Search

The basic physics of how global warming contributes to sea-level rise has long been understood, but new research gives us a clearer picture of what to expect. Prior to the 1990s, most sea-level rise was attributed to melting glaciers and the thermal expansion of warming ocean waters. However, ice sheets such as those covering Greenland and Antarctica have also begun to melt and play a significant role in raising ocean levels. The author reviews the results of a number of recent studies. Two of them conclude that the seas could rise by 3 or more feet by the year 2100, and one argued that 5 feet or more by 2100 is a possibility. Exactly what happens, and when, will be influenced by the degree to which humans reduce carbon emissions, and the uncertain dynamics of the Antarctic ice sheet. Considerable sea-level rise will occur as a consequence of the global warming humans have already caused. [ABSTRACT FROM AUTHOR]

The article focuses on a study on rise in global temperature increasing greenhouse gas emissions along with loss of rates of glacier mass and mentions water insecurity caused by the disappearance of glaciers. Topics discussed include glacier measurements made on surface and aircraft using aerial photography, lack of records for understanding effects of climate change, and issues of the greenhouse gas emission.

The high tropical Andes are rapidly changing due to climate change, leading to strong biotic community, ecosystem, and landscape transformations. While a wealth of glacier, water resource, and ecosystem-related research exists, an integrated perspective on the drivers and processes of glacier, landscape, and biota dynamics is currently missing. Here, we address this gap by presenting an interdisciplinary review that analyzes past, current, and potential future evidence on climate and glacier driven changes in landscape, ecosystem and biota at different spatial scales. We first review documented glacier changes and landscape evolution over past decades to millennia and analyze projected future glacier shrinkage until 2100 for two case studies in the tropical Andes. The effects of climate and glacier change on high Andean biota are then examined from paleoecological research and comparative gradient analyses to chronosequence and diachronic studies of vegetation dynamics. Our analysis indicates major twenty-first century landscape transformations with important socioecological implications which can be grouped into (i) formation of new lakes and drying of existing lakes as glaciers recede, (ii) alteration of hydrological dynamics in glacier-fed streams and high Andean wetlands, resulting in community composition changes, (iii) upward shifts of species and formation of new communities in deglaciated forefronts,(iv) potential loss of wetland ecosystems, and (v) eventual loss of alpine biota. We advocate strengthening an interdisciplinary research agenda with a strong policy formulation link that enables enhanced cross-sectorial cooperation and knowledge sharing, capacity building of relevant stakeholders, and a more active participation of both government agencies and social organizations. [ABSTRACT FROM AUTHOR]

Climate variability can complicate efforts to interpret any long-term glacier mass-balance trends due to anthropogenic warming. Here we examine the impact of climate variability on the seasonal mass-balance records of 14 glaciers throughout Norway, Sweden and Svalbard using dynamical adjustment, a statistical method that removes orthogonal patterns of variability shared between each mass-balance record and sea-level pressure or sea-surface temperature predictor fields. For each glacier, the two leading predictor patterns explain 27–81% of the winter mass-balance variability and 24–69% of the summer mass-balance variability. The spatial and temporal structure of these patterns indicates that accumulation variability for all of the glaciers is strongly related to the North Atlantic Oscillation (NAO), with the Atlantic Multidecadal Oscillation (AMO) also modulating accumulation variability for the northernmost glaciers. Given this result, predicting glacier change in the region may depend on NAO and AMO predictability. In the raw mass-balance records, the glaciers throughout southern Norway have significantly negative summer trends, whereas the glaciers located closer to the Arctic have negative winter trends. Removing the effects of climate variability suggests it can bias trends in mass-balance records that span a few decades, but its effects on most of the longer-term mass-balance trends are minimal. [ABSTRACT FROM AUTHOR]

Affected by global climate change，most glaciers in southeastern Tibet have deteriorated more and more frequently. The risk of mountain disasters» such as floods, surges and debris flows， has increased sharply in recent years. This paper implements a research on glacial lakes classification by using multi-source synthetic aperture radar (SAR) images. According to the statistical analysis of intensity difference between signals coming from water and non-water objects，a method of glacial lake extraction and dynamic monitoring based on the intensity standardization ratio of sequential SAR images is proposed. Within a typical experimental area in Gongba Glacier basin，the image series of ALOS/PALSAR-1 of Japan Space Agency and Sentinel-1 A of European Space Agency are selected to carry out dynamic extraction of glacial lakes and long-term change analysis over 11 years9 time, just for validation purpose. The temporal and spatial variations of glacial lakes at the end of Gongba Glacier from 2007 to 2018 are successfully obtained. And the further analysis finds out that the volume of glacial lakes increase rapidly in the past ten years. This evidence can also confirm the current situation of aggravated melting of Gongba Glacier. In addition, the recent monitoring results in 2018 show that the expansion of local burst gushes has broken the inherent life cycle of glacial lakes，and even trigger secondary disasters of floods and debris flows. It is necessary to strengthen monitoring and prevention. [ABSTRACT FROM AUTHOR]

Mountain glaciers currently exist in 18 mountainous regions of the continental part of Russia. They occupy a total area of about 3480 km2. Almost all the glaciers in these mountainous areas have receded over the past few decades. The process of glacier retreat leads to landscape change in the glacier zone and can also lead to increased risks of hazards and natural disasters. The existing research on the current state of glaciers and their changes helps us to understand the mechanisms of the changes and to improve forecasts and adaptation strategies. This article presents a review of mountain glacier change estimates in continental Russia over the twentieth and twenty-first centuries. The sources for the estimates include satellite imagery, topographic maps, field research results, and scientific publications. The results of our analysis demonstrate that changes in the main climatic factors, i.e., air temperature and precipitation, determine the general trend in glacier changes in Russia's mountainous regions. Glacier reductions for the second part of twentieth century range from 10.6% (Kamchatka) to 69% (the Koryak Highlands). The differences in the rate and the direction of glacier changes depend on local orographic and climatic features. [ABSTRACT FROM AUTHOR]

Across High Asia, the amount, timing, and spatial patterns of snow and ice melt play key roles in providing water for downstream irrigation, hydropower generation, and general consumption. The goal of this paper is to distinguish the specific contribution of seasonal snow versus glacier ice melt in the major basins of High Mountain Asia: Ganges, Brahmaputra, Indus, Amu Darya, and Syr Darya. Our methodology involves the application of MODIS-derived remote sensing products to separately calculate daily melt outputs from snow and glacier ice. Using an automated partitioning method, we generate daily maps of (1) snow over glacier ice, (2) exposed glacier ice, and (3) snow over land. These are inputs to a temperature index model that yields melt water volumes contributing to river flow. Results for the five major High Mountain Asia basins show that the western regions are heavily reliant on snow and ice melt sources for summer dry season flow when demand is at a peak, whereas monsoon rainfall dominates runoff during the summer period in the east. While uncertainty remains in the temperature index model applied here, our approach to partitioning melt from seasonal snow and glacier ice is both innovative and systematic and more constrained than previous efforts with similar goals. [ABSTRACT FROM AUTHOR]

Glacial retreat reveals the unsettling effects of anthropogenic climate change, and challenges deeply seated cultural ideas about static landscapes. Glaciers have thus emerged as key signifiers of environmental loss. Because they are the outcomes of Westernized visions of the relationship between nature and culture, protected areas are important sites for understanding how notions of the Anthropocene come to reshape ideas about the future of glaciated landscapes. This article explores one particular conservation initiative, that of the establishment of the tourist and educational facility known as the Route of Climate Change in Peru's Huascarán National Park. It asks how we can understand the production of conservation landscapes in a context where the framing of glaciers as an endangered species denies their fluctuating dynamics and imparts to them a directionality toward irreversible change. Focusing on the contentious production of conservation landscapes through interaction between the park administration and a local community, the article is based on ethnographic fieldwork consisting of semi-structured interviews (48), informal conversations, and participant observation over multiple visits to the area between 2013 and 2015. The study finds that while the production of new conservation narratives certainly resituates the sites in time and place, it also produces uncertain environmental futures that may be molded to secure a rapprochement between park administrations and communities based on mutual alignment of conservation and community practices. It is thus argued that an underlying shift in orientation—from preserving what is to countering what might otherwise come to be—results in the production of new imaginaries about conservation landscapes that are both a condition and an outcome of protected area management in times of glacial retreat. [ABSTRACT FROM AUTHOR]

Many glaciers in alpine regions are currently rapidly receding and thinning at historically unobserved rates causing changes in the velocity field and in normal and shear stresses affecting the surface expression of structures within the ice. We studied the distribution of brittle and ductile structures at the surface of Pasterze Glacier during a 14‐year period by analysing orthophotos and digital elevation models of five stages (1998, 2003, 2006, 2009 and 2012). A structural glaciological mapping key was applied. Normal faults, strike‐slip faults, en échelon structures (systematic stepping of fractures), thrust faults, and band ogives were distinguished. Results indicate substantial deceleration and glacier thinning in 1998–2012. Glacier thinning was not homogenous over time related to the uneven distribution of supraglacial debris causing differential ablation or the selective ablation effects of subglacial water channels. Peculiar supraglacial features observed are circular collapse structures with concentric crevasses which form when the ice between the surface and the roof of water channels decreases. The total length of brittle structures increased from 38.4 km to 56.9 km whereas the extent of the glacier tongue decreased by 25%. The fracture density doubled from 0.009 to 0.018 m/m2. Areas of the glacier tongue which were up to 100 m away from the nearest brittle structure increased by 16%. The visual appearance of thrust faults shifted upglacier due to decreasing glacier velocity causing horizontal shortening or due to exhumation of faults that did not previously extend to the surface. A large number of brittle structures are progressively independent from glacier motion. Our study suggests that glacier tongues which are in a state of rapid decay and thinning are prone to fracturing due to normal fault formation and glacier disintegration. Water further increases ablation rates substantially if rather large amounts drain through supra‐, en‐ or subglacial water channels. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd. Key findings Quantification of supraglacial brittle and ductile structures over a 14 year period (1998‐2012) using remote sensing dataDoubling of the fracture density at the glacier tongue in 14 years from 0.009 to 0.018 m/m2The discontinuous supraglacial debris cover and subglacial ablation related to water streams influenced severely glacier surface changes and fracture evolutionExtension of a time series of brittle structure mapping to 125 years (1887‐2012) with 13 stages at this glacier [ABSTRACT FROM AUTHOR]

This research reveals relationships between climate variables and inter-annual dynamics in the area of the glacieret located in the cirque Golemiya Kazan in the Pirin Mountains. The study period is 1993-2017. The correlations are identified using statistical methods. Also, a statistical model is constructed, including some climate variables as predictors. Despite the evident decrease of the glacieret's size in the period from the 1950s onwards, the long-term trends for the last decades have been insignificant. The main climatic factors influencing the inter-annual dynamics in the area of the glacieret are air temperature, precipitation, zonal and meridional winds and relative humidity. With respect to the dynamics in the area of the glacieret, the important trends in the different climate variables are those of the warm period air temperatures and zonal (u) wind. They also determine to a great extent its future development by acting in two opposite directions-rising temperatures in the warm period will lead to a rapid decrease of its area by the end of the melting season, while the change of wind direction from west to east in the warm period will increase its area. The influence of the zonal wind in the warm period is explained mainly by the location of the glacieret in the cirque. Generally, the glacieret is tilted downwards from west to east. Thus, westerly winds facilitate blowing away the snow from the surface of the glacieret, assisting its melting in the warm period. Easterly winds do not have such an effect. The combination of the opposite effects of these two most important climate variables leads to the most likely scenario for the future development of the glacieret, according to which by the middle of this century it is expected to turn into a semi-permanent snow patch, which disappears after some summers, and by the end of the century to completely melt every year before the end of the melting season. [ABSTRACT FROM AUTHOR]

Abstract The focus of this study is to evaluate the impact of biomass burning (BB) from South Asia and Southeast Asia on the glaciers over the Tibetan Plateau. The seasonality and long-term trend of biomass fires measured by Terra and Aqua satellite data from 2010 to 2016 are used in this study. The analysis shows that the biomass burnings were widely dispersed in the continental of Indian and Southeast Asia and existed a strong seasonal variation. The biomass burnings in winter (January) were relatively weak and scattered and were significantly enhanced in spring (April). The highest biomass burnings located in two regions. One was along the foothill of Himalayas, where is a dense population area, and the second located in Southeast Asia. Because these two high biomass burning regions are close to the Tibetan Plateau, they could have important effects on the BC deposition over the glaciers of the Tibetan Plateau. In order to study the effect of BB emissions on the deposition over the glaciers in the Tibetan Plateau, a regional chemical model (WRF-Chem; Weather Research and Forecasting Chemical model) was applied to simulate the BC distributions and the transport from BB emission regions to the glaciers in Tibetan Plateau. The result shows that in winter (January), due to the relatively weak BB emissions, the effect of BB emissions on BC concentrations was not significant. The BC concentrations resulted from BB emissions ranged from 0.1 to 2.0 μg/m3, with high concentrations distributed along the foothill of Himalayas and the southeastern Asia region. Due to the relative low BC concentrations, there was insignificant effect of BB emissions on the deposition over the glaciers in the Tibetan Plateau in winter. However, the BB emissions were highest in spring (April), producing high BC concentrations. For example, along the Himalayas Mountain and in the southeastern Asia region, The BC concentrations ranged from 2.0 to 6.0 μg/m3. In addition to the high BC concentrations, there were also west and south prevailing winds in these regions. As a result, the BC particles were transported to the glaciers in the Tibetan Plateau, causing significant deposition of BC particles on the snow surface of the glaciers. This study suggests that the biomass burning emissions have important effects on the BC deposition over the glaciers in the Tibetan Plateau, and the contaminations of glaciers could have significant impact on the melting of snow in the Tibetan Plateau, causing some severe environmental problems, such as the water resources. Graphical abstract Unlabelled Image Highlights • Biomass fires in South Asia measured by Terra and Aqua satellite data from 2010 to 2016 are analyzed. • The highest biomass burnings located in two regions (along the foothill of Himalayas and Southeastern Asia) • Biomass burning emissions were highest in spring, producing high BC concentrations (2.0 to 6.0 μg/m3) • BC particles were transported to the glaciers in TP, causing significant deposition on the snow surface of the glaciers [ABSTRACT FROM AUTHOR]

Abstract Proglacial systems are enlarging as glacier masses decline. They are in a transitory state from glacier-dominated to hillslope and fluvially-dominated geomorphological processes. They are a very important meltwater, sediment and solute source. This study makes the first quantitative, systematic and regional assessment of landform composition and functioning within proglacial systems that have developed in the short term since the Little Ice Age (LIA). Proglacial system extent was thus defined as the area between the LIA moraine ridges and the contemporary glacier. We achieved this assessment via a series of topographic analyses of 10 m resolution digital elevation models (DEMs) covering the central European Alps, specifically of Austria and Switzerland. Across the 2812 proglacial systems that have a combined area of 933 km2, the mean proportional area of each proglacial system that is directly affected by glacial meltwater is 37%. However, there are examples where there is no glacial meltwater influence whatsoever due to complete disappearance of glaciers since the LIA, and there are examples where >90% of the proglacial area is probably affected by glacial meltwater. In all of the major drainage basins; the Inn, Drava, Venetian Coast, Po, Rhine, Rhone and Danube, the proportions of the combined land area belonging to each landform class is remarkably similar, with >10% fluvial, ~35% alluvial and debris fans, ~50% moraine ridges and talus/scree, and ~10% bedrock, which will be very helpful for considering estimates of regional sediment yield and denudation rates. We find groupings of the relationship between proglacial system hypsometric index and lithology, and of a slope threshold discriminating between hillslope and fluvial-dominated terrain, both of which we interpret to be due to grain size. We estimate of contemporary total volume loss from all of these proglacial systems of 44 M m3a−1, which equates to a mean of 0.3 mm·a−1 contemporary surface lowering. Overall, these first quantifications of proglacial landform and landscape evolution will be an important basis for inter- and intra-catchment considerations of climate change effects on proglacial systems such as land stability, and changing water, sediment and solute source fluxes. Our datasets are made freely available. Highlights • Delineation of 2812 proglacial systems in central European Alps of total 933 km2 • Glacier meltwater and landform coverage spatially discriminated for each system • Lithological control evident in slope threshold – contributing area analysis • First order estimate of total contemporary volume loss = 44 M m3a−1 [ABSTRACT FROM AUTHOR]

Abstract: Glacier retreat is a key component of environmental change in alpine environments, leading to significant changes in physico‐chemical characteristics and biological communities in glacier‐fed rivers. While the overall effects of the environment on community structure of invertebrates are largely understood, its influence on functional strategies such as feeding habits of same species are not. The aquatic larvae of the species‐rich family Chironomidae, or nonbiting midges, are the first invertebrates colonising alpine headwaters, and the first macroinvertebrate consumers in these harsh environments. Species composition in the two subfamilies, Diamesinae and Orthocladiinae, is diverse and is strongly affected by the changing habitat conditions upon glacier retreat. Here, we show that Diamesinae have extremely flexible feeding strategies that explain their abundance, high body‐mass and predominance in glacier‐fed streams. Along a multifactorial ecological gradient from benign to harsh, based on water temperature, sediment transport and degree of glacial influence, Diamesinae expanded their trophic niche area and covered more trophic levels when conditions harshened. In contrast, niche areas of Orthocladiinae remained small and were not related to this gradient. In Diamesinae, mean body‐mass increased with harsher environmental conditions, but no such effects were found in Orthocladiinae. As facultative predators and able to feed on diverse food sources, Diamesinae have evolved survival mechanisms that allow them to thrive and successfully reproduce in glacier‐fed streams, which likely explains their predominance in these habitats. Climate change‐induced glacier retreat affects the global water balance, with many downstream effects, including on irrigation and domestic use, and our study deepens our understanding of its effects on animals that depend on glacier‐melt. [ABSTRACT FROM AUTHOR]

This paper reports that in the period of global warming continuing over 150 years, there are the glaciers growing in size. [ABSTRACT FROM AUTHOR]

The Sierra de Famatina is considered the highest elevation outside the Argentine Andes Cordillera, being the General Belgrano hill, 6097 masl, the main height. This altitudinal situation favored the development of glaciers during the cold events of the cyclical Quaternary climatic fluctuations, giving shape to a territory with very complex morphologies. The aim of this contribution is to describe the current and past geomorphological processes in the vicinity of the highest sector of the Sierra de Famatina through different forms of the landscape, which put together allow the recognition of the geomorphological evolution of the region. At present, extreme weather lead to periglacial conditions above 4000 m and glacial above 6000 m, generating ice and snow patches almost without movements in flat to flat-concave sections of the watersheds, and rock glaciers, gelifluction lobes and earth hummocks in cirques, troughs and walls of valleys. Depending on the features of glacial accumulation, three cold events can be recognized, the youngest one (MIS2) with limited distribution, is restricted to the heads of troughs and cirques, from whose deposits the rock glaciers develop. The second one, observed near Puesto Tres Piedras, is represented by moraine-shaped glacier deposits above 3000 m height, and would belong to the Middle-Late Pleistocene. The oldest glacier deposits, early-middle Pleistocene, are in higher topographies. Below 3000 m, valleys are rocky and steep-sided, with permanent courses due not only to low rainfall, but mainly to the melting of the permafrost, forming important reservoirs of water. [ABSTRACT FROM AUTHOR]

Marine-terminating ice sheets are of interest due to their potential instability, making them vulnerable to rapid retreat. Modelling the evolution of glaciers and ice streams in such regions is key to understanding their possible contribution to sea level rise. The friction caused by the sliding of ice over bedrock and the resultant shear stress are important factors in determining the velocity of sliding ice. Many models use simple power-law expressions for the relationship between the basal shear stress and ice velocity or introduce an effective-pressure dependence into the sliding relation in an ad hoc manner. Sliding relations based on waterfilled subglacial cavities are more physically motivated, with the overburden pressure of the ice included. Here we show that using a cavitation-based sliding relation allows for the temporary regrounding of an ice shelf at a point downstream of the main grounding line of a marine ice sheet undergoing retreat across a retrograde bedrock slope. This suggests that the choice of sliding relation is especially important when modelling grounding line behaviour of regions where potential ice rises and pinning points are present and regrounding could occur. [ABSTRACT FROM AUTHOR]

Stratospheric aerosol geoengineering, a form of solar geoengineering, is a proposal to add a reflective layer of aerosol to the stratosphere to reduce net radiative forcing and so to reduce the risks of climate change. The efficacy of solar geoengineering at reducing changes to the cryosphere is uncertain; solar geoengineering could reduce temperatures and so slow melt, but its ability to reverse ice sheet collapse once initiated may be limited. Here we review the literature on solar geoengineering and the cryosphere and identify the key uncertainties that research could address. Solar geoengineering may be more effective at reducing surface melt than a reduction in greenhouse forcing that produces the same global-average temperature response. Studies of natural analogues and model simulations support this conclusion. However, changes below the surfaces of the ocean and ice sheets may strongly limit the potential of solar geoengineering to reduce the retreat of marine glaciers. High-quality process model studies may illuminate these issues. Solar geoengineering is a contentious emerging issue in climate policy and it is critical that the potential, limits, and risks of these proposals are made clear for policy makers. [ABSTRACT FROM AUTHOR]

Over the past 20 years satellite remote sensing has captured significant downwasting of glaciers that drain the West Antarctic Ice Sheet into the ocean, particularly across the Amundsen Sea Sector. Along the neighbouring Marie Byrd Land Sector, situated west of Thwaites Glacier to Ross Ice Shelf, glaciological change has been only sparsely monitored. Here, we use optical satellite imagery to track grounding-line migration along the Marie Byrd Land Sector between 2003 and 2015, and compare observed changes with ICESat and CryoSat-2-derived surface elevation and thickness change records. During the observational period, 33% of the grounding line underwent retreat, with no significant advance recorded over the remainder of the ~2200 km long coastline. The greatest retreat rates were observed along the 650 km-long Getz Ice Shelf, further west of which only minor retreat occurred. The relative glaciological stability west of Getz Ice Shelf can be attributed to a divergence of the Antarctic Circumpolar Current from the continental-shelf break at 135°W, coincident with a transition in the morphology of the continental shelf. Along Getz Ice Shelf, grounding-line retreat reduced by 68% during the CryoSat- 2 era relative to earlier observations. Climate reanalysis data imply that wind-driven upwelling of Circumpolar Deep Water would have been reduced during this later period, suggesting that the observed slowdown was a response to reduced oceanic forcing. However, lack of comprehensive oceanographic and bathymetric information proximal to Getz Ice Shelf's grounding zone make it difficult to assess the role of intrinsic glacier dynamics, or more complex ice-sheet- ocean interactions, in moderating this slowdown. Collectively, our findings underscore the importance of spatial and inter-decadal variability in atmosphere and ocean interactions in moderating glaciological change around Antarctica. [ABSTRACT FROM AUTHOR]

In order to derive long-term changes in sea-ice volume, a multi-decadal sea-ice thickness record is required. CryoSat-2 has showcased the potential of radar altimetry for sea-ice mass-balance estimation over the recent years. However, precursor altimetry missions such as Environmental Satellite (Envisat) have not been exploited to the same extent so far. Combining both missions to acquire a decadal sea-ice volume data set requires a method to overcome the discrepancies due to different footprint sizes from either pulselimited or beam-sharpened radar echoes. In this study, we implemented an inter-mission-consistent surface-type classification scheme for both hemispheres, based on the waveform pulse peakiness, leading-edge width, and surface backscatter. In order to achieve a consistent retracking procedure, we adapted the threshold first-maximum retracker algorithm, previously used only for CryoSat-2, to develop an adaptive retracker threshold that depends on waveform characteristics. With our method, we produce a global and consistent freeboard data set for CryoSat-2 and Envisat. This novel data set features a maximum monthly difference in the missionoverlap period of 2.2 cm (2.7 cm) for the Arctic (Antarctic) based on all gridded values with spatial resolution of 25kmx25km and 50kmx50km for the Arctic and Antarctic, respectively. [ABSTRACT FROM AUTHOR]

An accurate chronology is the essential first step for a sound understanding of ice core records. However, dating ice cores drilled from the high-elevation glaciers is challenging and often problematic, leading to great uncertainties. The Guliya ice core, drilled to the bedrock (308.6m in length) along the western Kunlun Mountains on the northwestern Tibetan Plateau (TP) and widely used as a benchmark for palaeoclimate research, is believed to reach > 500 ka (thousand years) at its bottom. Meanwhile other Tibetan ice cores (i.e. Dasuopu and East Rongbuk in the Himalayas, Puruogangri in the central TP and Dunde in the north-eastern TP) are mostly of Holocene origin. In this study, we drilled four ice cores into bedrock (216.6, 208.6, 135.8 and 133.8m in length, respectively) from the Chongce ice cap ~ 30 km to the Guliya ice core drilling site. We took measurements of 14C, 210Pb, tritium and β activity for the ice cores, and used these values in a two-parameter flow model to establish the ice core depth-age relationship. We suggested that the Chongce ice cores might be of Holocene origin, consistent with the other Tibetan ice cores except Guliya. The remarkable discrepancy between the Guliya and all the other Tibetan ice core chronology implies that more effort is necessary to explore multiple dating techniques to confirm the age ranges of the TP glaciers, including those from Chongce and Guliya. [ABSTRACT FROM AUTHOR]

Knowledge of backscatter change is important to accurately retrieve elevation change time series from satellite radar altimetry over continental ice sheets. Previously, backscatter coefficients generated in two cases, namely with and without accounting for backscatter gradient (BG), are used. However, the difference between backscatter time series obtained separately in these two cases and its impact on retrieving elevation change are not well known. Here we first compare the mean profiles of the Ku and Ka band backscatter over the Greenland ice sheet (GrIS), with results illustrating that the Ku-band backscatter is 3 ∼ 5 dB larger than that of the Ka band. We then conduct statistic analysis about time series of backscatter formed separately in the above two cases for both Ku and Ka bands over two regions in the GrIS. It is found that the standard deviation of backscatter time series becomes slightly smaller after removing the BG effect, which suggests that the method for the BG correction is effective. Furthermore, the impact on elevation change from backscatter change due to the BG effect is separately assessed for both Ku and Ka bands over the GrIS. We conclude that Ka band altimetry would benefit from a BG induced backscatter analysis (∼10% over region 2). This study may provide a reference to form backscatter time series towards refining elevation change time series from satellite radar altimetry over ice sheets using repeat-track analysis. [ABSTRACT FROM AUTHOR]

While glacier mass changes in the Himalaya since the year 2000 are relatively well investigated, there is still a lack of knowledge about the long-term changes and their climatic drivers. We use historical and recent remote sensing data to study glacier changes of the Lahaul-Spiti region in western Himalaya, India, over the last four decades (1971-2013). The glaciers were losing mass moderately between 1971 and 1999 (− 0.07 ± 0.1 m w.e. year−1) while the losses have increased significantly after 2000 (− 0.30 ± 0.1 m w.e. year−1). During both periods, the debris-covered glaciers and glaciers having pro-glacial lakes lost more mass than glaciers with little debris cover. Mass changes of Chhota Shigri, a benchmark glacier, closely matched the average of the overall study area. Analysis of gridded climate data covering the period 1948-2015 shows that the mean annual air temperature increased, especially since 1995. One dataset shows a significant increase in summer temperature after 2000 while others do not show any trend. The mean annual precipitation started decreasing around 1995 and reached a minimum around 2000, after which it increased again. One dataset shows a significant decrease in winter precipitation after 2000 while the others show no trend. The climate data indicate that the increase in mean annual temperature from 1995, combined with no significant trend/significant decrease of winter precipitation in the period after 2000, has probably resulted in accelerated mass loss of the glaciers. [ABSTRACT FROM AUTHOR]

Despite recent research identifying a clear anthropogenic impact on glacier recession, the effect of recent climate change on glacier-related hazards is at present unclear. Here we present the first global spatio-temporal assessment of glacial lake outburst floods (GLOFs) focusing explicitly on lake drainage following moraine dam failure. These floods occur as mountain glaciers recede and downwaste. GLOFs can have an enormous impact on downstream communities and infrastructure. Our assessment of GLOFs associated with the rapid drainage of moraine-dammed lakes provides insights into the historical trends of GLOFs and their distributions under current and future global climate change. We observe a clear global increase in GLOF frequency and their regularity around 1930, which likely represents a lagged response to post-Little Ice Age warming. Notably, we also show that GLOF frequency and regularity - rather unexpectedly - have declined in recent decades even during a time of rapid glacier recession. Although previous studies have suggested that GLOFs will increase in response to climate warming and glacier recession, our global results demonstrate that this has not yet clearly happened. From an assessment of the timing of climate forcing, lag times in glacier recession, lake formation and moraine-dam failure, we predict increased GLOF frequencies during the next decades and into the 22nd century. [ABSTRACT FROM AUTHOR]

Because of the harsh weather conditions on the Antarctic continent, year-round observations of the lowlevel boundary layer must be obtained via automated data acquisition systems. Alexander Tall Tower! is an automatic weather station on the Ross Ice Shelf in Antarctica and has been operational since February 2011. At 30m tall, this station has six levels of instruments to collect environmental data, including temperature, wind speed and direction, relative humidity, and pressure. Data are collected at 30-, 15-, 7.5-, 4-, 2-, and 1-m levels above the snow surface. This study identifies short-term trends and provides an improved description of the lowest portion of the boundary layer over this portion of the Ross Ice Shelf for the February 2011-January 2014 period. Observations indicate two separate initiations of the winter season occur annually, caused by synoptic-scale anomalies. Sensible and latent heat flux estimates are computed using Monin-Obukhov similarity theory and vertical profiles of potential air temperature and wind speed. Over the three years, the monthly mean sensible heat flux ranges between 1 and 39 W m-2 (toward the surface) and the monthly mean latent heat flux ranges between -8 and 0 W m-2. Net heat fluxes directed toward the surface occur most of the year, indicating an atmospheric sink of energy. [ABSTRACT FROM AUTHOR]

We present a comprehensive review of the status and changes in glacier length (since the 1850s), area and mass (since the 1960s) along the Himalayan-Karakoram (HK) region and their climate-change context. A quantitative reliability classification of the field-based mass-balance series is developed. Glaciological mass balances agree better with remotely sensed balances when we make an objective, systematic exclusion of likely flawed mass-balance series. The Himalayan mean glaciological mass budget was similar to the global average until 2000, and likely less negative after 2000. Mass wastage in the Himalaya resulted in increasing debris cover, the growth of glacial lakes and possibly decreasing ice velocities. Geodetic measurements indicate nearly balanced mass budgets for Karakoram glaciers since the 1970s, consistent with the unchanged extent of supraglacial debris-cover. Himalayan glaciers seem to be sensitive to precipitation partly through the albedo feedback on the short-wave radiation balance. Melt contributions from HK glaciers should increase until 2050 and then decrease, though a wide range of present-day area and volume estimates propagates large uncertainties in the future runoff. This review reflects an increasing understanding of HK glaciers and highlights the remaining challenges. [ABSTRACT FROM PUBLISHER]

Dating ice cores drilled in the high mountain glaciers is difficult because seasonal variations cannot be traced at depth due to rapid thinning of the ice layers. Here we provide the first luminescence dating of the basal sediment of the Chongce ice cap in the north-western Tibetan Plateau. Assuming the sediment is of similar (or older) age as the surrounding ice, the luminescence dating of 42±4 ka provides an upper constraint for the age of the bottom ice at the drilling site. This result is more than 1 order of magnitude younger than the previously suggested age of the basal ice of the nearby Guliya ice cap (~40 km in distance). [ABSTRACT FROM AUTHOR]

Less than 0.25% of the 250 000 glaciers inventoried in the Randolph Glacier Inventory (RGI V.5) are currently monitored with in situ measurements of surface mass balance. Increasing this archive is very challenging, especially using time-consuming methods based on in situ measurements, and complementary methods are required to quantify the surface mass balance of unmonitored glaciers. The current study relies on the so-called albedo method, based on the analysis of albedo maps retrieved from optical satellite imagery acquired since 2000 by the MODIS sensor, on board the TERRA satellite. Recent studies revealed substantial relationships between summer minimum glacier-wide surface albedo and annual surface mass balance, because this minimum surface albedo is directly related to the accumulation-area ratio and the equilibrium-line altitude. On the basis of 30 glaciers located in the French Alps where annual surface mass balance data are available, our study conducted on the period 2000-2015 confirms the robustness and reliability of the relationship between the summer minimum surface albedo and the annual surface mass balance. For the ablation season, the integrated summer surface albedo is significantly correlated with the summer surface mass balance of the six glaciers seasonally monitored. These results are promising to monitor both annual and summer glacier-wide surface mass balances of individual glaciers at a regional scale using optical satellite images. A sensitivity study on the computed cloud masks revealed a high confidence in the retrieved albedo maps, restricting the number of omission errors. Albedo retrieval artifacts have been detected for topographically incised glaciers, highlighting limitations in the shadow correction algorithm, although interannual comparisons are not affected by systematic errors. [ABSTRACT FROM AUTHOR]

Glaciers with extensive surface debris cover respond differently to climate forcing than those without supraglacial debris. In order to include debris-covered glaciers in projections of glaciogenic runoff and sea level rise and to understand the paleoclimate proxy recorded by such glaciers, it is necessary to understand the manner and timescales over which a supraglacial debris cover develops. Because debris is delivered to the glacier by processes that are heterogeneous in space and time, and these debris inclusions are altered during englacial transport through the glacier system, correctly determining where, when and how much debris is delivered to the glacier surface requires knowledge of englacial transport pathways and deformation. To achieve this, we present a model of englacial debris transport in which we couple an advection scheme to a full-Stokes ice flow model. The model performs well in numerical benchmark tests, and we present both 2-D and 3-D glacier test cases that, for a set of prescribed debris inputs, reproduce the englacial features, deformation thereof and patterns of surface emergence predicted by theory and observations of structural glaciology. In a future step, coupling this model to (i) a debris-aware surface mass balance scheme and (ii) a supraglacial debris transport scheme will enable the co-evolution of debris cover and glacier geometry to be modelled. [ABSTRACT FROM AUTHOR]

Stable isotope ratios δ18O and δD in polar ice provide a wealth of information about past climate evolution. Snow-pit studies allow us to relate observed weather and climate conditions to the measured isotope variations in the snow. They therefore offer the possibility to test our understanding of how isotope signals are formed and stored in firn and ice. As δ18O and δD in the snowfall are strongly correlated to air temperature, isotopes in the near-surface snow are thought to record the seasonal cycle at a given site. Accordingly, the number of seasonal cycles observed over a given depth should depend on the accumulation rate of snow. However, snow-pit studies from different accumulation conditions in East Antarctica reported similar isotopic variability and comparable apparent cycles in the δ18O and δD profiles with typical wavelengths of ~20 cm. These observations are unexpected as the accumulation rates strongly differ between the sites, ranging from 20 to 80mmw:e: yr-1 (~6-21 cm of snow per year). Various mechanisms have been proposed to explain the isotopic variations individually at each site; however, none of these are consistent with the similarity of the different profiles independent of the local accumulation conditions. Here, we systematically analyse the properties and origins of δ18O and δD variations in high-resolution firn profiles from eight East Antarctic sites. First, we confirm the suggested cycle length (mean distance between peaks) of ~20 cm by counting the isotopic maxima. Spectral analysis further shows a strong similarity between the sites but indicates no dominant periodic features. Furthermore, the apparent cycle length increases with depth for most East Antarctic sites, which is inconsistent with burial and compression of a regular seasonal cycle. We show that these results can be explained by isotopic diffusion acting on a noise-dominated isotope signal. The firn diffusion length is rather stable across the Antarctic Plateau and thus leads to similar power spectral densities of the isotopic variations. This in turn implies a similar distance between isotopic maxima in the firn profiles. Our results explain a large set of observations discussed in the literature, providing a simple explanation for the interpretation of apparent cycles in shallow isotope records, without invoking complex mechanisms. Finally, the results underline previous suggestions that isotope signals in single ice cores from low-accumulation regions have a small signal-to-noise ratio and thus likely do not allow the reconstruction of interannual to decadal climate variations. [ABSTRACT FROM AUTHOR]

Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate) glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glaciallake outburst floods (GLOFs). Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs) derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM) (2000) and from TerraSAR-X/TanDEM-X (2014), this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETMC/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048:50±48:65 km2 in 2015. Ice cover diminished by 679:51±59:49 km2 (24:9±2:2%) or 0:71±0:06%a-1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0:46±0:08mw:e: a-1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980-2000, consistent with a warming climate. [ABSTRACT FROM AUTHOR]

Glacier surges occur regularly in the Karakoram, but the driving mechanisms, their frequency and its relation to a changing climate remain unclear. In this study, we use digital elevation models and Landsat imagery in combination with high-resolution imagery from the Planet satellite constellation to quantify surface elevation changes and flow velocities during a glacier surge of the Khurdopin Glacier in 2017. Results reveal that an accumulation of ice volume above a clearly defined steep section of the glacier tongue since the last surge in 1999 eventually led to a rapid surge in May 2017 peaking with velocities above 5000ma-1, which were among the fastest rates globally for a mountain glacier. Our data reveal that velocities on the lower tongue increase steadily during a 4-year build-up phase prior to the actual surge only to then rapidly peak and decrease again within a few months, which confirms earlier observations with a higher frequency of available velocity data. The surge return period between the reported surges remains relatively constant at ca. 20 years. We show the potential of a combination of repeat Planet and ASTER imagery to (a) capture peak surge velocities that are easily missed by less frequent Landsat imagery, (b) observe surface changes that indicate potential drivers of a surge and (c) monitor hazards associated with a surge. At Khurdopin specifically, we observe that the surging glacier blocks the river in the valley and causes a lake to form, which may grow in subsequent years and could pose threats to downstream settlements and infrastructure in the case of a sudden breach. [ABSTRACT FROM AUTHOR]

There have been numerous studies of glaciers in the Greater Caucasus, but none that have generated a modern glacier database across the whole mountain range. Here, we present an updated and expanded glacier inventory at three time periods (1960, 1986, 2014) covering the entire Greater Caucasus. Large-scale topographic maps and satellite imagery (Corona, Landsat 5, Landsat 8 and ASTER) were used to conduct a remote-sensing survey of glacier change, and the 30m resolution Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM; 17 November 2011) was used to determine the aspect, slope and height distribution of glaciers. Glacier margins were mapped manually and reveal that in 1960 the mountains contained 2349 glaciers with a total glacier surface area of 1674.9±70.4 km2. By 1986, glacier surface area had decreased to 1482.1±64.4 km2 (2209 glaciers), and by 2014 to 1193.2±54.0 km2 (2020 glaciers). This represents a 28.8±4.4% (481±21.2 km2) or 0.53%yr-1 reduction in total glacier surface area between 1960 and 2014 and an increase in the rate of area loss since 1986 (0.69%yr-1) compared to 1960-1986 (0.44%yr-1). Glacier mean size decreased from 0.70 km2 in 1960 to 0.66 km2 in 1986 and to 0.57 km2 in 2014. This new glacier inventory has been submitted to the Global Land Ice Measurements from Space (GLIMS) database and can be used as a basis data set for future studies. [ABSTRACT FROM AUTHOR]

Though being considered strategically important in matters of national defense based on its abundance of natural resources, Northwest China is one of the most ecologically vulnerable areas in the country. As one of the region's important water sources, glaciers have gone through major changes due to climate change. An analysis of research results over the past 60 years reveals that the glaciers have been retreating in general to some degree in large river basins in Northwest China, but the rate of retreating varied largely among different regions, ranging from 0.01% • a-1 to 0.75% . a-1. Specifically, glaciers around the Lantsang River Basin and the Altay Mountains have bean retreating fastest. The retreat of glaciers has already caused an increase in runoff in mountainous areas of Northwest China. Meanwhile, increases in the frequency of glacial flash floods and in the flood discharge will further enhance the probability of glacial lake outburst floods and ensuing disasters. [ABSTRACT FROM AUTHOR]

Many large valley glaciers in the world are retreating at historically unprecedented rates. Also in the Alps, where warming over the past decades has been more than twice as large as the global mean, all major glaciers have retreated over distances of several kilometers over the past hundred years. The Morteratsch Glacier, Pontresina, Switzerland, is a major touristic attraction. Due to strong retreat, the lowest part of the glacier is getting out of sight from the gravel road that provided direct access to the glacier front. The Community of Pontresina has commissioned a preparatory study to find out if it is possible to slow down the retreat of the Morteratsch Glacier in an environmentally friendly way. In this article, we report on the outcome of such a study, based on a modeling approach. Our analysis is based on a 20-year weather station record from the lower part of the glacier, combined with calculations with a calibrated ice-flow model. We arrive at the conclusion that producing summer snow in the ablation zone over a larger area (typically 0.5 to 1 km) may have a significant effect on the rate of retreat on a timescale of decades. We consider various scenarios of climate change: (i) no change, (ii) a rise of the equilibrium-line altitude (ELA) by 1, 2, and 4 m/yr. Projections of glacier length are calculated until the year 2100. It takes about 10 years before snow deposition in the higher ablation zone starts to affect the position of the glacier snout. For the case of modest warming, the difference in glacier length between the snow and no-snow experiments becomes 400 to 500 m within two decades. [ABSTRACT FROM AUTHOR]

Temporal changes in the properties of glaciers located on the central Tibetan Plateau are a sensitive indicator of climate change and the water supply. To estimate the region-wide glacier budgets for three study sites covering the region extending from West- Geladandong to Bugyai Kangri, we compared 1968/1969 topographic maps, the 2000 SRTM DEM, and recent ASTER DEMs for glacier mass budget calculations. Between ∼1969 and ∼2015, the specific mass budget was -0.31 ± 0.05 m w.e. a-1 for the entire Tanggula Mountains, which is lower than the global average. This ongoing mass loss is mainly caused by increasing summer temperatures since the 1960s. Heterogeneous glacier behavior can be explained by a combination of factors, including meteorological conditions, proglacial lakes, and surge-type glaciers. [ABSTRACT FROM AUTHOR]

Records of Neoglacial glacier activity in the Arctic constructed from moraines are often incomplete due to a preservation bias toward the most extensive advance, often the Little Ice Age. Recent warming in the Arctic has caused extensive retreat of glaciers over the past several decades, exposing preserved landscapes complete with in situ tundra plants previously entombed by ice. The radiocarbon ages of these plants define the timing of snowline depression and glacier advance across the site, in response to local summer cooling. Erosion rapidly removes most dead plants that have been recently exposed by ice retreat, but where erosive processes are unusually weak, dead plants may remain preserved on the landscape for decades. In such settings, a transect of plant radiocarbon ages can be used to construct a nearcontinuous chronology of past ice margin advance. Here we present radiocarbon dates from the first such transect on Baffin Island, which directly dates the advance of a small ice cap over the past two millennia. The nature of ice expansion between 20 BCE and ~1000 CE is still uncertain, but episodic advances at ~1000 CE, ~1200, and ~1500 led to the maximum Neoglacial dimensions ~1900 CE.We employ a two-dimensional numerical glacier model calibrated using the plant radiocarbon ages ice margin chronology to assess the sensitivity of the ice cap to temperature change. Model experiments show that at least ~0.44 °C of cooling over the past 2 kyr is required for the ice cap to reach its 1900 CE margin, and that the period from ~1000 to 1900 CE must have been at least 0.25° C cooler than the previous millennium, results that agree with regional temperature reconstructions and climate model simulations. However, significant warming since 1900 CE is required to explain retreat to its present position, and, at the same rate of warming, the ice cap will disappear before 2100 CE. [ABSTRACT FROM AUTHOR]

Glaciers are significant freshwater storage systems in western China and contribute substantially to the summertime run-off of many large rivers in the Tibetan Plateau. Under the scenario of climate change, discussions of glacier variability and melting contributions in alpine basins are important for understanding the run-off composition and ensuring that water resources are adequately managed and protected in the downstream areas. Based on the multisource spatial data and long-term ground observation of climatic and hydrologic data, using the remote sensing interpretation, degree-day model, and ice volume method, we presented a comprehensive study of the glacier changes in number, area, and termini and their impacts on summertime run-off and water resource in the Tuotuo River basin, located in the source region of the Yangtze River. The results indicated that climate change, especially rising temperature, accelerated the glacier melting and consequently led to hydrological change. From 1969 to 2009, the glacier retreat showed an absolutely dominant tendency with 13 reduced glaciers and lost glacier area of 45.05 km2, accompanied by limited growing glaciers in the study area. Meanwhile, it indicated that annual glacial run-off was averagely 0.38 × 108 m3, accounting for 4.96% of the total summertime run-off, followed by the supply from precipitation and snowmelt. The reliability of this magnitude was assessed by the classic volume method, which also showed that the water resources from glacier melting in the Tuotuo River basin increased by approximate 17.11 × 108 m3, accounting for about 3.77% of the total run-off over the whole period of 1969-2009. Findings from this study will serve as a reference for future research about glacier hydrology in regions where observational data are deficient. Also, it can help the planning of future water management strategies in the source region of the Yangtze River. [ABSTRACT FROM AUTHOR]

Whether coupling auxiliary information (except for conventional rainfall-runoff and temperature data) into hydrological models can improve model performance and transferability is still an open question. In this study, we chose a glacier catchment to test the effect of auxiliary information, i.e., distributed forcing input, topography, snow-ice accumulation and melting on model calibration-validation and transferability. First, we applied the point observed precipitation and temperature as forcing data, to test the model performance in calibration-validation and transferability. Second, we took spatial distribution of forcing data into account, and did the same test. Third, the aspect was involved to do an identical experiment. Finally, the snow-ice simulation was used as part of the objective function in calibration, and to conduct the same experiment. Through stepwisely accounting these three pieces of auxiliary information, we found that a model without involving forcing data distribution, local relief, or snow-ice data can also perform well in calibration, but adding forcing data distribution and topography can dramatically increase model validation and transferability. It is also remarkable that including the snow-ice simulation into objective function did not improve model performance and transferability in this study. This may be because the well-gauged hydro-meteorological data are sufficient to constrain a well-designed hydrological model. [ABSTRACT FROM AUTHOR]

How do glaciers move? This seemingly straightforward question provided the backdrop for a heated debate between the physicists John Tyndall (1820–1893) and James David Forbes (1809–1868) in the late 1850s and early 1860s. Forbes described the motion of glaciers as that of a viscous fluid. After visiting the Alps, Tyndall proposed an alternative theory that combined fracture and regelation. The glacial controversy ensued. Yet the debate was never simply about whether glaciers moved like honey, or if they moved by continuously breaking and re-attaching. This paper shows that the glacial controversy formed an important prelude to the strategies used by the X-Club in reforming science and establishing cultural authority. There was a central difference in the way Forbes and Tyndall presented their scientific arguments. Tyndall and his allies used the changes in the periodical press as part of their strategy for establishing and maintaining cultural and scientific authority. By contrast, Forbes and his supporters, including the North British physicists, were not as quick to make use of this new medium. This paper, therefore, examines in detail the significance of these two publishing strategies in shaping the nature and results of the glacial controversy. [ABSTRACT FROM AUTHOR]

Climate change is driving the thinning and retreat of many glaciers globally. Reductions of ice-melt inputs to mountain rivers are changing their physicochemical characteristics and, in turn, aquatic communities. Glacier-fed rivers can serve as model systems for investigations of climate-change effects on ecosystems because of their strong atmospheric-cryospheric links, high biodiversity of multiple taxonomic groups, and significant conservation interest concerning endemic species. From a synthesis of existing knowledge, we develop a new conceptual understanding of how reducing glacier cover affects organisms spanning multiple trophic groups. Although the response of macroinvertebrates to glacier retreat has been well described, we show that there remains a relative paucity of information for biofilm, microinvertebrate, and vertebrate taxa. Enhanced understanding of whole river food webs will improve the prediction of river-ecosystem responses to deglaciation while offering the potential to identify and protect a wider range of sensitive and threatened species. [ABSTRACT FROM AUTHOR]

Rapid regional warming in the Antarctic Peninsula has led to the significant retreat and eventual collapse of several major ice shelves since the 1970s, triggering the subsequent acceleration and thinning of their feeding glaciers. The Wordie Ice Shelf, lying off the west coast of the Antarctic Peninsula, has undergone long-term disintegration since the 1960s with a substantial calving event occurring around 1989, followed by continuous steady retreat and its almost-complete disappearance. The dynamic response of the upstream glaciers to the ice shelf collapse and the response of the solid Earth to the associated mass loss are not fully understood. To quantify the mass loss from the system, we generated a digital elevation model (DEM) using airborne vertical and oblique imagery from 1966 and compared it to a DEM derived from 2008 SPOT data. This analysis reveals lowering over that time of approximately 60 m at the front of Fleming Glacier. Using IceBridge and ICESat-2/GLAS data spanning 2002–2014, we show an increased rate of mean ice-surface lowering, with rates post-2008 more than twice those of 2002–2008. We use these load change data as a basis for the simulation of viscoelastic solid Earth deformation. We subtract modeled elastic deformation rates, and a suite of modeled viscous rates, from GPS-derived three-dimensional bedrock velocities at sites to the south of Fleming Glacier to infer properties of Earth rheology. Assuming the pre-breakup bedrock uplift was positive due to post-Last Glacial Maximum (LGM) ice retreat, our viscoelastic-corrected GPS uplift rates suggest upper mantle viscosities are > 2 × 10 19 Pa s and likely > 1 × 10 20 Pa s in this region, 1–2 orders of magnitude greater than previously found for the northern Antarctic Peninsula. Horizontal velocities at the GPS site nearest the Fleming Glacier, after the application of elastic and plate tectonic corrections, point away from Marguerite Bay rather than the present glacier front. This suggests that horizontal motion in the region reflects the earlier retreat of the glacier system following the LGM, compatible with a relatively strong mantle in this region. These findings highlight the need for improved understanding of ice load changes in this region through the late Holocene in order to accurately model glacial isostatic adjustment. [ABSTRACT FROM AUTHOR]

Glaciers in the Himalayan Mountain system are undergoing rapid retreat, and the global climate change has a significant impact on it. In the present study, we used stable water isotope and remote sensing data to understand the impact of climate on melting behavior of some high-altitude glaciers in two glacier-fed basins of western Himalaya, India. Glacier samples were collected from four major glaciers of Liddar (Kashmir region) and Suru basins (Ladakh region) during melting season from May 2012 to November 2013 for δO and δH. It was observed that the glacier samples from Suru basin were more depleted in O and H (−10.9 to −16.2‰ and −73 to −128‰) than the glaciers of Liddar basin (−8.2 to −14.9‰ and −52 to −102‰). However, the d-excess of the glacier samples in Suru basin was lower (13.5-21.6‰) than the glaciers of Liddar basin (17-28‰). It was observed that the temporal changes in weather pattern strongly influence the isotopic composition of the glaciers with progressive decrease and increase in δO (or δH) with the increase in ambient temperature and rainfall, respectively. The results suggest that during the sunny days of August and September, the glaciers are melting at higher altitudes (3900-4172 m) in the accumulation zone, reflecting that the glaciers of Liddar basin are not the ideal sites for the ice coring for paleoclimatological studies. The study also revealed that 20% glacier extent (glacierized area) in Liddar basin has been lost in <35 years, which is quite higher than that of Suru basin (2%). [ABSTRACT FROM AUTHOR]

In this review, we summarized the evolution of glacier monitoring in the tropical Andes during the last few decades, particularly after the development of remote sensing and photogrammetry. Advantages and limitations of glacier mapping, applied so far, in Venezuela, Colombia, Ecuador, Peru and Bolivia are discussed in detail. Glacier parameters such as the equilibrium line altitude, snowline and mass balance were given special attention in understanding the complex cryosphere-climate interactions, particularly using remote sensing techniques. Glaciers in the inner and the outer tropics were considered separately based on the precipitation and temperature conditions within a new framework. The applicability of various methods to use glacier records to understand and reconstruct the tropical Andean climate between the Last Glacial Maximum (11,700 years ago) and the present is also explored in this paper. Results from various studies published recently were analyzed and we tried to understand the differences in the magnitudes of glacier responses towards the climatic perturbations in the inner tropics and the outer tropics. Inner tropical glaciers, particularly those in Venezuela and Colombia near the January Intertropical Convergence Zone (ITCZ), are more vulnerable to increase in temperature. Surface energy balance experiments show that outer tropical glaciers respond to precipitation variability very rapidly in comparison with the temperature variability, particularly when moving towards the subtropics. We also analyzed the gradients in glacier response to climate change from the Pacific coast towards the Amazon Basin as well as with the elevation. Based on the current trends synthesised from recent studies, it is hypothesized that the glaciers in the inner tropics and the southern wet outer tropics will disappear first as a response to global warming whereas glaciers in the northern wet outer tropics and dry outer tropics show resistance to warming trends due to the occurrence of cold phases of El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) together. Mountain glaciers in Ecuador show less retreat in response to the warming trend, probably due to high altitudes (above 5750 m), in comparison to glaciers in Colombia and Venezuela. However, elevation-dependent warming (EDW) is a major concern in the tropical Andes. In a nutshell, smaller glaciers at lower altitudes in the inner tropics and the southern wet outer tropics near the Amazon Basin are disappearing faster than other glaciers in the tropical Andes. [ABSTRACT FROM AUTHOR]