Reduction In Glacier Area Research Articles

Remote sensing monitoring of glacier area and volume changes in glacier-fed mountainous watershed on the Northern margin of the Qinghai-Tibet Plateau under climate change.

Steady glacier runoff is related to the security and resilience of water resources in meltwater recharge basins, so the status and change of glaciers and their response to climate change in the upper reaches have received widespread concerns. Here, the spatiotemporal characteristics of glacier wastage in the Upper Reaches of Shule River Basin (URSRB) driven by climate change were analyzed based on multi-source and multi-temporal remotely sensed images. Firstly, we extracted multi-temporal glacier outlines from the Landsat time series data using Google Earth Engine (GEE) for seven different periods every approximately 5years from 1990 to 2020. The spatiotemporal analysis of URSRB glaciers demonstrates a sustained reduction in glacier area from 481.07 ± 24.24 km2 in 1990 to 384.05 ± 22.71 km2 in 2020, corresponding to a glacier shrinkage rate of - 0.67 ± 0.23%/year, characterized by considerable temporal variability. Secondly, multi-temporal DEMs derived from ASTER stereo imagery spanning from 2000 to 2020 were used to compute the glacier surface elevation changes and determine the glacier mass loss. The overall glacier surface elevation change rate was - 0.32 ± 0.14m/year, equivalent to a mass balance of - 0.28 ± 0.12m w.e./year. Lastly, to better apprehend the long-term response of URSRB glaciers to climate change, studies on climate change were carried out based on the EAR5-Land reanalysis dataset. The long-term trend of glacier wastage is attributed to the increase in summer temperature, and the negative effects of increased summer temperature on glaciers exceeded the positive effects of increased annual precipitation. In summary, glaciers in the URSRB have experienced a significant area reduction and accelerated mass loss against the backdrop of climatic warming and humidification.

Climatic factors affecting Kamchatka glacier recession

AbstractThe reduction in the area and volume of glaciation in all mountain regions of the Earth has strongly accelerated for the last decades. In this work, we analysed the trends of the main climatic parameters which caused the glacier recession in the Kamchatka Peninsula. It was shown that the glaciers of the northern part of the Sredinny Range decreased by 125 km2 (35.6%) from 1950 to 2016–2017. The average rate of their reduction in the period from 2002 to 2016–2017 (1.45%/year) increased approximately 4.3 times compared to the period 1950–2002 (0.34%/year). The greatest reduction is observed in small glaciers with an area of less than 0.1 km2 and in glaciers with southeastern and southern expositions. On the Kronotsky Peninsula, the glacier area reduction for 1957–2019 was equal to 32.1 km2 (35.6%), and the rates were almost the same in the periods of 1957–2000 (0.61%/year) and 2000–2019 (0.67%/year). According to the data of weather stations and ERA5 reanalysis, it was shown that, in the ablation (summer) period the warming rate was minimal (0.3°C/10 years) and in the accumulation period a significant decrease in precipitation (5%–10%/10 years) was revealed in some areas. At the same time, a significant increase in the radiation balance was revealed in the warm season along with a tendency in downward shortwave radiation increase for the last two decades due to a decrease in cloud amount. These trends are in good agreement with the growth of the geopotential height over the North Pacific during the warm season in the 21st century, and with the growth of velocity divergence in the middle troposphere and the intensification of downward air movements. All this confirms an increase in anticyclone frequency in the warm season, which could be the cause of a radiation balance increase and, consequently, an increase in glacier ablation.

Climatic and topographic controls on glacial changes (1973-2020) in Shigar Basin, Central Karakoram, Northern Pakistan.

The Hindukush, Karakorum, and Himalaya (HKH) mountains are often referred to as the "Third Pole" because of high snow, being a major freshwater resource and early indicator of climate change. Therefore, research on the dynamics of glacier changes and their relationship with climate and topographic variability is essential for sustainable water resource management and adaptation strategies in Pakistan. In this contribution, we delineated 187 glaciers and examined these glacier changes in the Shigar Basin from 1973 to 2020 using Corona, Landsat Operational Land Imager/Enhanced Thematic Mapper Plus/Thematic Mapper/Multispectral Scanner System (OLI/ETM/TM/MSS), Alaska Satellite Facility (ASF), and Shuttle Radar Topography Mission Digital Elevation Model (SRTM DEM) imageries. The total glacier area decreased from 2796.31 ± 132 km2 in 1973 to 2756.27 ± 63 km2 in 2020 at an average rate of - 0.83 ± 0.03 km2yr-1. Specifically, during the period of 1990-2000, these glaciers shrank most heavily at an average rate of - 2.372 ± 0.08 km2yr-1. In contrast, an increased rate of 0.57 ± 0.02 km2yr-1 in total glacier area was observed during the recent decade (2010-2020). Moreover, the glaciers with gentle slopes retreated less heavily than the steep ones. There was reduction in glacier coverage and length for all slope classes, and a small reduction was observed with gentle slopes, while higher losses were observed on steep slope gradients. The transition of glaciers in the Shigar Basin may be attributed by the direct influence of glacier size and topographical characteristics. By comparing with climate records, our findings suggest that the overall reduction in glacier area from 1973 to 2020 was associated with declining precipitation (- 0.78 mmm/year) and rising temperature (0.045°C/year) trends in the region, and glacier advances in recent decade (2010-2020) were likely to be driven by increased winter and autumn precipitation.

Glacier area changes in Novaya Zemlya from 1986–89 to 2019–21 using object-based image analysis in Google Earth Engine

AbstractClimate change has had a significant impact on glacier recession, particularly in the Arctic, where glacier meltwater is an important contributor to global sea-level rise. Therefore, it is important to accurately quantify glacier recession within this sensitive region, using multiple observations of glacier extent. In this study, we mapped 480 glaciers in Novaya Zemlya, Russian Arctic, using object-based image analysis applied to multispectral Landsat satellite imagery in Google Earth Engine and quantify the area changes between 1986–89 and 2019–21. The results show that in 1986–89, the total glacierized area was 22 990 ± 301 km2, in 2000–01 the area was 22 525 ± 308 km2 and by 2019–21 the glacier area reduced to 21 670 ± 292 km2, representing a total of 5.8% reduction in glacier area between 1986–89 and 2019–21. Higher glacier area loss was observed on the Barents Sea coast (7.3%) compared to the Kara (4.2%), reflecting previously observed differences in warming trends. The accuracy of the automatically generated outlines of each layer (1986–89, 2000–01 and 2019–21) was evaluated by comparing with manually corrected outlines (reference data) using random sampling, resulting in an overall accuracy estimate of between 96 and 97% compared to the reference data. This automated approach in Google Earth Engine is a promising tool for rapidly mapping glacier change that reduces the amount of time required to generate accurate glacier outlines.

Topographic controls on ice flow and recession for Juneau Icefield (Alaska/British Columbia)

AbstractGlobally, mountain glaciers and ice caps are losing dramatic volumes of ice. The resultant sea‐level rise is dominated by contributions from Alaska. Plateau icefields may be especially sensitive to climate change due to the non‐linear controls their topography imparts on their response to climate change. However, Alaskan plateau icefields have been subject to little structural glaciological or regional geomorphological assessment, which makes the controls on their present and former mass balance difficult to ascertain.We inventoried 1050 glaciers and 368 lakes in the Juneau Icefield region for the year 2019. We found that 63 glaciers had disappeared since the 2005 inventory, with a reduction in glacier area of 422 km2 (10.0%). We also present the first structural glaciological and geomorphological map for an entire icefield in Alaska. Glaciological mapping of >20 800 features included crevasses, debris cover, foliation, ogives, medial moraines and, importantly, areas of glacier fragmentation, where glaciers either separated from tributaries via lateral recession (n = 59), or disconnected within areas of former icefalls (n = 281). Geomorphological mapping of >10 200 landforms included glacial moraines, glacial lakes, trimlines, flutes and cirques. These landforms were generated by a temperate icefield during the Little Ice Age (LIA) neoglaciation. These data demonstrate that the present‐day outlet glaciers, which have a similar thermal and ice‐flow regime, have undergone largely continuous recession since the LIA. Importantly, disconnections occurring within glaciers can separate accumulation and ablation zones, increasing rates of glacier mass loss. We show that glacier disconnections are widespread across the icefield and should be critically taken into consideration when icefield vulnerability to climate change is considered.

Cambio de área glaciar en el volcán Maipo (Andes Centrales), una aproximación morfométrica: 4 décadas de registros satelitales

Current climatic conditions in Central Andes (CA) (31-36 °S) have triggered the reduction of glacier area. Although CA are geographically circumscribed to an area under the same macroclimatic domain, their rugged topography creates several topoclimates as response to the effects of elevation, slope and aspect (morphometric factors). This study explores the impact of morphometric factors on the evolution of the glacial surface located above of Maipo volcano (34°09'50''S; 69°49'53''W). Through the use of 11 LANDSAT images (MSS, TM and OLI), the spatio-temporal evolution (period 1976-2020) of the glacier area was reconstructed. On this period, glacier area was reduced by 6 ± 0.5 km2 (-0.14 ± 0.01 km2a-1), equal to 63 % of 1976 glacial area (9.6 ± 0.5 km2). Fifty percent of the reduction occurred between 3,900 and 4,000 m elevation, with absolute losses towards lower elevations. In addition, it was detected that for every 100 m of ascent the relative area loss rate decreased 0.1 %a-1 (R2 = 0.81; p-value

Monitoring Changes to Arctic Vegetation and Glaciers at Ny-Ålesund, Svalbard, Based on Time Series Remote Sensing

Climate change has profoundly affected global ecological security. The most vulnerable region on Earth is the high-latitude Arctic. Identifying the changes in vegetation coverage and glaciers in high-latitude Arctic coastal regions is important for understanding the process and impact of global climate change. Ny-Ålesund, the northern-most human settlement, is typical of these coastal regions and was used as a study site. Vegetation and glacier changes over the past 35 years were studied using time series remote sensing data from Landsat 5/7/8 acquired in 1985, 1989, 2000, 2011, 2015 and 2019. Site survey data in 2019, a digital elevation model from 2009 and meteorological data observed from 1985 to 2019 were also used. The vegetation in the Ny-Ålesund coastal zone showed a trend of declining and then increasing, with a breaking point in 2000. However, the area of vegetation with coverage greater than 30% increased over the whole study period, and the wetland moss area also increased, which may be caused by the accelerated melting of glaciers. Human activities were responsible for the decline in vegetation cover around Ny-Ålesund owing to the construction of the town and airport. Even in areas with vegetation coverage of only 13%, there were at least five species of high-latitude plants. The melting rate of five major glaciers in the study area accelerated, and approximately 82% of the reduction in glacier area occurred after 2000. The elevation of the lowest boundary of the five glaciers increased by 50–70 m. The increase in precipitation and the average annual temperature after 2000 explains the changes in both vegetation coverage and glaciers in the study period.

Assessment of glacier status and its controlling parameters from 1990 to 2018 of Hunza Basin, Western Karakorum.

Ice masses and snow of Hunza River Basin (HRB) are an important primary source of fresh water and lifeline for downstream inhabitants. Changing climatic conditions seriously put an impact on these available ice and snow masses. These glaciers may affect downstream population by glacial lake outburst floods (GLOF) and surge events due to climatic variation. So, monitoring of these glaciers and available ice masses is important. This research delivers an approach for dynamics of major glaciers of the Hunza River Basin. We delineated 27 major glaciers of HRB and examined their status by using Landsat (OLI, ETM+, ETM, TM), digital elevation model (DEM) over the period of 1990-2018. In 1990, the total area covered by these glaciers is about 2589.75 ± 86 km2 and about 2565.12 ± 68km2 in 2018. Our results revealed that from 2009 to 2015, glacier coverage of HRB advanced with a mean annual advance rate of 2.22 ± 0.1 km2 a-1. Conversely, from 1994 to 1999, the strongest reduction in glacier area with a mean rate of - 3.126 ± 0.3 km2 a-1 is recorded. The glaciers of HRB are relatively stable compared to Hindukush, Himalayan, and Tibetan Plateau region of the world. The steep slope glacier's retreat rate is more than that of gentle slope glaciers, and the glaciers below an elevation of 5000 m above sea level change significantly. Based on climate data from 1995 to 2018, HRB shows a decreasing trend in temperature and increasing precipitation. The glacier area's overall retreat is due to an increase in summer temperature while the glacier advancement is induced possibly by winter and autumn precipitation.

Sensitivities of Hydrological Processes to Climate Changes in a Central Asian Glacierized Basin

This study used the WASA (Water Availability in Semi-Arid Environments) hydrological model to simulate runoff generation processes and glacier evolution in the Ala-Archa basin in Central Asia. Model parameters were calibrated by observations of streamflow, satellite snow cover area (SCA) and annual glacier mass balance (GMB). Temperature and precipitation change scenarios were set up by perturbations of the reference measurements in a 20-year period of 1997 to 2016. Seven temperature warming scenarios with an increment of +1°C and six precipitation change scenarios ranging from 70 to 130% of the reference precipitation were used to investigate the sensitivities of hydrological processes to climate changes in the study basin. Results indicate that: (1) Annual runoff increased with rising temperature (T) and precipitation (P) at rates of 76 mm/+1°C and 62 mm/+10%P, respectively. Glacier area was more sensitive to T changes than to P changes. The total glacier area in the basin decreased with T warming at a rate of −0.47 km2/+1°C, whilst increasing with rising P at a rate of 0.16 km2/+10%P. (2) The basin runoff switched from rainfall and groundwater-dominated to ice melt-dominated with warming T, while the dominance of rainfall and groundwater were strongly enhanced by rising P. Proportion of rainfall in the total water input for runoff generation decreased with T warming at a rate of −0.5%/+1°C, while increasing with P increases at a rate of 1.2%/+10% P. Ice melt proportion changed with T and P increases at rates of 4.2%/+1°C and −1.8%/+10%P, respectively. Groundwater contribution to total runoff decreased by −2.8% per T warming of 1°C, but increased by 1.5% per P increase of 10%. (3) The maximum P changes (±30%) could only compensate the effects of T warming of 0.5 to 2.5°C. Increase of annual runoff forced by T warming lower than 2.2°C could be compensated by decrease caused by the maximum P decrease of −30%. Decrease of glacier area caused by 1°C warming cannot be compensated by the maximum P increase of +30%. The combined input of 20% increase of P and T warming of 6°C resulted in 90% increase of annual runoff, and 8% reduction of glacier area. The results inform understandings of the hydrological responses to potential climate changes in glacierized basins in Central Asia.

Very Small Glaciers as Geoheritage: Combining a Spatio-Temporal Visualisation of Their Development and Related Effects of Climate Change

Outside the main mountain ranges and high North and South regions, individual isolated very small glaciers are the only glacier remnants and exceptional high-mountain active geomorphosites, which can be used to represent climate change consequences first hand to the local general public. The isolated, very small Triglav glacier in Slovenia was used to represent 3D glacier area changes for the period 1829–2016, together with long-term meteorological changes. Spatio-temporal changes of the glacier were derived mainly from old images and postcards with the help of interactive orientation (monoplotting), which enables the acquisition of a 3D glacier boundary from a single image by using a modern detailed digital elevation model. Very intuitive 3D visualisation was prepared, which shows the spatio-temporal changes of the glacier area, together with changes in average annual temperature and maximum annual snow depth. The last two are presented by colour palettes, where red colours represent stages when temperatures or maximum snow depths deviate from long-term averages in a negative way, meaning accelerating the glacier area reduction. Blue colours are used for stages when these parameters deviate from long-term averages in a positive way, meaning preserving the glacier area. From this 3D visualisation, one can easily recognise which meteorological parameter is the most important for the Triglav glacier preservation; this is the maximum annual snow depth. Such kind of 3D visualisation has a great potential for promotion of other active or evolving passive geomorphosites too.

Glacier retreat in the High Arctic: opportunity or threat for ectomycorrhizal diversity?

Climate change causes Arctic glaciers to retreat faster, exposing new areas for colonization. Several pioneer plants likely to colonize recent deglaciated, nutrient-poor areas depend on fungal partners for successful establishment. Little is known about general patterns or characteristics of facilitating fungal pioneers and how they vary with regional climate in the Arctic. The High Arctic Archipelago Svalbard represents an excellent study system to address these questions, as glaciers cover ∼60% of the land surface and recent estimations suggest at least 7% reduction of glacier area since 1960s.Rootsof two ectomycorrhizal (ECM) plants (Salix polaris and Bistorta vivipara) were sampled in eight glacier forelands. Associated ECM fungi were assessed using DNA metabarcoding. About 25% of the diversity was unknown at family level, indicating presence of undescribed species. Seven genera dominated based on richness and abundance, but their relative importance varied with local factors. The genus Geopora showed surprisingly high richness and abundance, particularly in dry, nutrient-poor forelands. Such forelands will diminish along with increasing temperature and precipitation, and faster succession. Our results support a taxonomical shift in pioneer ECM diversity with climate change, and we are likely to lose unknown fungal diversity, without knowing their identity or ecological importance.

Recent Changes in Water Discharge in Snow and Glacier Melt-Dominated Rivers in the Tienshan Mountains, Central Asia

Global warming has generally led to changes in river runoffs fed by snow and glacier meltwater in mountain ranges. The runoff of the Aksu River, which originates in the Southern Tienshan Mountains, exhibited a positive trend during 1979–2002, but this trend reversed during 2002–2015. Through a comprehensive analysis, this study aims to estimate potential reasons for changes in the runoff of its two contrasting headwaters: the Toxkan and Kumalak Rivers, based on climatic data, the altitude of the 0 °C isotherm, glacier mass balance (GMB), snow cover area (SCA), snow depth (SD) and the sensitivity model. For the Toxkan River, the decrease in spring runoff mainly resulted from reductions in precipitation, whereas the decrease in summer runoff was mainly caused by early snowmelt in spring and a much-reduced snow meltwater supply in summer. In addition, the obvious glacier area reduction in the catchment (decreased to less than 4%) also contributed to the reduced summer runoff. For the Kumalak River, a sharp decrease rate of 10.21 × 108 m3/decade in runoff was detected due to summertime cooling of both surface and upper air temperatures. Reduced summer temperatures with a positive trend in precipitation not only inhibited glacier melting but also dropped the 0 °C layer altitude, resulting in a significant increase in summertime SCA and SD, a slowing of the glacier negative mass balance, and a lowering of the snow-line altitude.

LO STATO ATTUALE DEI GHIACCIAI ITALIANI E LA LORO RECENTE EVOLUZIONE

Mountain glaciers represent an important hydrological and touristic resource, and their recent evolution provides a dramatic evidence of climate change for the general public. Glacier inventories, quantifying glacier characteristics and evolution, are an important tool to describe and manage high mountain glacier environments and Italy has developed a long tradition in this sector. Our country was the first to provide itself with a glacier inventory, compiled by Comitato Glaciologico Italiano and CNR, showing a glacier surface of 530 km2. A recent project, coordinated by Università Statale di Milano with the support of private bodies and the cooperation of Comitato EvK2CNR and Comitato Glaciologico Italiano, led to the development of the new Italian Glacier Inventory, a national atlas produced from the analysis of color orthophotos at high resolution acquired between 2005 and 2011. The New Italian Glacier Inventory lists 903 glaciers, covering an area of 370 km2. The largest part of glacier area is located in Val d’Aosta (36.15% of the total), followed by Lombardia and South Tyrol. 84% of glaciers (considering the number of glaciers) have an area lower than 0.5 km2 and jointly account for 21% of the total glacier surface. Glaciers larger than 1 Km2 make up 9.4% of the total number, but cover 67.8% of the total glacier area. The comparison between data from the New Italian Glacier Inventory and the CGI-CNR inventory (1959-1962) shows a 30% reduction in glacier area in Italy; considering instead the World Glacier Inventory or WGI, published at the end of the ‘80s, which reported 1381 glaciers and an area of 609 km2, glacier loss sums up to 478 glaciers and an area of 239 km2 (-39%). This shrinkage has led to rapid and significant changes to high mountain landscapes, notably glacier fragmentation, an increase in deglaciated areas, the formation of proglacial lakes and the development of pioneer vegetation.

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.

Spatial Variability in Patterns of Glacier Change across the Manaslu Range, Central Himalaya

This study assesses changes in glacier area, velocity and geodetic mass balance for the glaciers in the Manaslu region of Nepal, a previously undocumented region of the Himalayas. We studied changes between 1970 (for select glaciers), 2000, 2005 and 2013 using freely available Landsat satellite imagery, the SRTM Digital Elevation Model (DEM) and a DEM based on Worldview imagery. Our results show a complex pattern of mass changes across the region, with glaciers lowering on average by -0.25 ± 0.08 m a-1 between 2000 and 2013 which equates to a negative geodetic mass balance of -0.21 ± 0.16 m w.e.a-1. Over approximately the same time period (1999 to 2013) the glaciers underwent a -16.0% decrease in mean surface velocity over their debris-covered tongues as well as a reduction in glacier area of -8.2%. The rates of glacier change appear to vary between the different time periods, with glacier losses increasing in most cases. The glaciers on Manaslu itself underwent a change in surface elevation of -0.46 ± 0.03 m a-1 between 1970 and 2000 and -0.99 ± 0.08 m a-1 between 2000 and 2013. Rates of glacier area shrinkage for the same glaciers increased from -0.36 km2 a-1 between 1970 and 2001 to -2.28 km2 a-1 between 2005 and 2013. Glacier change varies across the region and seems to relate to a combination of glacier hypsometry, glacier elevation range and the presence and distribution of supraglacial debris. Lower-elevation, debris-free glaciers with bottom-heavy hypsometries are losing most mass. As the glaciers in the Manaslu region continue to stagnate, an accumulation and thickening of the debris-cover is likely, thereby insulating the glacier and further complicating future glacier responses to climate.

The role of glacier changes and threshold definition in the characterisation of future streamflow droughts in glacierised catchments

Abstract. Glaciers are essential hydrological reservoirs, storing and releasing water at various timescales. Short-term variability in glacier melt is one of the causes of streamflow droughts, here defined as deficiencies from the flow regime. Streamflow droughts in glacierised catchments have a wide range of interlinked causing factors related to precipitation and temperature on short and long timescales. Climate change affects glacier storage capacity, with resulting consequences for discharge regimes and streamflow drought. Future projections of streamflow drought in glacierised basins can, however, strongly depend on the modelling strategies and analysis approaches applied. Here, we examine the effect of different approaches, concerning the glacier modelling and the drought threshold, on the characterisation of streamflow droughts in glacierised catchments. Streamflow is simulated with the Hydrologiska Byråns Vattenbalansavdelning (HBV-light) model for two case study catchments, the Nigardsbreen catchment in Norway and the Wolverine catchment in Alaska, and two future climate change scenarios (RCP4.5 and RCP8.5). Two types of glacier modelling are applied, a constant and dynamic glacier area conceptualisation. Streamflow droughts are identified with the variable threshold level method and their characteristics are compared between two periods, a historical (1975–2004) and future (2071–2100) period. Two existing threshold approaches to define future droughts are employed: (1) the threshold from the historical period; (2) a transient threshold approach, whereby the threshold adapts every year in the future to the changing regimes. Results show that drought characteristics differ among the combinations of glacier area modelling and thresholds. The historical threshold combined with a dynamic glacier area projects extreme increases in drought severity in the future, caused by the regime shift due to a reduction in glacier area. The historical threshold combined with a constant glacier area results in a drastic decrease of the number of droughts. The drought characteristics between future and historical periods are more similar when the transient threshold is used, for both glacier area conceptualisations. With the transient threshold, factors causing future droughts can be analysed. This study revealed the different effects of methodological choices on future streamflow drought projections and it highlights how the options can be used to analyse different aspects of future droughts: the transient threshold for analysing future drought processes, the historical threshold to assess changes between periods, the constant glacier area to analyse the effect of short-term climate variability on droughts and the dynamic glacier area to model more realistic future discharges under climate change.

Variations of Laohugou Glacier No. 12 in the western Qilian Mountains, China, from 1957 to 2015

Glaciers were solid reservoirs and important water resources in western China, but they were retreating significantly in context of global warming. Laohugou Glacier No. 12 was the largest valley glacier in Qilian Mountains. In this study, real-time kinematic (RTK) data, topographic map and WorldView-2 satellite imagery were used to measure changes in terminus, extent and volume of Laohugou Glacier No. 12. Results showed that Laohugou Glacier No. 12 was shrinking significantly since 1957. From 1960 to 2015, the terminus reduction of Laohugou Glacier No. 12 was 402.96 m (3.99%) in total, and glacier length decreased to 9.7 km from 10.1 km. Reduction of glacier area and volume were the most obvious. From 1957 to 2015, glacier area and volume decreased by 1.54 km2 (7.03%) and 0.1816 km3, respectively. Reduction trend of terminus and area was slowing in 1950 - 1980s, even stable for a period in the mid-1980s, and then accelerated. Ice core analysis result and nearly meteorological station data shown an increasing trend of temperature in 1957 - 2015, it was a main reason of continuous retreating of Laohugou Glacier No.12.

Decadal Change in Glacier Area in the Chorabari Sub Watershed

This area looks at glacier area change in Chorabari Sub Watershed for 1962-1990 and 2000-2016 periods. Study area of Chorabari Sub Watershed extends between the latitudes of 28o-31oN to longitudes 77o-81°E. Chorabari Sub Watershed is the part of Mandakini basin and it has total number of 40 glaciers covered an area of 81.64 km 2 with the ice reserve of 5.9856 km 2 . The reduction in the glacier area has been observed on the lateral side of Chorabari glacier and not on the snout position. Overall reduction in the basin glacier area was observed 1.23 km 2 during the year 1990 to 2016. In addition, this paper describes a method for estimating the ice surface elevation changes using the SRTM (2000) and elevation data generated from topographic maps (1962) to quantify the ice thickness change for the 1962-2000 periods.

Streamflow response to the rapid retreat of a lake‐calving glacier

AbstractThere has been increasing attention over the last decade to the potential effects of glacier retreat on downstream discharge and aquatic habitat. This study focused on streamflow variability downstream of Bridge Glacier in the southern Coast Mountains of BC between 1979 and 2014, prior to and during a period in which the glacier experienced enhanced calving and rapid retreat across a lake‐filled basin. Here we combined empirical trend detection and a conceptual‐parametric hydrological model to address the following hypotheses: (1) streamflow trends in late summer and early autumn should reflect the opposing influences of climatic warming (which would tend to increase unit‐area meltwater production) and the reduction in glacier area (which would tend to reduce the total volume of meltwater generated), and (2) winter streamflow should increase because of displacement of lake water as ice flows past the grounding line and calves into the lake basin. In relation to the first hypothesis, we found no significant trends in monthly discharge during summer. However, applying regression analysis to account for air temperature and precipitation variations, weak but statistically significant negative trends were detected for August and melt season discharge. The HBV‐EC model was applied using time‐varying glacier cover, as derived from Landsat imagery. Relative to simulations based on constant glacier extent, model results indicated that glacier recession caused a decline in mean monthly streamflow of 9% in August and 11% in September. These declines in late‐summer streamflow are consistent with the results from our empirical analysis. The second hypothesis is supported by the finding of positive trends for December, January, and February discharge. Despite the modelled declines in late‐summer mean monthly streamflow, recorded discharge data exhibited neither positive nor negative trends during the melt season, suggesting that Bridge Glacier may currently be at or close to the point of peak water. Further analysis of the impact of lake‐terminating glaciers on downstream discharge is needed to refine the peak water model. Copyright © 2016 John Wiley & Sons, Ltd.

Decadal Scale Changes in Glacier Area in the Hohe Tauern National Park (Austria) Determined by Object-Based Image Analysis

In this paper, we semi-automatically classify clean and debris-covered ice for 145 glaciers within Hohe Tauern National Park in the Austrian Alps for the years 1985, 2003, and 2013. We also map the end-summer transient snowline (TSL), which approximates the annual Equilibrium Line Altitude (ELA). By comparing our results with the Austrian Glacier Inventories from 1969 and 1998, we calculate a mean reduction in glacier area of 33% between 1969 and 2013. The total ice area reduced at a mean rate of 1.4 km2 per year. This TSL rose by 92 m between 1985 and 2013 to an altitude of 3005 m. Despite some limitations, such as some seasonal snow being present at higher elevations, as well as uncertainties related to the range of years that the LiDAR DEM was collected, our results show that the glaciers within Hohe Tauern National Park conform to the heavy shrinkage experienced in other areas of the European Alps. Moreover, we believe that Object-Based Image Analysis (OBIA) is a promising methodology for future glacier mapping.