Glacier Ablation Zones Research Articles

The Importance of a Glacier Complex for Downstream Runoff in the Semiarid Chilean Andes During Dry Years

ABSTRACTHigh mountain catchment systems are inherently complex and include multiple processes that influence runoff generation, making it challenging to assess their current state and project their future solely based on observed data. However, combining observations with hydrological models that can simulate glacio‐hydrological processes robustly offers a solution to this issue. This study focused on analysing and characterising the snow, glacier and runoff processes of the Tapado Glacier sub‐catchment, an upstream source of the La Laguna reservoir in the semiarid Chilean Andes (30° S) for 2019–2021. For this purpose, a semi‐distributed physical model (Cold Regions Hydrological Model [CRHM]) was used to simulate glacio‐hydrological processes. The results indicate that sublimation accounted for 66%–89% of snow ablation, limiting the amount of snow available for melting in summer, and making melt from Tapado Glacier the primary component of mid‐summer (January) discharge (28%–55%). This was reflected in significant mass loss from the Tapado Glacier ablation zone (−0.5 to −2.1 m w.e.). Sensitivity analyses indicated that precipitation and snow roughness generated the greatest variability in simulations related to snow mass balance process. Uncertainty due to errors in precipitation measurement and extrapolation is inherent in hydrological modelling in most mountain settings, whilst the uncertainty related to snow roughness (evaluated range: 0.0001–0.1 m) is largely due to its direct influence on snow sublimation rates and the challenges associated with measuring this variable. For the glaciated areas, results were sensitive to the selection of ice albedo. Whilst the Tapado sub‐catchment includes only 1% of the catchment feeding the La Laguna reservoir (c.a. 27 km downstream), it equates to 6%–26% of monthly inflow into the reservoir over the study period. This indicates the importance of glaciated regions for supporting baseflow during relatively dry periods.

A reassessment of ice cliff dynamics upon debris-covered glaciers

Abstract We present a new model for understanding ice cliff dynamics within a debris-covered glacier ablation zone. This simple energy-balance model incorporates a moving frame of reference, made necessary by the melt of the surrounding debris-covered ice. In so doing, this also formalises how different types of field measurements can be utilised and compared. Our predictions include showing: ice cliffs can endogenously select their own slope angles; that there should be an indifference between illuminated north- and south-facing ice cliff slopes; that ice cliffs grow steeper with thicker debris layers; that ice cliffs cannot stably exist below a certain critical debris thickness and that some modelling of ice cliffs (when not incorporating the moving frame) may incorrectly estimate ice mass losses. All of our results are produced using parametrisations from Baltoro Glacier, Karakoram.

Supraglacial geomorphology of Companion Glacier, central Himalaya: evolution, controls and consequences

Supraglacial debris cover greatly influences glacier dynamics. The present study combines field and remote sensing observations acquired between 2000 and 2020 to understand debris characteristics, area and terminus changes, surface velocity, and mass balance of the Companion Glacier, Central Himalaya, along with a systematic investigation of its supraglacial morphology. According to field observations, the glacier’s lower ablation zone has very coarse and thick debris (1–3 m). Owing to thick debris and consequent protected margins, the glacier could maintain its geometry during the study (2000–2020) showing much less area loss (0.07% ±0.1% a−1) and terminus retreat (1.2 ±1.9 m a−1) than other glaciers in the study region. The average mass balance (−0.12 ±0.1 m w. e. a−1; 2000–2020) was also less negative than the regional trend. Interestingly, in contrast to widespread regional velocity reduction, Companion’s average velocity increased (by 21%) from 6.97 ±3.4 (2000/01) to 8.45 ±2.1 m a−1 (2019/20). Further, to investigate supraglacial morphology, the glacier ablation zone is divided into five zones (Zone-I to V; snout-to-up glacier) based on 100 m altitude bins. Analysis reveals that stagnation prevails over Zone-I to Zone-III, where despite slight acceleration, the velocity remains <∼8 m a−1. Zone-V is quite active (12.87 ±2.1 m a−1) and has accelerated during the study. Thus, Zone-IV with stable velocity, is sandwiched between fast-moving Zone-V and slow-moving Zone-III, which led to bulging and development of mounds. Debris slides down these mounds exposing the top portion for direct melting and the meltwater accumulates behind the mounds forming small ponds. Thus, as a consequence of changing morphology, a new ablation mechanism in the form of spot-melting has dominated Zone-IV, leading to the highest negative mass balance here (−0.5 ±0.1 m w. e. a−1). The changing snout and supraglacial morphology, active mound-top’s melting and formation of ponds likely promote relatively higher glacier wastage in the future.

Dust dominates the summer melting of glacier ablation zones on the northeastern Tibetan Plateau

Dust and black carbon (BC) can darken snow and ice surface and play pivotal roles in glacier mass loss. Thus, a quantitative assessment of their contributions to glacier summer melting is critical. During the summer of 2018, surface snow and ice were sampled, and the albedo and mass balance were continuously measured in the ablation zone of Laohugou Glacier No. 12 in the western Qilian Mountains. The physical properties of dust and BC were measured in the laboratory, and their impacts on glacier surface albedo reduction and melting were simulated. The results indicate that the ice surface in the ablation zone was enriched with substantial amounts of particles, and the average particle concentrations of these samples were hundreds of times higher than those of fresh snow. The BC mass absorption cross-sections (MACs) ranged from 3.1 m2 g−1 at 550 nm for dirty ice to 4.6 m2 g−1 for fresh snow, largely owing to meltwater percolation and particle collapse. The spectral variations in dust MACs were significantly different in the visible light bands and near-infrared bands from those in the other areas. Moreover, the two-layer surface energy and mass balance model with the new albedo parameterization formula was validated and agreed well with the experimental measurements of spectral albedo, broadband albedo, and mass balance. BC and dust combined resulted in 26.7 % and 54.4 % of the total mass loss on the cleaner and dirtier (particle enriched) surfaces in the ablation zone, respectively, compared to particle-free surfaces, and although both impurities played vital roles, dust was the more prominent factor in accelerating glacier melting on the northeastern Tibetan Plateau. This study emphasizes the importance of dust in cryosphere changes where Tibetan glaciers are strongly affected by Asian dust deposition.

De-icing landsystem model for the Universidad Glacier (34° S) in the Central Andes of Chile during the past ~660 years

Reconstructing latest Holocene (<1000 years) glacial landscape development in the Central Andes of Chile (30–35° S) is key for understanding the response of the cryosphere during periods of negative glacier mass balance, such as the current one. The excellently preserved glacial landscape produced during the latest ice advance and retreat cycle is of particular interest for examining the detailed response of glaciers to deglaciation. To establish a conceptual model of glacier behavior under warm and dry climatic conditions, we reconstructed and dated the recent glacial history of the Universidad Glacier (34° S) through detailed geomorphological mapping and 10Be cosmogenic surface exposure dating. Our mapping describes a landsystem that spans from the current ice front to ~3 km down-valley, where a mosaic of glacial landforms includes mounded relief; sinkholes; debris-filled stripes; moraine belts; flutings; and a prominent basal till plain. Our 10Be ages suggest that the Universidad Glacier has fluctuated in its forefield since the 13th – 15th centuries CE. We propose that the glacier evolved from a clean glacier to a debris-covered glacier, to an ice-cored moraine, and finally, to a massive dead-ice topography. This deglacial evolution intermittent and potentially reset by multiple standstills and/or re-advances during the overall retreat. The implication is that phases of active ice were followed by stagnation associated with progressive melting of dead ice under the supraglacial debris layer. Similar geomorphic features and processes are recorded in the present-day Universidad Glacier ablation zone, denoting a recurrent reconditioning over time analogous to the glacier's evolution during the latest Holocene.

A long-term dataset of climatic mass balance, snow conditions, and runoff in Svalbard (1957–2018)

Abstract. The climate in Svalbard is undergoing amplified change compared to the global mean. This has major implications for runoff from glaciers and seasonal snow on land. We use a coupled energy balance–subsurface model, forced with downscaled regional climate model fields, and apply it to both glacier-covered and land areas in Svalbard. This generates a long-term (1957–2018) distributed dataset of climatic mass balance (CMB) for the glaciers, snow conditions, and runoff with a 1 km×1 km spatial and 3-hourly temporal resolution. Observational data including stake measurements, automatic weather station data, and subsurface data across Svalbard are used for model calibration and validation. We find a weakly positive mean net CMB (+0.09 m w.e. a−1) over the simulation period, which only fractionally compensates for mass loss through calving. Pronounced warming and a small precipitation increase lead to a spatial-mean negative net CMB trend (−0.06 m w.e. a−1 decade−1), and an increase in the equilibrium line altitude (ELA) by 17 m decade−1, with the largest changes in southern and central Svalbard. The retreating ELA in turn causes firn air volume to decrease by 4 % decade−1, which in combination with winter warming induces a substantial reduction of refreezing in both glacier-covered and land areas (average −4 % decade−1). A combination of increased melt and reduced refreezing causes glacier runoff (average 34.3 Gt a−1) to double over the simulation period, while discharge from land (average 10.6 Gt a−1) remains nearly unchanged. As a result, the relative contribution of land runoff to total runoff drops from 30 % to 20 % during 1957–2018. Seasonal snow on land and in glacier ablation zones is found to arrive later in autumn (+1.4 d decade−1), while no significant changes occurred on the date of snow disappearance in spring–summer. Altogether, the output of the simulation provides an extensive dataset that may be of use in a wide range of applications ranging from runoff modelling to ecosystem studies.

Narrowband signals recorded near a moulin that are not moulin tremor: a cautionary short note

AbstractGeophysicists that deploy seismic sensors in ablation zones of glaciers and ice sheets to record glaciogenic signatures can confront recording challenges caused by instrument melt-out or tilt. These challenges often require installing sensors in boreholes to delay melt-out, or securing sensors to structures that improve coupling. We show that some of these structures that were buried near a moulin at a snow-free site in the ablation zone of the Western Greenland Ice Sheet resonated as they became exposed, and caused their geophones to record temporally evolving, narrowband signals that mimic features of glaciogenic sources like moulin tremor. We quantify these artifacts with a mechanical model that shows instruments undergo structural resonance as they melt-out, at exposure rates that we predict from an ablation model (RACMO). These models reproduce general spectral features in our data, and enable us to estimate what instrument exposure reduces ice-to-sensor coupling enough to prevent icequake detection. Last, we use our resonance data to quantitatively measure how narrowband signals that originate from either artificial or glaciogenic sources will reduce the ability of certain waveform detectors (correlators) to capture transient seismic events, even if sensors remain coupled.

Accelerated Volume Loss in Glacier Ablation Zones of NE Greenland, Little Ice Age to Present

AbstractMountain glaciers at the periphery of the Greenland ice sheet are a crucial freshwater and sediment source to the North Atlantic and strongly impact Arctic terrestrial, fjord, and coastal biogeochemical cycles. In this study we mapped the extent of 1,848 mountain glaciers in NE Greenland at the Little Ice Age. We determined area and volume changes for the time periods Little Ice Age to 1980s and 1980s to 2014 and equilibrium line altitudes. There was at least 172.76 ± 34.55‐km3 volume lost between 1910 and 1980s, that is, a rate of 2.61 ± 0.52 km3/year. Between 1980s and 2014 the volume lost was 90.55 ± 18.11 km3, that is, a rate of 3.22 ± 0.64 km3/year, implying an increase of ~23% in the rate of ice volume loss. Overall, at least ~7% of mass loss from Greenland mountain glaciers and ice caps has come from the NE sector.

Spheroidal carbonaceous particles in cryoconite sediment on the Russell glacier, Southwest Greenland

In this study, we analysed the organic and inorganic content of the cryoconite holes along the altitudinal gradient at the lower elevations of the Russell glacier ablation zone in Southwest Greenland. We specifically focus on less studied industrial microscopic spheroidal carbonaceous particles (SCP; part of black carbon) to get more insights about their accumulation patterns on the glacier surface. We found no clear SCP distribution pattern, including concentration values. This outcome underlines the complexity of the ice margin zone and draws attention for further research on this topic with the inclusion of multiyear evaluation of SCP concentration at the even wider area that could possibly give results that can be compared to the emission source and long-way air pollution validation. In addition, our results indicate that during the summer of 2016, algae composition was formed of both green algae (Chlamydomonadaceae, Mesotaeniaceae) and cyanobacteria (Oscillatoriaceae). Green algae had a larger relative proportion than cyanobacteria in the cryoconite holes throughout the studied gradient.

Understanding Mercury Cycling in Tibetan Glacierized Mountain Environment: Recent Progress and Remaining Gaps.

Glacierized mountain environments can preserve and release mercury (Hg) and play an important role in regional Hg cycling. In the Tibetan Plateau (TP), most glaciers have been retreating at unprecedented rate in recent decades, acting as one of the most active factors in regional hydrological cycling. In this mini-review, we summarized recent studies on Hg distribution, transport, and accumulation in Tibetan glacierized environments. We highlight that melting glacier may represent a stimulator that exports Hg to glacier-fed ecosystems. We identified major knowledge gaps and proposed future research needs with several emphases, including quantifying Hg in glacier ablation zone, depicting Hg transport and transformation in glacial rivers during spring melt season, and better constraining glacier-export Hg and its environmental risks to the downstream. Besides, Hg isotopic technical, passive sampling and hydrological transport model should be utilized to improve the understanding of Hg cycling in high mountain regions in the TP.

Basal control of supraglacial meltwater catchments on the Greenland Ice Sheet

Abstract. Ice surface topography controls the routing of surface meltwater generated in the ablation zones of glaciers and ice sheets. Meltwater routing is a direct source of ice mass loss as well as a primary influence on subglacial hydrology and basal sliding of the ice sheet. Although the processes that determine ice sheet topography at the largest scales are known, controls on the topographic features that influence meltwater routing at supraglacial internally drained catchment (IDC) scales (&lt;10s of km) are less well constrained. Here we examine the effects of two processes on ice sheet surface topography: transfer of bed topography to the surface of flowing ice and thermal–fluvial erosion by supraglacial meltwater streams. We implement 2-D basal transfer functions in seven study regions of the western Greenland Ice Sheet ablation zone using recent data sets for bed elevation, ice surface elevation, and ice surface velocities. We find that ∼1–10 km scale ice surface features can be explained well by bed topography transfer in regions with different multiyear-averaged ice flow conditions. We use flow-routing algorithms to extract supraglacial stream networks from 2 to 5 m resolution digital elevation models and compare these with synthetic flow networks calculated on ice surfaces predicted by bed topography transfer. Multiple geomorphological metrics calculated for these networks suggest that bed topography can explain general ∼1–10 km supraglacial meltwater routing and that thermal–fluvial erosion thus has a lesser role in shaping ice surface topography on these scales. We then use bed topography transfer functions and flow routing to conduct a parameter study predicting how supraglacial IDC configurations and subglacial hydraulic potential would change under varying multiyear-averaged ice flow and basal sliding regimes. Predicted changes to subglacial hydraulic flow pathways directly caused by changing ice surface topography are subtle, but temporal changes in basal sliding or ice thickness have potentially significant influences on IDC spatial distribution. We suggest that changes to IDC size and number density could affect subglacial hydrology primarily by dispersing the englacial–subglacial input of surface meltwater.

TerraSAR-X/TanDEM-X data for natural hazards research in mountainous regions of Uzbekistan

Accurate and up-to-date digital elevation models (DEMs) are important tools for studying mountain hazards. We considered natural hazards related to glacier retreat, debris flows, and snow avalanches in two study areas of the Western Tien-Shan mountains, Uzbekistan. High-resolution DEMs were generated using single TerraSAR-X/TanDEM-X datasets. The high quality and actuality of the DEMs were proved through a comparison with Shuttle Radar Topography Mission, Advanced Spaceborne Emission and Reflection Radiometer, and Topo DEMs, using Ice, Cloud, and Land Elevation Satellite data as the reference dataset. For the first study area, which had high levels of economic activity, we applied the generated TanDEM-X DEM to an avalanche dynamics simulation using RAMMS software. Verification of the output results showed good agreement with field observations. For the second study area, with a wide spatial distribution of glaciers, we applied the TanDEM-X DEM to an assessment of glacier surface elevation changes. The results can be used to calculate the local mass balance in glacier ablation zones in other areas. Models were applied to estimate the probability of moraine-dammed lake formation and the affected area of a possible debris flow resulting from glacial lake outburst. The natural hazard research methods considered here will minimize costly ground observations in poorly accessible mountains and mitigate the impacts of hazards on the environment of Uzbekistan.

Changes in the ablation zones of glaciers in the western Himalaya and the Karakoram between 1972 and 2015

Observed estimates of changes in the Himalayan and Karakoram glaciers remain ambiguous because of limited knowledge regarding complex glacier behaviour, low quality of remote sensing data, and sparse ground-based monitoring. Remote sensing has indicated anomalous behaviour of glaciers in the Karakoram during the past two decades, attracting scientists' attention to the region. In this context, this study has made detailed estimates of changes in thickness and area of two glaciers (the Sachen in the western Himalaya and the Burche in the Karakoram) to facilitate understanding of recent glacier changes and their potential impacts on water resources. This study used several datasets, including Landsat, the Shuttle Radar Topographic Mission (SRTM), the Ice, Cloud and Land Elevation Satellite (ICESat), and differential Global Positioning System (dGPS) in-situ measurements, from the period 1972 through 2015. The extent of debris cover increased significantly between 1972 and 2014, while the total glacierized area decreased slightly. Further, our study estimated thickness changes after removing recognizable biases and seasonal variations, computed through comparisons of ICESat data with dGPS. A thinning trend occurred between 2000 and 2015, suggesting that the glaciers in the western part of the Karakoram and Himalaya regions have not recently gained mass. This study also found non-uniform variations within different zones of the glaciers. Avalanches have fed most of the Karakoram glaciers, providing spatially heterogeneous thickness changes. The frequency of observations, data quality, acquisition time, and local weather affect our observations of temporal changes. Careful assessment of regularly acquired remote-sensing and ground-based observations should reduce uncertainty regarding estimates of glacier changes for management of water resources and associated hazards.

Interaction between climate, volcanism, and isostatic rebound in Southeast Alaska during the last deglaciation

Observations of enhanced volcanic frequency during the last deglaciation have led to the hypothesis that ice unloading in glaciated volcanic terrains can promote volcanism through decompression melting in the shallow mantle or a reduction in crustal magma storage time. However, a direct link between regional climate change, isostatic adjustment, and the initiation of volcanism remains to be demonstrated due to the difficulty of obtaining high-resolution well-dated records that capture short-term climate and volcanic variability traced to a particular source region. Here we present an exceptionally resolved record of 19 tephra layers paired with foraminiferal oxygen isotopes and alkenone paleotemperatures from marine sediment cores along the Southeast Alaska margin spanning the last deglacial transition. Major element compositions of the tephras indicate a predominant source from the nearby Mt. Edgecumbe Volcanic Field (MEVF). We constrain the timing of this regional eruptive sequence to 14.6–13.1 ka. The sudden increase in volcanic activity from the MEVF coincides with the onset of Bølling–Allerød interstadial warmth, the disappearance of ice-rafted detritus, and rapid vertical land motion associated with modeled regional isostatic rebound in response to glacier retreat. These data support the hypothesis that regional deglaciation can rapidly trigger volcanic activity. Rapid sea surface temperature fluctuations and an increase in local salinity (i.e., δ18Osw) variability are associated with the interval of intense volcanic activity, consistent with a two-way interaction between climate and volcanism in which rapid volcanic response to ice unloading may in turn enhance short-term melting of the glaciers, plausibly via albedo effects on glacier ablation zones.

Distributed modeling of ablation (1996–2011) and climate sensitivity on the glaciers of Taylor Valley, Antarctica

ABSTRACTThe McMurdo Dry Valleys of Antarctica host the coldest and driest ecosystem on Earth, which is acutely sensitive to the availability of water coming from glacial runoff. We modeled the spatial variability in ablation and assessed climate sensitivity of the glacier ablation zones using 16 years of meteorological and surface mass-balance observations collected in Taylor Valley. Sublimation was the primary form of mass loss over much of the ablation zones, except for near the termini where melt, primarily below the surface, dominated. Microclimates in ~10 m scale topographic basins generated melt rates up to ten times higher than over smooth glacier surfaces. In contrast, the vertical terminal cliffs on the glaciers can have higher or lower melt rates than the horizontal surfaces due to differences in incoming solar radiation. The model systematically underpredicted ablation for the final 5 years studied, possibly due to an increase of windblown sediment. Surface mass-balance sensitivity to temperature was ~−0.02 m w.e. K−1, which is among the smallest magnitudes observed globally. We also identified a high sensitivity to ice albedo, with a decrease of 0.02 having similar effects as a 1 K increase in temperature, and a complex sensitivity to wind speed.

Microbial community changes along the Ecology Glacier ablation zone (King George Island, Antarctica)

In recent years, glacial surfaces have received much attention as microbial habitats of diverse photoautotrophic and heterotrophic cells. Supraglacial ecosystems are annually covered and uncovered by snow. The aim of this study is to investigate the microbial community response to changing environmental conditions in a transect following the receding snow line on the surface of Ecology Glacier (King George Island, Antarctica). Parameters of surface ice and cryoconite holes included chemical composition of ice and sediment, Bacteria diversity by denaturating gradient gel electrophoresis, microbial functional diversity (Biolog Ecoplates), and microbial counts (epifluorescence microscopy, colony-forming units). Data demonstrated profound differences between surface ice and cryoconite holes. Changing environmental factors along the transect influenced composition and abundance of the microbiocenosis in both habitat types. Several parameters correlated positively with distance from the glacier edge, including the cell morphotype Shannon index, chlorophyll a, nitrogen, and seston concentrations. Suspended solid content positively correlated with microbial abundance and diversity. Nitrogen and phosphorus were limiting factors of microbial growth as amounts of organic nitrogen and phosphorus positively correlated with the cell numbers, fission rates, and photoautotroph contribution. Our findings indicate that microbial community shows a response in terms of abundance and diversity to exposure of the glacial surface as snow-cover melts. To our knowledge, this is the first study to recognize a microbial development pattern on a glacier surface in connection with the receding snow line. This may help better understand variability within supraglacial habitats, correct sampling procedures, and inform biocenotic development models.

Surficial geology and geomorphology of the Kumtor Gold Mine, Kyrgyzstan: human impacts on mountain glacier landsystems

ABSTRACTA 1:50,000 scale map of the surficial geology and geomorphology of the mountain glacier landsystem and the human impacts of the Kumtor Gold Mine operations in the Akshiirak massif was compiled from a 0.5 m resolution pan-sharpened image from Digital Globe's WorldView-2 platform dated 5 September 2014. The map depicts 11 surficial geology units, 6 of which are classified according to natural genetic origins and 5 relating to recent human interference with glaciological and land surface processes. When compared to historical imagery the map records a number of important, not unrelated, cryospheric responses to mining activity, including: (a) the triggering of human-induced glacier speed-up events or surges due to dumping of mine spoil on receding and thinning glacier snouts; (b) the reactivation by internal creep of buried glacier ice due to the expansion of spoil dumping onto down valley areas of ice-cored moraine; and (c) accelerated ice drawdown and significant incursions of ice into the mine pit walls due to the artificial removal of substantial areas of glacier ablation zones.

Change in glacier area and thickness in the Tomur Peak, western Chinese Tien Shan over the past four decades

This paper looks at glacier area change in the Tomur Peak for the 1964/71–2000 and 2000–2011 periods. The results show that the total area of the selected 78 glaciers has decreased from 555.45 km2 in 1964/71 to 530.39 km2 in 2000, and further reduced to 521.89 km2 in 2011. Overall, the selected glaciers have lost 4.50% of their surface area between 1964/71 and 2000, and have lost 1.60% more between 2000 and 2011. The area reduction rate of the 78 glaciers increased from 0.12%/a during 1964/71–2000 to 0.13%/a during 2000–2011. In addition, this paper describes a method for estimating the ice surface elevation change using the SRTM (2000) and elevation data generated from topographic maps (1964/71) to quantify the ice thickness change for the 1964/71–2000 period. The surface elevation for about 73.50% of grid area decreased, mostly in the glacier ablation zone. The overall average thickness loss is 22.35 m which yields an annual loss of 0.60 m/a.

Glacier runoff and its impact in a highly glacierized catchment in the southeastern Tibetan Plateau: past and future trends

AbstractWe investigate past and future trends in glacier runoff and the associated hydrological impacts on river runoff in the Hailuogou catchment, a highly glacierized catchment with extensive debris cover in the southeastern Tibetan Plateau, using a catchment-scale glacio-hydrological model. Past trends in various runoff components of the catchment indicate that glacier runoff has been a large component of total runoff, contributing ∼53.4% of total runoff during the period 1952–2013. Future changes in runoff calculated using the outputs of ten global climate models for representative concentration pathway (RCP) 4.5 and RCP8.5 reveal that glacier runoff plays different roles in the water supply of the catchment for the two RCPs, and the discrepancies between the two RCPs increase in the second half of this century, leading to a considerable difference in the hydrological regime of the catchment. In particular, changes are more remarkable under RCP8.5, under which all glaciers are projected to retreat dramatically and total runoff to decrease slightly by the end of this century. An experimental analysis, in which no debris cover is assumed on glacier ablation zones, indicates that excess meltwater from the debris-covered area provides an 8.1% increase in total runoff relative to the no-debris assumption case.

Empirical mass balance modelling of South American tropical glaciers: case study of Antisana volcano, Ecuador

Most Latin American glaciers are located in the tropical Andes. The melting processes of Glacier “15” on Antisana volcano were studied to understand the relationship between glacier retreat and natural climate variability and global climate change. Glaciers on the Antisana volcano are crucial sources of water as they feed the headwater rivers that supply Quito with potable water. The aim of this study was to build empirical models based on multiple correlations to reconstruct the mass loss of glaciers over a period of 10 years at three scales: local (data recorded by meteorological stations located around the volcano), regional (data from stations located around the country) and global (re-analysis data). Data quality was checked using graphical and statistical methods. Several empirical models based on multiple correlations were created to generate longer time series (42 and 115 years) of the mass balance for the glacier ablation zone. The long mass balance series were compared with the temperature variation series of the Earth’s surface in the Southern Hemisphere to estimate the relation between the mass balance and global warming. Our results suggest that the meteorological factors that best correlate with mass balance are temperature and wind.Editor D. KoutsoyiannisCitation Manciati, C., Villacís, M., Taupin, J.-D., Cadier, E., Galárraga-Sánchez, R., and Cáceres, B., 2014. Empirical mass balance modelling of South American tropical glaciers: case study of Antisana volcano, Ecuador. Hydrological Sciences Journal, 59 (8), 1519–1535. http://dx.doi.org/10.1080/02626667.2014.888490