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As the world's glaciers recede in response to a warming atmosphere, a change in the magnitude and frequency of related hazards is expected. Among the most destructive hazards are glacier lake outburst floods (GLOFs), and their future evolution is concerning for local populations and sustainable development policy. Central to this is a better understanding of triggers. There is a long‐standing assumption that earthquakes are a major GLOF trigger, and seismic activity is consistently included as a key hazard assessment criterion. Here, we provide the first empirical evidence that this assumption is largely incorrect. Focusing on the Tropical Andes, we show that, of 59 earthquakes (1900–2021) the effects of which intersect with known glacier lakes, only one has triggered GLOFs. We argue that, to help develop climate resilient protocols, the focus for future assessments should be on understanding other key GLOF drivers, such as thawing permafrost and underlying structural geology. Plain Language Summary: Climate change is increasing glacier melt in high mountains and increasing the size and number of glacial lakes. Over time, these lakes may drain catastrophically to generate glacier lake outburst floods (GLOFs), which can devastate downstream communities and destroy valuable infrastructure such as roads, bridges, and hydroelectric power facilities. As a result, many risk assessments have been carried out to understand what the triggers of GLOFs might be, in order to better predict their occurrence. One of the main triggers has been assumed to be earthquakes, but this association has not been properly tested. In this paper, we use earthquake and GLOF data from the Peruvian and Bolivian Andes to test this and find that there is little association between earthquakes and GLOFs. We conclude by arguing that focus needs to be on other GLOF triggers, and earthquake activity should be used as a secondary – not primary – indicator in GLOF susceptibility studies. Key Points: Glacier lake outburst floods (GLOFs) are a major risk concern, with earthquakes being commonly considered effective triggers in hazard assessmentsOf 59 earthquakes (1900–2021), the effects of which intersect lakes in the Tropical Andes, only one triggered GLOFsWe suggest that earthquake activity should be used as a secondary – not primary – susceptibility indicator for GLOFs [ABSTRACT FROM AUTHOR]

Climate change may affect sediment fluvial export from high mountain regions, leading to downstream environmental disruptions and direct impacts on human activities. In this paper, three decades (1990–2020) of turbidity measurements, along with climate and hydro‐glaciological variables, were used to investigate the interannual and interdecadal variability in the number of extreme turbidity events (ETE) in the glacierized Maipo River basin, located in the western subtropical Andes. ETE are defined as a sequence of days (most often 1 or 2) during which the daily maximum turbidity was in the 99% quantile of the entire study period. Some of these events compromised the drinking water provision for the city of Santiago, with more than 6 million inhabitants. ETE are more frequent during summer and are mostly associated with melt‐favourable conditions. The number of ETE tends to increase in summers with large glacier ice melt and low snowmelt (outside or over glaciers). Most notable, the mean annual number of ETE exhibits a 6‐fold increase in the last decade compared with the 1990–2010 period. After 2010, ETE also shifted their seasonal maximum from late spring to mid‐summer and their occurrence became strongly coupled with large ice melt rates. We hypothesize that such regime change was caused by an enhanced hydrological connectivity of subglacial sediment pools that increased the sensitivity of the sediment system to glacier melt. The latter is in line with recent research and is consistent with the ongoing glacier retreat due to strong regional warming and drying. Plain Language Summary: Climate change may affect sediment fluvial transport from high mountain regions, leading to environmental disruptions and direct impacts on human activities. In this paper, three decades (1990–2020) of river turbidity measurements to investigate how extreme turbidity events (ETE) have changed in the glacierized Maipo River basin, subtropical Andes. ETE are defined as a sequence of days (most often one or two) during which the turbidity was very high. Some of these events compromised the drinking water provision for the city of Santiago, with more than 6 million inhabitants. ETE are more frequent during summer and are mostly associated with melt‐favourable conditions. Most notable, the mean number of ETE exhibits a sharp increase in the last decade compared with the 1990–2010 period. After 2010, ETE also shifted their seasonal maximum from late spring to mid‐summer and their occurrence became strongly coupled with large ice melt rates. We hypothesize that such regime change was caused by meltwater that has reached subglacial sediments that used to be confined under the glacier ice. The latter is in line with recent research and is consistent with the ongoing glacier retreat as a consequence of intense regional warming and drying. Key Points: The interannual and interdecadal variability in the number of extreme turbidity events are analyzed in a glacierized basin of the AndesMost events are melt‐driven and their number increased by a factor of six during the last decade with respect to the 1990–2010 averageIt is hypothesized that the rise was due to a higher hydraulic connectivity in the subglacial system driven by regional warming and drying [ABSTRACT FROM AUTHOR]

Viscous-flow features in perennially frozen talus/debris called rock glaciers are being systematically inventoried as part of the global climate-related monitoring of mountain permafrost. In order to avoid duplication and confusion, guidelines were developed by the International Permafrost Association to discriminate between the permafrost-related landform "rock glacier" and the glacier-related landform "debris-covered glacier". In two regions covered by detailed field measurements, the corresponding data- and physics-based concepts are tested and shown to be adequate. Key physical aspects which cause the striking morphological and dynamic differences between the two phenomena/landforms concern the following: tight mechanical coupling of the surface material to the frozen rock–ice mixture in the case of rock glaciers, contrasting with essential non-coupling of debris to the glaciers they cover; talus-type advancing fronts of rock glaciers exposing fresh debris material from inside the moving frozen bodies, as opposed to massive surface ice exposed by increasingly rare advancing fronts of debris-covered glaciers; and increasing creep rates and continued advance of rock glaciers as convex landforms with structured surfaces versus predominant slowing down and disintegration of debris-covered glaciers as often concave landforms with primarily chaotic surface structure. Where debris-covered surface ice is or has recently been in contact with thermally controlled subsurface ice in permafrost, complex conditions and interactions can develop morphologies beyond simple either–or-type landform classification. In such cases, the remains of buried surface ice mostly tend to be smaller than the lower size limit of "glaciers" as the term is applied in glacier inventories and to be far thinner than the permafrost in which they are embedded. [ABSTRACT FROM AUTHOR]

The number of studies of Little Ice Age (LIA) glacier fluctuations in southern South America has increased in recent years but is largely biased towards sites in the south Patagonian Andes. In this paper we present a detailed record of length and areal fluctuations of Glaciar Esperanza Norte (GEN) in the north Patagonian Andes of Argentina during the past four centuries. The GEN record was reconstructed through the dendro-geomorphological dating of moraines and the analysis of satellite imagery, aerial photographs and documentary material complemented with extensive field surveys. The maximum LIA extent at GEN was associated with an outer moraine dated to the mid 17th century. At least 19 subsequent readvances or standstills evidenced by morainic ridges were identified inside the most extensive LIA moraine. The dating and spacing of these moraines and the additional information available indicate that the ice front retreated much more rapidly during the 20th century than during earlier centuries. Comparison with the record of LIA fluctuations of Glaciar Fr'ias, an ice mass of similar characteristics located 110 km to the north of GEN, shows a similar pattern of recession over the past 400 yr. Both glacier records have the peak LIA event occurring roughly during the same interval (early-mid 17th century) and show a minor readvance during the 1970s, but there are still a few discrepancies in the dating of some inner moraines. These differences may be due to local, specific factors or associated with the inherent uncertainties in the dating of the moraines. The chronologies of GEN and Fr'ias are among the most detailed currently available in Patagonia, but a larger number of study sites is needed to develop robust, regionally representative glacier chronologies. Detailed glaciological, geomorphological and meteorological data are also needed to understand the glacier-climate relationships in this region and develop reliable paleoclimatic reconstructions. [ABSTRACT FROM AUTHOR]

The aim of this paper is to create a glacial lake inventory for the Cordillera Huayhuash in Peru and to evaluate the susceptibility of lakes to the generation of glacial lake outburst floods (GLOFs). Using high-resolution satellite images, we undertook qualitative and quantitative analysis of lake type, characteristics and distribution, and placed our findings within the context of existing Peru-wide lake inventories. We also mapped and analyzed past GLOFs, revealing a total of 10 GLOFs and 4 ambiguous events, most of which have not been reported before. We found that past GLOFs usually occurred as a result of moraine dam breach during the proglacial stage of lake evolution. Further, we used our lake inventory to evaluate GLOF susceptibility of all lakes larger than 20,000 m2. Of 46 evaluated lakes, only two lakes (Lake Tsacra and Lake W014) are currently susceptible to generating a GLOF, which would most likely be through dam overtopping resulting from a flood originating in smaller lakes located upstream. The future perspectives of lake evolution and implications for GLOF hazard management are discussed in light of the post-Little Ice Age glacier ice loss as well as in the context of extensive related research undertaken in the nearby Cordillera Blanca. [ABSTRACT FROM AUTHOR]

Air pollution in the central zone of Chile is not only a public health concern but also threatens water resources and climate, in connection with the transport and deposition of black carbon (BC) from urban centers onto the glaciers of the Andes. Chemistry-transport simulations reveal a seasonal dichotomy in the flux and latitudinal pattern of BC deposition on glaciers of the central Chilean Andes. The average deposition flux of BC on glaciers between 30 and 37 ∘ S is 4 times larger in winter, affecting mostly low-elevation glaciers, whereas the smaller summertime flux affects glaciers evenly, irrespective of their elevation. The contribution of emissions from the city of Santiago is dominant in summertime with more than 50 % along the Andes but minor in wintertime with less than 20 % even close to the capital city. Transport at larger scales and more local sources likely account for the remaining flux. The superimposition of synoptic-scale circulation and local mountain-valley circulation along the Andes drives the differences between summertime and wintertime deposition fluxes and generates a greater meteorological export potential during summer months. Future emissions and climate projections suggest that under the RCP8.5 scenario the gap between summertime and wintertime BC export and deposition flux could decrease, thereby pointing to summertime emission control gaining relevance. The chemistry-transport modeling approach for BC deposition on the Andes sheds light on the importance of the often disregarded summertime emissions on the radiative balance of its glaciers, particularly in the vicinity of Santiago. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of the evolution of the glaciers on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behaviour was observed over the whole period, with two periods of strong mass loss, 1956–1964 (-0.72 m w.e. yr -1) and 1979–1997 (-0.82 m w.e. yr -1), and two periods with slight mass loss, 1965–1978 (0.10 m w.e. yr -1) and 1998–2016 (-0.26 m w.e. yr -1). There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g. maximum and median altitude and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5 and 16) which have been undergoing accelerated disintegration since the 1990s and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers have reacted in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet–dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm–cold conditions observed in the Pacific Ocean represented by the Southern Oscillation index. [ABSTRACT FROM AUTHOR]

The Last Glacial Termination (T1) featured major changes in global circulation systems that led to a shift from glacial to interglacial climate. While polar ice cores attest to an antiphased thermal pattern at millennial timescales, recent well-dated moraine records from both hemispheres suggest in-phase fluctuations in glaciers through T1, which is inconsistent with the bipolar see-saw paradigm. Here, we present a glacier chronology based on 30 new 10Be surface exposure ages from well-preserved moraines in the Lago Palena/General Vintter basin in northern Patagonia (~ 44°S). We find that the main glacier lobe underwent profound retreat after 19.7 ± 0.7 ka. This recessional trend led to the individualization of the Cerro Riñón glacier by ~ 16.3 ka, which underwent minor readvances at 15.9 ± 0.5 ka during Heinrich Stadial 1, during the Antarctic Cold Reversal with successive maxima at 13.5 ± 0.4, 13.1 ± 0.4, and 13.1 ± 0.5 ka, and a minor culmination at 12.5 ± 0.4 ka during Younger Dryas time. We conclude that fluctuations of Patagonian glaciers during T1 were controlled primarily by climate anomalies brought by shifts in the Southern Westerly Winds (SWW) locus. We posit that the global covariation of mountain glaciers during T1 was linked to variations in atmospheric CO2 (atmCO2) promoted by the interplay of the SWW-Southern Ocean system at millennial timescales. [ABSTRACT FROM AUTHOR]

Glaciers in the Andes of Chile seem to be shrinking and possibly loosing mass, but the number and types of studies conducted, constrained mainly by data availability, are not sufficient to provide a synopsis of glacier changes for the past or future or explain in an explicit way causes of the observed changes. In this paper, we provide a systematic review of changes in glaciers for the entire country, followed by a discussion of the studies that have provided evidence of such changes. We identify a missing type of work in distributed, physically-oriented modelling studies that are needed to bridge the gap between the numerous remote sensing studies and the specific, point scale works focused on process understanding. We use an advanced mass balance model applied to one of the best monitored glaciers in the region to investigate four main research issues that should be addressed in modelling studies for a sound assessment of glacier changes: 1) the use of physically-based models of glacier ablation (energy balance models) versus more empirical models (enhanced temperature index approaches); 2) the importance of the correct extrapolation of air temperature forcing on glaciers and in high elevation areas and the large uncertainty in model outputs associated with it; 3) the role played by snow gravitational redistribution; and 4) the uncertainty associated with future climate scenarios. We quantify differences in model outputs associated with each of these choices, and conclude with suggestions for future work directions. [ABSTRACT FROM AUTHOR]

The Younger Dryas stadial, a cold event spanning 12,800 to 11,500 years ago, during the last deglaciation, is thought to coincide with the last major glacial re-advance in the tropical Andes. This interpretation relies mainly on cosmic-ray exposure dating of glacial deposits. Recent studies, however, have established new production rates for cosmogenic 10Be and 3He, which make it necessary to update all chronologies in this region and revise our understanding of cryospheric responses to climate variability. Here we present a new 10Be moraine chronology in Colombia showing that glaciers in the northern tropical Andes expanded to a larger extent during the Antarctic cold reversal (14,500 to 12,900 years ago) than during the Younger Dryas. On the basis of a homogenized chronology of all 10Be and 3He moraine ages across the tropical Andes, we show that this behaviour was common to the northern and southern tropical Andes. Transient simulations with a coupled global climate model suggest that the common glacier behaviour was the result of Atlantic meridional overturning circulation variability superimposed on a deglacial increase in the atmospheric carbon dioxide concentration. During the Antarctic cold reversal, glaciers advanced primarily in response to cold sea surface temperatures over much of the Southern Hemisphere. During the Younger Dryas, however, northern tropical Andes glaciers retreated owing to abrupt regional warming in response to reduced precipitation and land-surface feedbacks triggered by a weakened Atlantic meridional overturning circulation. Conversely, glacier retreat during the Younger Dryas in the southern tropical Andes occurred as a result of progressive warming, probably influenced by an increase in atmospheric carbon dioxide. Considered with evidence from mid-latitude Andean glaciers, our results argue for a common glacier response to cold conditions in the Antarctic cold reversal exceeding that of the Younger Dryas. [ABSTRACT FROM AUTHOR]

Landslides in deglaciated and deglaciating mountains represent a major hazard, but their distribution at the spatial scale of entire mountain belts has rarely been studied. Traditional models of landslide distribution assume that landslides are concentrated in the steepest, wettest, and most tectonically active parts of the orogens, where glaciers reached their greatest thickness. However, based on mapping large landslides (> 0.9 km2) over an unprecedentedly large area of Southern Patagonia (~ 305,000 km2), we show that the distribution of landslides can have the opposite trend. We show that the largest landslides within the limits of the former Patagonian Ice Sheet (PIS) cluster along its eastern margins occupying lower, tectonically less active, and arid part of the Patagonian Andes. In contrast to the heavily glaciated, highest elevations of the mountain range, the peripheral regions have been glaciated only episodically, leaving a larger volume of unstable sedimentary and volcanic rocks that are subject to ongoing slope instability. [ABSTRACT FROM AUTHOR]

Based on new and published cosmic-ray exposure chronologies, we show that glacier extent in the tropical Andes and the north Atlantic regions (TANAR) varied in-phase on millennial timescales during the Holocene, distinct from other regions. Glaciers experienced an early Holocene maximum extent, followed by a strong mid-Holocene retreat and a re-advance in the late Holocene. We further explore the potential forcing of TANAR glacier variations using transient climate simulations. Since the Atlantic Meridional Overturning Circulation (AMOC) evolution is poorly represented in these transient simulations, we develop a semi-empirical model to estimate the "AMOC-corrected" temperature and precipitation footprint at regional scales. We show that variations in the AMOC strength during the Holocene are consistent with the observed glacier changes. Our findings highlight the need to better constrain past AMOC behavior, as it may be an important driver of TANAR glacier variations during the Holocene, superimposed on other forcing mechanisms. Glaciers showed a similar evolution in Greenland, Europe, the US and the tropical Andes during the Holocene. The authors propose the Atlantic Meridional Ocean Overturning Circulation as a key driver of this trend. [ABSTRACT FROM AUTHOR]

One way of deducing vertical shifts in the altitudinal distribution of Colombian high-altitude páramo environments is by inferring fluctuations in the height of the local freezing level. In our research, we are implementing two complementary approaches to reconstruct Late Pleistocene to Holocene changes in the freezing level height (FLH) in two of the most extensively glacier-covered areas of the northern Andes. We combined remote sensing and field-based geomorphological mapping with time-series reconstruction of changes in the altitude of the 0°C isotherm. Changes in the FLH were based on already-published ∼30 kyr paleo-reconstructions of sea surface temperatures (SSTs) of the eastern tropical Pacific and the western tropical Atlantic, as well as on reconstructed long-term sea level changes and empirical orthogonal functions of present-day (historical) Indo-Pacific and tropical Atlantic SST anomalies. We also analyzed the probability distribution of air-sea temperature differences and the spatial distribution of grid points with SSTs above the minimum threshold necessary to initiate deep convection. We considered available historical near-surface and free air temperature data of ERA-Interim reanalysis products, General Circulation Model (GCM) simulations, weather stations, and (deployed by our group) digital sensors, to assess the normal Environmental Lapse Rates (ELRs) at the regional to local scale. The combined maps of glacial landforms and our reconstructed FLHs provided us with a well-founded inference of potential past glacier advances, narrowing down the coarse resolution of ice margins suggested by previous research efforts. The extent of the areas with temperatures below the freezing point suggested here for the summits of our main study site exceeds in magnitude the corresponding glacier icecaps and front advances proposed by previous studies. Conversely, our average lowest altitudes of the FLH for our comparative site are consistently above the main glacier-front advances previously suggested. Our results indicate that, compared to the maximum upward changes that likely took place over the past ca. observed (present-day) upward shifts of the FLH have occurred at a rate that significantly surpasses our inferred rates. Our study helps fill the gaps in understanding past climatic changes and present trends in the region of interest and provides some insights into analyzing the signals of natural and anthropogenic climate change. [ABSTRACT FROM AUTHOR]

Many mountain regions around the world are exposed to enhanced warming when compared to their surroundings, threatening key environmental services provided by mountains. Here we investigate this effect, known as elevation-dependent warming (EDW), in the Andes of Ecuador, using observations and simulations with the Weather Research and Forecasting (WRF) Model. EDW is discernible in observations of mean and maximum temperature in the Andes of Ecuador, but large uncertainties remain due to considerable data gaps in both space and time. WRF simulations of present-day (1986–2005) and future climate (RCP4.5 and RCP8.5 for 2041–60) reveal a very distinct EDW signal, with different rates of warming on the eastern and western slopes. This EDW effect is the combined result of multiple feedback mechanisms that operate on different spatial scales. Enhanced upper-tropospheric warming projects onto surface temperature on both sides of the Andes. In addition, changes in the zonal mean midtropospheric circulation lead to enhanced subsidence and warming over the western slopes at high elevation. The increased subsidence also induces drying, reduces cloudiness, and results in enhanced net surface radiation receipts, further contributing to stronger warming. Finally, the highest elevations are also affected by the snow-albedo feedback, due to significant reductions in snow cover by the middle of the twenty-first century. While these feedbacks are more pronounced in the high-emission scenario RCP8.5, our results indicate that high elevations in Ecuador will continue to warm at enhanced rates in the twenty-first century, regardless of emission scenario. Significance Statement: Mountains are often projected to experience stronger warming than their surrounding lowlands going forward, a phenomenon known as elevation-dependent warming (EDW), which can threaten high-altitude ecosystems and lead to accelerated glacier retreat. We investigate the mechanisms associated with EDW in the Andes of Ecuador using both observations and model simulations for the present and the future. A combination of factors amplify warming at mountain tops, including a stronger warming high in the atmosphere, reduced cloudiness, and a reduction of snow and ice at high elevations. The latter two factors also favor enhanced absorption of sunlight, which promotes warming. The degree to which this warming is enhanced at high elevations in the future depends on the greenhouse gas emission pathway. [ABSTRACT FROM AUTHOR]

Abstract: This paper documents the occurrence of the Little Ice Age (LIA) in the El Azufre and El Peñón glaciers at 35°S and in the Las Choicas and Las Damas glaciers at 34°55′S in the headwaters of the Rio Grande basin in the Central Andes of Argentina. Moraine morphology, stratigraphic relationships, radiocarbon ages obtained from peat on these glacial deposits and the proximity to the active glaciers enabled us to reconstruct the LIA advance in this area. The LIA maximum advance occurred between cal. yr 1550 and 1720 AD, and a readvance occurred around cal. yr 1830 AD. In addition, glacier fluctuations of the Las Vacas and Güssfeltd glaciers (33°S) and El Peñón and El Azufre glaciers were documented from the end of the 19th century to the present based on historical and aerial photographs, and satellite images. The glaciers showed a marked retreat during 1894–2007. Minor readvances occurred in the 1980s and 1990s, which could be related with strong warm ENSO events during these decades. Our results are consistent with observations made by other authors in the region. [Copyright &y& Elsevier]

Abstract: This paper presents an updated, extensive review of glacier fluctuations during the past 1000years in the extratropical Andes of South America between ca. 17° and 55°S. Given the variety of environmental conditions and evidence available for glacier fluctuations across this wide latitudinal range, regional accounts are given for the Desert Andes (∼17°–31°S), the Andes of central Chile and Argentina (31°–36°S), and the North (36°–45°S) and South (45°–55°S) Patagonian Andes. The techniques, dating limitations, and interpretations of the glacier records along this transect are also discussed. Information on glacier fluctuations in the Desert Andes is limited to the 20th century. Documentation on past glacier variations is more abundant in the Central Chilean-Argentinean Andes, but the number of chronologies dealing with glacier fluctuations prior to the 1900s is also limited. Most records indicate that glaciers were generally more extensive prior to the 20th century, with dates of maximum expansion ranging from the 16th to the 19th centuries. The number and extent of glaciers increase significantly in the Patagonian region, where the evidence available for dating glacier variations during the past centuries is more abundant and the dating control for glacier events is generally better than in the northern parts of the study area. For some Patagonian glaciers, maximum Little Ice Age (LIA) or post-LIA advances have been precisely dated by dendro-geomorphological determinations or in situ measurements. However, for most sites, the evidence available is still preliminary and there is considerable variability in the extent and timing of events related to the maximum LIA expansion identified in most areas between the 16th and 19th centuries. Evidence is starting to appear at a growing number of sites for glacier advances during the first half of the past millennium. These events were generally less extensive than the LIA maximum pulses. Despite the occurrence of several post-LIA readvances over the past 100–110years, most areas in the Andes of extratropical South America have experienced a general pattern of glacier recession and significant ice mass losses. The differences in the glacier histories observed at local and regional scales probably reflect the inherent limitations associated with the glacier records and/or the dating techniques used in each case together with the varying dominance of precipitation, temperature and other climatic and non-climatic factors on glacier mass balance and glacier dynamics. These differences indicate that the late Holocene glacier history of southern South America is more complex than commonly assumed. The evidence discussed in this study highlights not only the immense potential for glaciological studies of this region but also a significant need for an increased number of detailed, well-dated records of glacier fluctuations. [Copyright &y& Elsevier]

Glacier recession in response to climate warming has resulted in an increase in the size and number of glacial lakes. Glacial lakes are an important focus for research as they impact water resources, glacier mass balance, and some produce catastrophic glacial lake outburst floods (GLOFs). Glaciers in Peru have retreated and thinned in recent decades, prompting the need for monitoring of ice- and water-bodies across the cordilleras. These monitoring efforts have been greatly facilitated by the availability of satellite imagery. However, knowledge gaps remain, particularly in relation to the formation, temporal evolution, and catastrophic drainage of glacial lakes. In this paper we address this gap by producing the most current and detailed glacial lake inventory in Peru and provide a set of reproducible methods that can be applied consistently for different time periods, and for other mountainous regions. The new lake inventory presented includes a total of 4557 glacial lakes covering a total area of 328.85 km2. In addition to detailing lake distribution and extent, the inventory includes other metrics, such as dam type and volume, which are important for GLOF hazard assessments. Analysis of these metrics showed that the majority of glacial lakes are detached from current glaciers (97%) and are classified as either embedded (i.e. bedrock dammed; ~64% of all lakes) or (moraine) dammed (~28% of all lakes) lakes. We also found that lake size varies with dam type; with dammed lakes tending to have larger areas than embedded lakes. The inventory presented provides an unparalleled view of the current state of glacial lakes in Peru and represents an important first step towards (1) improved understanding of glacial lakes and their topographic and morphological characteristics and (2) assessing risk associated with GLOFs. • We present a new contemporary and comprehensive lake inventory for the Peruvian Cordilleras • We provide a set of inventorying methods to facilitate replicability in other locations, globally • We record and analyse a number of important lake metrics for understanding GLOF hazards • We estimate lake volume in all glaciated cordilleras and compare these with other studies [ABSTRACT FROM AUTHOR]

Glaciers and ice caps are thinning and retreating along the entire Andes ridge, and drivers of this mass loss vary between the different climate zones. The southern part of the Andes (Wet Andes) has the highest abundance of glaciers in number and size, and a proper understanding of ice dynamics is important to assess their evolution. In this contribution, we apply the ice-sheet model SICOPOLIS (SImulation COde for POLythermal Ice Sheets) to the Mocho-Choshuenco ice cap in the Chilean Lake District (40 ∘ S, 72 ∘ W; Wet Andes) to reproduce its current state and to project its evolution until the end of the 21st century under different global warming scenarios. First, we create a model spin-up using observed surface mass balance data on the south-eastern catchment, extrapolating them to the whole ice cap using an aspect-dependent parameterization. This spin-up is able to reproduce the most important present-day glacier features. Based on the spin-up, we then run the model 80 years into the future, forced by projected surface temperature anomalies from different global climate models under different radiative pathway scenarios to obtain estimates of the ice cap's state by the end of the 21st century. The mean projected ice volume losses are 56±16 % (RCP2.6), 81±6 % (RCP4.5), and 97±2 % (RCP8.5) with respect to the ice volume estimated by radio-echo sounding data from 2013. We estimate the uncertainty of our projections based on the spread of the results when forcing with different global climate models and on the uncertainty associated with the variation of the equilibrium line altitude with temperature change. Considering our results, we project a considerable deglaciation of the Chilean Lake District by the end of the 21st century. [ABSTRACT FROM AUTHOR]

Resolving the history of vegetation, fire, and glaciation on the eastern slope of the central Patagonian Andes (44°-49°S) since the Last Glacial Termination (T1) has proved difficult. This is due to the steep environmental gradients, vegetation heterogeneity, and scarcity of dated glacial deposits and geomorphic features. Unsurprisingly, published records show important heterogeneities which limit our understanding of the timing and magnitude of climate and vegetation changes, and their driving mechanisms since T1. In this paper, we describe sediment cores from small closed-basin lakes located in the deciduous Nothofagus forest zone near Coyhaique, Chile. Our results indicate that the Coyhaique glacier lobe abandoned its final Last Glacial Maximum position just before ~17.9 cal kyr BP and underwent a step-wise recession that included a halt/readvance that culminated at ~16.8 cal kyr BP, contemporaneous with the formation of an ice-dammed proglacial lake in the Coyhaique/Balmaceda sector. This glacial lake stood at its highest level between ~17.9–17.2 cal kyr BP (<726 and > 650 m.a.s.l.), lowered between ~17.2–16.2 cal kyr BP (<650 and > 570 m.a.s.l.), and disappeared thereafter. Herbs and shrubs, currently dominant in high Andean and Patagonian steppe environments, colonized the ice-free terrains distal to the glacier margins and proglacial lakes under cold and dry conditions. This was followed by a steady increase in Nothofagus between ~16.6–14.8 cal kyr BP that led to the establishment of forests starting at ~14.8 cal kyr BP. The Holocene started with a sudden increase in Nothofagus and disappearance of conifers in the context of increase fire activity between ~11.7–9.4 cal kyr BP. Closed-canopy Nothofagus forests persisted virtually unaltered from ~9.4 cal kyr BP to the present day, despite frequent explosive volcanism and millennial-scale variations in fire regimes, attesting to their extraordinary postglacial resilience which contrasts with their behavior during T1. Recent large-scale deforestation by fire, livestock grazing, and the spread of non-native invasive plant species drove the fastest and largest-magnitude shifts seen during the last ~16,500 years. • Glacial retreat began at ~17.9 ka and followed a stepwise pattern until ~16.2 ka. • Arboreal Pollen rose at ~16.6 ka driven by stronger Southern Westerly Winds (SWW). • Rainforest conifers peaked between ~14.8–11.7 ka suggesting maximum SWW influence. • Fires and disappearance of conifers suggest weak SWW between ~11.7–9.4 ka. • Extraordinarily resilient Nothofagus forests have persisted since ~9.4 ka. [ABSTRACT FROM AUTHOR]

Global patterns of sea-level change – often termed "sea-level fingerprints" – associated with future changes in ice/water mass re-distribution are a key component in generating regional sea-level projections. Calculation of these fingerprints is commonly based on the assumption that the isostatic response of the Earth is dominantly elastic on century timescales. While this assumption is accurate for regions underlain by mantle material with viscosity close to that of global average estimates, recent work focusing on the West Antarctic region has shown that this assumption can lead to significant error where the viscosity is significantly lower than typical global average values. Here, we test this assumption for fingerprints associated with glaciers and ice caps. We compare output from a (1D) elastic Earth model to that of a 3D viscoelastic model that includes low-viscosity mantle in three glaciated regions: Alaska, southwestern Canada, and the southern Andes (Randolph Glacier Inventory (RGI) regions 1, 2, and 17, respectively). This comparison indicates that the error incurred by ignoring the non-elastic response is of the order of 1 mm in most areas (or about 1 % of the barystatic signal) over the 21st century with values reaching the centimetre level in glaciated regions. However, in glaciated regions underlain by low-viscosity mantle, the non-elastic deformation can result in relative sea-level changes with magnitudes of up to several tens of centimetres (or several times the barystatic value). The magnitude and spatial pattern of this non-elastic signal is sensitive to variations in both the projected ice history and regional viscosity structure, indicating the need for loading models with high spatial resolution and improved constraints on regional Earth viscosity structure to accurately simulate sea-level fingerprints in these regions. The anomalously low mantle viscosity in these regions also amplifies the glacial isostatic adjustment signal associated with glacier changes during the 20th century, causing it to be an important (and even dominant) contributor to the modelled relative sea-level changes over the 21st century. [ABSTRACT FROM AUTHOR]

Glaciers and the periglacial environment in Argentina have been protected by the Law since 2010. This legislation required the development of the first National Glacier Inventory (NGI), which was officially presented in May 2018 and based on satellite images spanning between 2004 and 2016. Here, we present the methods and results of the NGI, summarize the glaciers' morphological and spatial characteristics, and compare our results to previous regional and global inventories. The NGI reveals an impressive variety of ice masses including rock glaciers, permanent snowfields, mountain and valley glaciers with varying amounts of debris-cover and large outlet glaciers. The Argentinean Andes contain 16 078 ice masses covering an area of 5769 km2 between 200 and 6900 m a.s.l. Comparison of the combined national inventories of Argentina and Chile (~30 000 glaciers and 28 400 km2) with the Randolph Glacier Inventory 6.0 for the Southern Andes (~16 000 glaciers and 29 400 km2), shows that there are large differences in extent and number of glaciers in some sub-regions. The NGI represents an improvement for a better understanding of Argentina's freshwater reservoirs and provides detailed information for the preservation and study of ice masses along 4000 km of the Southern Andes. [ABSTRACT FROM AUTHOR]

The mountain cryosphere is one of the strongest affected systems by climate change. Glacier shrinkage leads to cascading impacts, including changes in river flow regimes, availability of water resources for downstream populations and economy, changes in the occurrence and severity of natural hazards, and cultural changes associated with landscape character and identity. In this study, we analyze impacts of mountain cryosphere change through a lens of Loss and Damage (L&D), a mechanism of international climate policy that tries to evaluate and reduce negative consequences of climate change for societies. We analyze the effects of climate change on glacier change, glacier lake formation and growth, hydrological regimes, and associated impacts on human societies in the Cordillera Blanca in the Peruvian Andes, now and under future scenarios. We use various methods such as literature review, glacial lake outburst flood, and hydrologic modeling to examine three major dimensions of cryospheric change and associated human impacts: (i) ice loss; (ii) glacial hazards; and (iii) variability of water availability. We identify the damage and losses in terms of the number of people affected by glacial hazards, monetized agricultural crop loss due to water loss, and non-economic values local people attribute to glacier loss. We find that different levels of warming have important negative but differentiated effects on natural and human systems. We also contend that the extent of loss and damage will largely be determined by governance and adaptation decisions such as water resource management and disaster risk management. We suggest that these lines of evidence are more explicitly taken into account in L&D policies. [ABSTRACT FROM AUTHOR]

Evidence of observed negative impacts on natural and human systems from anthropogenic climate change is increasing. However, human systems in particular are dynamic and influenced by multiple drivers and hence identifying an anthropogenic climate signal is challenging. Here we analyze the case of lake Palcacocha in the Andes of Peru, which offers a representative model for other glacier lakes and related risks around the world because it features a dynamic evolution of flood risk driven by physical and socioeconomic factors and processes. Furthermore, it is the object of a prominent climate litigation case, wherein a local Peruvian citizen sued a large German energy producer over risk of flooding from lake Palcacocha. Adopting a conceptual model of cascading impacts and multiple drivers of risk, we first study climatic and other geophysical drivers of flood risk. We find that an anthropogenic signal from flood risk to greenhouse gas emissions is traceable. In parallel, flood risk has been strongly shaped (and increased) by interacting socioeconomic, institutional and cultural processes over the past few decades. The case raises important questions about the differentiation of responsibilities relating to flood risk of both global and local agents, which are, however, difficult to address in cases like Palcacocha, where we reveal a complex network of interlinked global, national and local drivers. Following from this, we outline a normative framework with a differentiated perspective on responsibility, implying that global emitters commit to support strengthening capacities in affected regions and localities and that local institutions and societies engage in local risk reduction measures and policies in collaboration with and driven by local communities. [ABSTRACT FROM AUTHOR]

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Reconstructing the evolution of the glacial landscape of the semi-arid Andes (32°–34° S) during phases of Holocene deglaciation is key to understand the responses of the cryosphere during warmer periods such as the current one. Despite having geomorphological records with good degrees of preservation, few studies have addressed the changes of the Andes during the glacial-paraglacial transition. In this paper, we investigate and compare geomorphological mappings of four glacial sub-basins of the central Andes of Chile: Juncal Norte (32° S, glacier terminus at ~ 3000 m asl.), Loma Larga (33° S, terminus at ~ 3000 m asl.), Nieves Negras (33° S, terminus at ~ 3000 m asl.), and Universidad (34° S, terminus at ~ 2500 m asl.). The ablation zones of Loma Larga and Nieves Negras glaciers have a mantle of debris, which suggests a process of ablation in situ rather than retreat of the glacier tongue. Both glaciers have a morphology of internal collapse in their debris-covered section. On the other hand, Juncal Norte and Universidad glaciers both have lateral moraines with ice cores, where the differential ablation has triggered backwasting and downwasting processes. The presence of ice-cored lateral moraines indicates greater activity of processes in the lateral sections. The Universidad glacier is characterized by two branches feeding the glacier tongue which shows a prominent medial moraine.For the first time in this part of the Andes, we used 36Cl terrestrial cosmogenic nuclides (TCN) for dating deglaciation geomorphology. We complement our 36Cl data with 14C ages that suggest that glaciers advanced before ~2500 and then before ~850/1000 years BP.The combination of the geomorphology and the geochronology in the different proglacial areas allows the analysis of the deglaciation history and related processes. Identifying how ablation occurs in semi-arid mountain environments is important to assess the behaviour of ice under changing climatic conditions and its preservation under a cover of debris. One of the characteristics and challenges of the deglaciation in the semi-arid Andes is the high production of debris in the ablation zones. [ABSTRACT FROM AUTHOR]

Glaciers in tropical regions are very sensitive to climatic variations and thus strongly affected by climate change. The majority of the tropical glaciers worldwide are located in the Peruvian Andes, which have shown significant ice loss in the last century. Here, we present the first multi-temporal, region-wide survey of geodetic mass balances and glacier area fluctuations throughout Peru covering the period 2000–2016. Glacier extents are derived from Landsat imagery by performing automatic glacier delineation based on a combination of the NDSI and band ratio method and final manual inspection and correction. The mapping of debris-covered glacier extents is supported by synthetic aperture radar (SAR) coherence information. A total glacier area loss of -548.5±65.7 km 2 (-29 %, -34.3 km 2 a -1) is obtained for the study period. Using interferometric satellite SAR acquisitions, bi-temporal geodetic mass balances are derived. An average specific mass balance of -296±41 kg m -2 a -1 is found throughout Peru for the period 2000–2016. However, there are strong regional and temporal differences in the mass budgets ranging from 45±97 to -752±452 kg m -2 a -1. The ice loss increased towards the end of the observation period. Between 2013 and 2016, a retreat of the glacierized area of -203.8±65.7 km 2 (-16 %, -101.9 km 2 a -1) is mapped and the average mass budget amounts to -660±178 kg m -2 a -1. The glacier changes revealed can be attributed to changes in the climatic settings in the study region, derived from ERA-Interim reanalysis data and the Oceanic Nino Index. The intense El Niño activities in 2015/16 are most likely the trigger for the increased change rates in the time interval 2013–2016. Our observations provide fundamental information on the current dramatic glacier changes for local authorities and for the calibration and validation of glacier change projections. [ABSTRACT FROM AUTHOR]

Climate change and its effects are taking more importance nowadays; and glaciers are one of the most affected ecosystems by that, considering that the energy of Earth's surface and its temperature may be directly related to glacier temporal changes. Then, the comprehension of glaciers behaviour, by its retreating or melting critical conditions, can be achieved by the analysis of Remote Sensing data, but considering the unprecedented volumes of information currently provided by satellites sensors, we can refer to this analysis as a big data problem. Machine learning techniques have the potential to improve the analysis of this type of data; however, most current machine learning algorithms are unable to properly process such huge volumes of data. In the attempt to overcome the computational limitations related to Remote Sensing Big Data analysis, we implemented the K-Means and Expectation Maximization algorithms, as distributed clustering solutions, exploiting the capabilities of cloud computing infrastructure for processing very large datasets. The solution was developed over the InterCloud Data Mining Package, which is a suite of distributed classification methods, previously employed in hyperspectral image analysis. In this work we extended the functionalities of that package, by making it able to process multispectral images using the aforementioned clustering algorithms. To validate our proposal, we analysed the Ausangate glacier, located on the Andes Mountains, in Peru, by mapping the changes in such environment through a multi-temporal Remote Sensing analysis. Our results and conclusions are focused on the thematic accuracy and the computational performance achieved by our proposed solution. Thematic accuracy was assessed by comparing the automatically detected glacier areas by the clustering approaches against the manually selected ground truth data. We compared the computational load involved in executing the clustering processes sequentially and in a distributed fashion, using a local mode and cluster configuration over a cloud computing infrastructure. [ABSTRACT FROM AUTHOR]

Recent decades, particularly since the late 1970s, have witnessed a rapid retreat of glaciers in the tropical Andes. We compiled the changes in glacier surfaces along the eastern cordilleras of the tropical Andes of Peru and Bolivia since the early 1980s from the literature. Water levels from two Brazilian river basins in the Amazon basin (one (Madeira River) glacially fed by meltwater from the Andes and the other (Envira River) non‐glacially fed), were analysed for a 30‐year period between 1985−2014. Furthermore, precipitation data near these two basins were also analysed in order to understand the differential contributions of glacier melting and rainfall. Variations in the water levels from the glacially fed Madeira River showed that some years were associated with higher water levels even when the precipitation remained low during the corresponding season (May‐October). This observation was common when El Niño events occurred during the positive phase of Pacific Decadal Oscillation (PDO). Water levels in glacier‐fed Madeira River were slightly higher during the periods where El Niño and warm PDO co‐occurred. On the other hand, water levels in the Envira River were precipitation dependent; water levels were higher when the rainfall was high. [ABSTRACT FROM AUTHOR]

Cushion plant dominated peatlands are key ecosystems in tropical alpine regions of the Andes in South America. The cushion plants have formed peat bodies over thousands of years that fill many valley bottoms, and the forage produced by the plants is critical for native and nonnative domesticated mammals. The sources and flow paths of water supporting these peatlands remain largely unknown. Some studies have suggested that glacier meltwater streams support some peatlands, and that the ongoing loss of glaciers and their meltwaters could lead to the loss or diminishment of peatlands. We analysed the hydrologic regime of 10 peatlands in four mountain regions of Bolivia and Peru using groundwater monitoring. Groundwater levels in peatlands were relatively stable and within 20 cm of the ground surface during the rainy season, and many sites had water tables 40–90 cm below the ground surface in the dry season. Topographic and groundwater elevations in the peatlands demonstrated that the water source of all 10 peatlands was hillslope groundwater flowing from lateral moraines, talus, colluvium, or bedrock aquifers into the peatlands. There was little to no input from streams, whether derived from glacier melt or other sources, and glacier melt could not have recharged the hillslope aquifers supporting peatlands. We measured the stable water isotopes in water samples taken during different seasons, distributed throughout the catchments, and the values are consistent with this interpretation. Our findings indicate that peatlands in the study region are recharged by hillslope groundwater discharge rather than stream water and may not be as vulnerable to glacial decline as other studies have indicated. However, both glaciers and peatlands are susceptible to changing thermal and precipitation regimes that could affect the persistence of peatlands. [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]

Andean tropical glaciers have shown a clear shrinkage throughout the last few decades. However, it is unclear how this general retreat is associated with variations in rainfall patterns in the Amazon basin. To investigate this question, we compared the annual net accumulation variations in the Bolivian Cordillera Real (Andes), which is derived from an ice core from the Nevado Illimani (16° 37' S, 67° 46' W), covering the period 1960--1999 using the Amazonian Rainfall Index, Northern Atlantic Index (TNA), Multivariate ENSO Index (MEI), and Pacific Decadal Oscillation (PDO). The accumulation rate at the Nevado Illimani ice core decreased by almost 25% after 1980, from 1.02 w.eq. a-1 (water equivalent per year) in the 1961-1981 period to 0.76 w.eq. a-1 in the 1981-1999 period. The Northern Amazonian Rainfall (NAR) index best reflects changes in accumulation rates in the Bolivian ice core. Our proposal is based on two observations: (1) This area shows reduced rainfall associated with a more frequent and intense El Niño (during the positive phase of the MEI). The opposite (more rain) is true during La Niña phases. (2) Comparisons of the ice core record and NAR, PDO, and MEI indexes showed similar trends for the early 1980s, represented by a decrease in the accumulation rates and its standard deviations, probably indicating the same causality. The general changes observed by early 1980s coincided with the beginning of a PDO warm phase. This was followed by an increase in the Amazonian and tropical Andean precipitation from 1999, coinciding with a new PDO phase. However, this increase did not result in an expansion of the Zongo Glacier area. [ABSTRACT FROM AUTHOR]

While the tropical Andes of Venezuela, Colombia, Ecuador, Peru, Bolivia, northern Chile, and northern Argentina represent more than 95% of all tropical glaciers globally, they are relatively sparsely studied in general, and particularly by using remote-sensing approaches. However, studies from the 1930s used terrestrial imaging, and aerial photographs are available from the 1950s on. In this article, we review the literature on remote sensing of the glaciers in the tropical Andes, divided into the four climatic subregions: inner tropics, dry outer tropics, northern wet outer tropics, and southern wet outer tropics. The majority of studies used optical remote sensing, particularly Landsat and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imagery, although shadows produced by steep terrain and often dense cloud cover - within the Intertropical Convergence Zone (ITCZ) of the inner tropics - are challenges to data analyses. Microwave and lidar remote sensing have been successfully employed in some studies. The vast majority of glacier monitoring studies documented glacier recessions throughout the tropical Andes since the 1950s; most results are available for the Peruvian Andes, particularly the Cordillera Balance. Recent field tests explored the use of unmanned aerial systems (UAS) and lidar in glacier research; preliminary results are promising and have the potential to lead into new research directions. [ABSTRACT FROM AUTHOR]

The first satellite-derived inventory of glaciers and rock glaciers in Chile, created from Landsat TM/ETM+ images spanning between 2000 and 2003 using a semi-automated procedure, is presented in a single standardized format. Large glacierized areas in the Altiplano, Palena Province and the periphery of the Patagonian icefields are inventoried. The Chilean glacierized area is 23 708 ± 1185 km2, including ~3200 km2 of both debris-covered glaciers and rock glaciers. Glacier distribution varies as a result of climatic gradients with latitude and elevation, with 0.8% occurring in the Desert Andes (17°30′–32° S); 3.6% in the Central Andes (32–36° S), 6.2% in the Lakes District and Palena Province (36–46° S), and 89.3% in Patagonia and Tierra del Fuego (46–56° S). Glacier outlines, across all glacierized regions and size classes, updated to 2015 using Landsat 8 images for 98 complexes indicate a decline in areal extent affecting mostly clean-ice glaciers (−92.3 ± 4.6 km2), whereas debris-covered glaciers and rock glaciers in the Desert and Central Andes appear nearly unchanged in their extent. Glacier attributes estimated from this new inventory provide valuable insights into spatial patterns of glacier shrinkage for assessing future glacier changes in response to climate change. [ABSTRACT FROM AUTHOR]

Diatoms in ice cores have been used to infer regional and global climatic events. These archives offer high-resolution records of past climate events, often providing annual resolution of environmental variability during the Late Holocene. Recently, the first low-latitude tropical diatoms were described from the Quelccaya Summit Dome. Here, we document diatoms observed in ice cores from Quelccaya, spanning AD 1300 to 1815, along with those from two additional glaciers (Coropuna, and Sajama glaciers) in the tropical Andes, spanning AD 1764 to 1814. Diatom assemblages recovered from these three sites were rare, but differ in abundance and species composition through time. Assemblages are characterized by cosmopolitan and aerophilic species, mostly pennate diatoms. There were 44 taxa in all, withPinnulariacf.borealisEhrenberg being the most common species encountered in the samples. Eleven taxa were found at all three sites. Both Coropuna and Sajama had taxa that were unique to these locations, whereas Quelccaya had no unique taxa. Due to the rarity of diatoms and the cosmopolitan nature of the dominant species, it is not possible to determine their origin, limiting their utility in paleoclimate reconstructions. [ABSTRACT FROM AUTHOR]

Mountain ranges are the world's natural water towers and provide water resources for millions of people. However, their hydrological balance and possible future changes in river flow remain poorly understood because of high meteorological variability, physical inaccessibility, and the complex interplay between climate, cryosphere, and hydrological processes. Here, we use a state-of-the art glacio-hydrological model informed by data from high-altitude observations and the latest climate change scenarios to quantify the climate change impact on water resources of two contrasting catchments vulnerable to changes in the cryosphere. The two study catchments are located in the Central Andes of Chile and in the Nepalese Himalaya in close vicinity of densely populated areas. Although both sites reveal a strong decrease in glacier area, they show a remarkably different hydrological response to projected climate change. In the Juncal catchment in Chile, runoff is likely to sharply decrease in the future and the runoff seasonality is sensitive to projected climatic changes. In the Langtang catchment in Nepal, future water availability is on the rise for decades to come with limited shifts between seasons. Owing to the high spatiotemporal resolution of the simulations and process complexity included in the modeling, the response times and the mechanisms underlying the variations in glacier area and river flow can be well constrained. The projections indicate that climate change adaptation in Central Chile should focus on dealing with a reduction in water availability, whereas in Nepal preparedness for flood extremes should be the policy priority. [ABSTRACT FROM AUTHOR]

Here we review the literature preferentially concerned with modern glacier-climate modeling along the Andes. We find a diverse range of modeling approaches, from empirical/statistical models to relatively complex energy balance procedures. We analyzed these models at three different spatial scales. First, we review global approaches that have included the Andes. Second, we depict and analyze modeling exercises aimed at studying Andean glaciers as a whole. Our revision shows only two studies dealing with glacier modeling at this continental scale. We contend that this regional approach is increasingly necessary because it allows for connecting the 'average-out' tendency of global studies to local observations or models, in order to comprehend scales of variability and heterogeneity. Third, we revise small-scale modeling, finding that the overwhelming number of studies have targeted glaciers in Patagonia. We also find that most studies use temperature-index models and that energy balance models are still not widely utilized. However, there is no clear spatial pattern of model complexity. We conclude with a discussion of both the limitations of certain approaches, as for example the use of short calibration periods for long-term modeling, and also the opportunities for improved understanding afforded by new methods and techniques, such as climatic downscaling. We also propose ways to future developments, in which observations and models can be combined to improve current understanding of volumetric glacier changes and their climate causes. [ABSTRACT FROM AUTHOR]

This article examines the role of glacial retreat on human migration in the Bolivian Andes-a topic with virtually no scholarly focus, yet of critical importance in the era of global climate change. Glacial melting has increased since the 1980s, and popular reports often suggest there will be significant impacts on local populations, including migration. Based on interviews with local residents, both migrants and nonmigrants, as well as topical experts, this study suggests that residents do, indeed, have serious concerns about future livelihood conditions in the Bolivian Andes. Even so, glacial retreat has not triggered new migration flows and has had a limited impact on the existing migratory patterns. [ABSTRACT FROM AUTHOR]

ABSTRACT Glacier and permafrost hazards such as glacial-lake outburst floods and rock-ice avalanches cause significant socio-economic damages worldwide, and these processes may increase in frequency and magnitude if the atmospheric temperature rises. In the extratropical Andes nearly 200 human deaths were linked to these processes during the twentieth century. We analysed bibliographical sources and satellite images to document the glacier and permafrost dynamics that have caused socio-economic damages in this region in historic time (including glacial lake outburst floods, ice and rock-ice avalanches and lahars) to unravel their causes and geomorphological impacts. In the extratropical Andes, at least 15 ice-dammed lakes and 16 moraine-dammed lakes have failed since the eighteenth century, causing dozens of floods. Some floods rank amongst the largest events ever recorded (5000 × 106 m3 and 229 × 106 m3, respectively). Outburst flood frequency has increased in the last three decades, partially as a consequence of long-term (decades to centuries) climatic changes, glaciers shrinkage, and lake growth. Short-term (days to weeks) meteorological conditions (i.e. intense and/or prolonged rainfall and high temperature that increased meltwater production) have also triggered outburst floods and mass movements. Enormous mass failures of glaciers and permafrost (> 10 × 106 m3) have impacted lakes, glaciers, and snow-covered valleys, initiating chain reactions that have ultimately resulted in lake tsunamis and far-reaching (> 50 km) flows. The eruption of ice-covered volcanoes has also caused dozens of damaging lahars with volumes up to 45 × 106 m3. Despite the importance of these events, basic information about their occurrence (e.g. date, causes, and geomorphological impact), which is well established in other mountain ranges, is absent in the extratropical Andes. A better knowledge of the processes involved can help to forecast and mitigate these events. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

High flows are major disturbances in streams and cause benthic communities to vary temporally. Meltwater runoff in glacier-fed streams at temperate-arctic latitudes primarily follows a strong seasonal pattern. In contrast, such streams at the equator show less seasonal, but more-pronounced diel variability in discharge that tracks a year-round diurnal melting-nocturnal freezing cycle of glaciers. Consequently, qualitative and quantitative differences in temporal variability of macrobenthos communities should be expected between highlatitude and tropical glacier-fed streams. We explored temporal variability in density, taxon richness, and community composition of benthic macroinvertebrates and analyzed community responses to flow events at 3 sites along a glacier-fed stream in equatorial Ecuador (0.05, 1.6, and 4.3 km from the glacier front). We obtained continuous flow recordings and sampled fauna at approximately quarterly intervals over 30 mo. Temporal variability in the fauna was aseasonal. However, the overall magnitude of the coefficient of variability (CV) at the 3 sites was not lower than the CV at temperate latitudes. The explanatory power of flow did not differ among discharge parameters 3, 6, 9, 21, and 45 d before sampling. The effect of flow (slopes of regressions of faunal metrics vs flow) did not differ among sites, but the amount of variation explained by flow was significant only at the 2 downstream sites. Little synchrony was found in variability among sites, possibly because of differences among sites in physical characteristics (e.g., refugia space), which moderated the effect of disturbances, and taxonomic composition of communities. Our study is the first to show a close link between hydrological and biological fluctuations in an equatorial glacier-fed stream, a prerequisite for subsequent predictions of consequences of tropical glacier melting on diversity, composition, and stability of stream communities. [ABSTRACT FROM AUTHOR]

Climate change is expected to reduce water security in arid mountain regions around the world. Vulnerable water supplies in semi-arid zones, such as the Dry Andes, are projected to be further stressed through changes in air temperature, precipitation patterns, sublimation, and evapotranspiration. Together with glacier recession this will negatively impact water availability. While glacier hydrology has been the focus of scientific research for a long time, relatively little is known about the hydrology of mountain permafrost. In contrast to glaciers, where ice is at the surface and directly affected by atmospheric conditions, the behaviour of permafrost and ground ice is more complex, as other factors, such as variable surficial sediments, vegetation cover, or shallow groundwater flow, influence heat transfer and time scales over which changes occur. The effects of permafrost on water flow paths have been studied in lowland areas, with limited research in the mountains. An understanding of how permafrost degradation and associated melt of ground ice (where present) contribute to streamflow in mountain regions is still lacking. Mountain permafrost, particularly rock glaciers, is often conceptualized as a (frozen) water reservoir; however, rates of permafrost ground ice melt and the contribution to water budgets are rarely considered. Additionally, ground ice and permafrost are not directly visible at the surface; hence, uncertainties related to their three-dimensional extent are orders of magnitude higher than those for glaciers. Ground ice volume within permafrost must always be approximated, further complicating estimations of its response to climate change. This review summarizes current understanding of mountain permafrost hydrology, discusses challenges and limitations, and provides suggestions for areas of future research, using the Dry Andes as a basis. [ABSTRACT FROM AUTHOR]

The area studied includes a little-known portion on the Dry Andes of the San Juan Frontal Cordillera, Argentina, where the hydrological significance of glaciers and rock glaciers was earlier never studied. The surveyed sector includes Cerro El Potro (5,870 m ASL) and nearby mountain chains (28°S). The predominant landforms in these areas were shaped in a periglacial environment superimposed on an earlier glacial landscape. These regions comprise abundant rock glaciers, a noteworthy rock glacier zone in the world, of which little is known in South America. This work employs geomorphological mapping to analyze the distribution of active rock glaciers in relation to altitude, aspect and slope using optical remote sensing techniques with GIS. Statistical estimation techniques were used based on a Digital Elevation Model (DEM) and aerial photos and Spot images interpretation. The specific density of rock glaciers' estimation in the surveyed area (Argentine border) is 1.56% with corresponds to 38 rock glaciers with an area of 5.86 km and 0.12 km of water equivalent. Furthermore, the analytical results show that elevations >4,270 m ASL, a southeast-facing aspect, and slope between 2° and 40° favor the existence of rock glaciers, Finally, a comparison with glacier water equivalent, which covers an area of ~16 km and 0.9 km of water equivalent, shows that glaciers are the main stores of water at 28°S (Cerro El Potro Glacier). However, the importance of rock glaciers as water reserves in this portion of Argentina should not be underestimated. [ABSTRACT FROM AUTHOR]

The article presents a study on glacier changes in the Pascua-Lama region of the Chilean Andes mountain range. It mentions glaciological surface mass balance measurements from four ice bodies in the area involving the nature of the ice mass and significance of mass balance to variability. It also notes changes in the surface area of ice bodies in the region since 1955 along with climatic factors.

The height of mountain ranges reflects the balance between tectonic rock uplift, crustal strength and surface denudation. Tectonic deformation and surface denudation are interdependent, however, and feedback mechanisms—in particular, the potential link to climate—are subjects of intense debate. Spatial variations in fluvial denudation rate caused by precipitation gradients are known to provide first-order controls on mountain range width, crustal deformation rates and rock uplift. Moreover, limits to crustal strength are thought to constrain the maximum elevation of large continental plateaus, such as those in Tibet and the central Andes. There are indications that the general height of mountain ranges is also directly influenced by the extent of glaciation through an efficient denudation mechanism known as the glacial buzzsaw. Here we use a global analysis of topography and show that variations in maximum mountain height correlate closely with climate-controlled gradients in snowline altitude for many high mountain ranges across orogenic ages and tectonic styles. With the aid of a numerical model, we further demonstrate how a combination of erosional destruction of topography above the snowline by glacier-sliding and commensurate isostatic landscape uplift caused by erosional unloading can explain observations of maximum mountain height by driving elevations towards an altitude window just below the snowline. The model thereby self-consistently produces the hypsometric signature of the glacial buzzsaw, and suggests that differences in the height of mountain ranges mainly reflect variations in local climate rather than tectonic forces. [ABSTRACT FROM AUTHOR]

Geomorphological mapping, sedimentology, lichenometry and dendrochronology were used to assess the nature and timing of glacier recession, moraine development and catastrophic mass movements in a tributary of the Leones valley, east of the Hielo Patagónico Norte, Chile. We show that during the 'Little Ice Age' Glaciar Calafate advanced downvalley to produce a terminal moraine. Recession of the glacier from this position occurred in the 1870s and produced a moraine dammed lake. In late 2000 a large rockfall into the lake breached the moraine and triggered a glacial lake outburst flood (GLOF) that entrained and subsequently deposited some 2 × 106 m3 of material. We interpret this event as a delayed paraglacial response to the retreat of Glaciar Calafate during the twentieth century. [ABSTRACT FROM AUTHOR]

Glacial geologic evidence and radiocarbon-dated glacial deposits provide evidence of glacier fluctuations during the last 5 ka years in the Andes. Radiocarbon-dated moraines, morphological and stratigraphical studies permit the reconstruction of glacier fluctuations during the Holocene in the Valenzuela area of the Mendoza Andes valley located at 35°S, in the upper Río Grande basin. The Holocene record in this part of the Andes is mostly unknown, so this research is relevant for palaeoclimatic reconstructions in South America. In the Río Valenzuela, glacier variations were dated in the El Azufre and El Peñón valleys. The first Neoglacial advance occurred at c. 5700 yr BP and a very close re-advance of similar magnitude occurred at 4700–4300 yr BP which formed well-preserved lateral-terminal moraines. The first Neoglacial advance occurred in the El Peñón valley at c. 4400 yr BP and a well-preserved terminal moraine is observed. A second Neoglacial advance reached its maxima at c. 2500–2200 yr BP in the El Azufre and El Peñón glaciers. A third, corresponding to the 'Little Ice Age', culminated at c. 400 yr BP (c. AD 1451–1641 cal. yr) and 350±60 yr BP (c. AD 1460–1644 cal. yr) in the El Azufre valley. The third Neoglacial advance is distinguished in the El Peñón valley based on morphological characteristics, colour, freshness of the glacial deposits and the proximity to the active glacier. It is indicated by the Amarilla I, II, III lateral moraines. An estimation of the magnitude of snowline depression is obtained comparing the altitude of the present snowline with that of the reconstructed snow line for the first Neoglacial and 'Little Ice Age' advances. [ABSTRACT FROM AUTHOR]

Abrupt warming events recorded in Greenland ice cores known as Dansgaard-Oeschger (DO) interstadials are linked to changes in tropical circulation during the last glacial cycle. Corresponding variations in South American summer monsoon (SASM) strength are documented, most commonly, in isotopic records from speleothems, but less is known about how these changes affected precipitation and Andean glacier mass balance. Here we present a sediment record spanning the last ~50 ka from Lake Junín (Peru) in the tropical Andes that has sufficient chronologic precision to document abrupt climatic events on a centennial-millennial time scale. DO events involved the near-complete disappearance of glaciers below 4700 masl in the eastern Andean cordillera and major reductions in the level of Peru's second largest lake. Our results reveal the magnitude of the hydroclimatic disruptions in the highest reaches of the Amazon Basin that were caused by a weakening of the SASM during abrupt arctic warming. Accentuated warming in the Arctic could lead to significant reductions in the precipitation-evaporation balance of the southern tropical Andes with deleterious effects on this densely populated region of South America. How the abrupt warming events recorded in Greenland ice cores during the last glacial cycle have influenced the tropical climate is not well known. Here the authors present new lake sediment data from the Peruvian Andes that shows that these events resulted in rapid glacier retreat and large reductions in lake level. [ABSTRACT FROM AUTHOR]

Different water related risks such as lake outburst floods and water scarcity are typically assessed by separate methods and often by separate research communities. However, in a local context such as in mountain regions of the developing world different water risks are intertwined and shaped by multi-dimensional natural and socio-economic drivers. Progressing glacier melt and the associated growing number of lakes rises the threat of glacier lake outburst floods (GLOFs); at the same time declining melt water supply changes the hydrological regime, resulting in changing water availability, especially during dry seasons. Here, we address this challenge by integratively assessing water scarcity and GLOF risks and their interactions for two study sites in glacierized catchments in the Cordillera Blanca and Urubamba in the Peruvian Andes. We used hydrological modelling, GLOF flow path modelling, and interviews with local people and technical experts to assess the hazard and risks of water scarcity and GLOFs. We incorporate perspectives of people living in those areas in order to gain a more comprehensive view on risks. While metrics of flood and water scarcity hazards are difficult to compare, we found insightful results using a comparative analysis of elements at risk from different water related hazards with different probabilities of occurrence. Furthermore, our study shows that considering the diverse local perspectives on risks as well as the social, cultural, economic and political context is essential to more successful and sustainable disaster risk reduction, climate change adaptation and integrated water management. [ABSTRACT FROM AUTHOR]

Glaciers in the central Andes of Chile are fundamental freshwater sources for ecosystems and communities. Overall, glaciers in this region have shown continuous recession and down-wasting, but long-term glacier mass balance studies providing precise estimates of these changes are scarce. Here, we present the first long-term (1955–2013/2015), region-specific glacier elevation and mass change estimates for the Maipo River Basin, from which the densely populated metropolitan region of Chile obtains most of its freshwater supply. We calculated glacier elevation and mass changes using historical topographic maps, Shuttle Radar Topography Mission (SRTM), TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X), and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results indicated a mean regional glacier mass balance of −0.12 ± 0.06 m w.e.a−1, with a total mass loss of 2.43 ± 0.26 Gt for the Maipo River Basin between 1955–2013. The most negative glacier mass balance was the Olivares sub-basin, with a mean value of −0.29 ± 0.07 m w.e.a−1. We observed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, and more negative values between 2000 and 2013, with an acceleration in ice thinning rates starting in 2010, which coincides with the severe drought. Our results provide key information to improve glaciological and hydrological projections in a region where water resources are under pressure. [ABSTRACT FROM AUTHOR]