modern glaciers and glacial lakes are an important component of the hydrology of watersheds in the Mongolian Altai and Khuvsgul Mountain Ranges, western and northern Mongolia, respectively. Here we focus on Mt. Ikh Turgen and Mt. Munkh Saridag, isolated mountains of the Mongolian Altai and Khuvsgul Mountain Ranges, respectively. We use remote sensing to track changes in modern glaciers over time with mapping at scales of 1:200,000 for Mt. Ikh Turgen and 1:90,000 for Mt. Munkh Saridag based on imagery from Google Earth, 30 m resolution Aster Digital Elevation Model (DEM) and 30 m resolution Landsat 5 TM. Mt. Ikh Turgen lost 45.6% of its total glacier area between 1970 (41.4 km2) and 2011 (18.9 km2) and the Equilibrium Line Altitude (ELA) of the glaciers increased in elevation by 98 m and 144 m on north and south aspects, respectively. Mt. Munkh Saridag lost 57.3% of its total glacier area between 1970 (901 m2) and 2007 (381 m2) and the local ELA rose by 47 m and 80 m on north and south aspects, respectively. These mountains are located at similar latitudes, and so the greater percentage loss of glacier area in Mt. Munkh Saridag and faster changes in ELAs in Mt. Ikh Turgen may reflect variations in elevation and aspect, duration of solar radiation, and vulnerability to solar radiation, as well as variations in glacier scale. This study demonstrates the importance of spatial analyses of modern glaciers in understanding the context of hydrological changes within which any sustainable water resource management plan must be situated.

Changes in equilibrium line altitude of glacier systems in Northeastern Siberia for the late 20th–early 21st centuries.

Changes in equilibrium line altitude of glacier systems in Northeastern Siberia for the late 20th–early 21st centuries.

Изменения высоты границы питания ледниковых систем на северо-востоке Сибири в конце XX–начале XXI века

Изменения высоты границы питания ледниковых систем на северо-востоке Сибири в конце XX–начале XXI века

Temporal fluctuations and frontal area change of Bangni and Dunagiri glaciers from 1962 to 2013, Dhauliganga Basin, central Himalaya, India

Glaciers have been receding for the last 100years in many glaciated regions of the world, and the rate of recession has accelerated during the last 60years. Recent assessments of changes in glaciers in the Himalaya have usually recognized their variable rate of recession. The present study deals with snout retreat, frontal area vacation, and estimation of the equilibrium line altitude (ELA) of Bangni and Dunagiri glaciers, in the Dhauliganga Basin, central Himalaya (India), using multi-image satellite data (Landsat MSS, 1976; Landsat TM, 1990; Landsat ETM+, 2005) and Survey of India topographic maps (1962; 1:50,000) along with field surveys (2012 to 2014) for the period of 1962–2013. The meteorological data of the India Meteorological Department (IMD) and TRMM suggested that the central Himalaya received less precipitation between 1960 and 1990. Because of the less precipitation, glaciers receded rapidly during this period. The present study shows that Bangni and Dunagiri glaciers retreated ~2080±162m and ~484±38m with average rates of ~41±3.2ma−1 and ~9±0.6ma−1 between 1962 and 2013, respectively. During this period Bangni and Dunagiri glaciers lost about 17% and 11% of their length, respectively. The result also suggested that Bangni Glacier vacated ~598,948±12,257m2 frontal area, while Dunagiri Glacier vacated ~170,428±7833m2 frontal area between 1962 and 2013. Moreover, the estimated ELA change for Bangni Glacier was ~64±30m upward during the study period. The Geological Survey of India (GSI, 1998a,b) suggested that the ELA of Dunagiri Glacier rose ~28m between 1984 and 1992 and that the glacier lost ~(−)16×106m3w.e. ice with an average rate of loss of ~(−)1.04mw.e.a−1. The geomorphology of the Dunagiri Valley reflected that Bangni and Dunagiri glaciers were joined together in the past. Nevertheless, these two glaciers retreat at different rates, indicating that climate change is not the only factor in glacier retreat but that geometry (size, shape, slope, and orientation) of the glacier and basin topography also plays a major role.