ID06: Andean glaciers and their role in the high mountain water cycle

Abstract ID 447 | Date: 2022-09-12 10:15 – 10:30 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Fernández, Alfonso (1); Somos-Valenzuela, Marcelo (2,3); Manquehual-Cheuque, Francisco (2,3)

Among the myriad of mitigation strategies for anthropogenic climate warming, Climatic Geoengineering is one of the most controversial proposals to limit projected trajectories of temperature increase for the rest of the 21^st century. Numerical models that evaluate the sensitivity of the climate system to different types of climate engineering include those that simulate the effect of solar radiation management (SRM) in order to attenuate warming by decreasing the incoming shortwave radiation flux, the engine of the global energy balance. Under the umbrella of the IPCC,  the Geoengineering Model Intercomparison Project (GeoMIP6, part of the CMIP6) provides a number of model output, with SRM among those. While many of these models indicate that Climatic Geoengineering is able to limit global warming to levels below 1.5º to 2ºC relative to pre-industrial conditions, little is known on the regional effects associated to these mitigation approaches. Here we present results from the analysis of the impacts of the G6Solar experiment over the Andes, including temperature, precipitation, and the effect on glacier mass balance. The G6Solar experiment is part of the GeoMIP6, and simulates a climate derived from decadal decreases of the solar radiation input. We compare this experiment with the CMIP6 SSP245 and SSP585 scenarios and use a glacier mass balance model forced by these different experiments. Our results show that while G6Solar produces cooling along the Cordillera, it is not necessarily better than the SSP245 or SPP585. However, precipitation shows a pattern of drying towards the south, suggesting that there might be unintended impacts of Geoengineering on mountain hydrology. In fact, the computation of glacier mass balance using G6Solar as model input shows that many glaciers will irremediably shrink, particularly in extratropical areas, although delaying full disappearance by about a decade or in some subregions. In addition to describing these results, in this work we put forward some dynamical arguments to explain the drying trend of the G6Solar. We also discuss implications for policy-making.

Abstract ID 364 | Date: 2022-09-12 10:30 – 10:45 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Barandun, Martina (1,2); Bravo, Claudio (3); Grobety, Bernard (4); Jenk, Theo (1,5); Fang, Ling (1); Naegeli, Kathrin (6); Rivera, Andres (7); Cisternas, Sebastian (3); Muenster, Tatjana (1); Schwikowski, Margit (1,5)

We have investigated the source and role of light-absorbing impurities (LAIs) deposited on the glaciers of the Olivares catchment, in Central Chile. LAIs can considerably darken (lowering albedo) the glacier surface, enhancing their melt. We combined chemical and mineralogical laboratory analyses of surface and ice core samples with field-based spectral reflectance measurements to investigate the nature and properties such LAIs. Using remote sensing-based albedo maps, we upscaled local information to glacier-wide coverage. We then used a model to evaluate the sensitivity of surface mass balance to a change in ice and snow albedo. The across-scale surface observations in combination with ice core analysis revealed a history of over half a century of LAIs deposition. We found traces of mining residuals in glacier surface samples. The glaciers with highest mass loss in the catchment present enhanced concentrations of surface dust particles with low reflectance properties. Our results indicate that dust particles with strong light-absorbing capacity have been mobilized from mine tailings and deposited on the nearby glacier surfaces. Large-scale assessment from satellite-based observations revealed darkening (ice albedo lowering) at most investigated glacier tongues from 1989 to 2018. Mass balance is sensitive to ice albedo. However, we believe that an accelerated winter and spring snow albedo decrease, partially triggered by surface impurities, might be responsible for the above-average mass loss encountered in this catchment.

Abstract ID 446 | Date: 2022-09-12 10:45 – 11:00 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Paul, Frank; Rastner, Philipp

Glaciers in the tropical Andes of Peru and Bolivia are important water resources. Precise determination of their extent at a certain point in time is thus mandatory to provide realistic estimates of the water resources they contain or modelling of their future evolution. Unfortunately, creating precise glacier outlines in this tropical region is hampered all year round by either seasonal snow or cloud cover, both hiding the true glacier perimeter. Additionally, extended shadows created by the steep topography impact on the visibility of glaciers on south facing slopes during May to July. Accordingly, the outlines currently available from the widely used RGI6 have severe quality issues, i.e. they are often much larger than they should be for the dates they refer to.
In the framework of preparing version 7 of the RGI, we have remapped all glaciers in Peru and Bolivia from 17 Landsat Thematic Mapper scenes acquired in 1998, a year when seasonal snow off glaciers was largely absent in the entire region. All glaciers (clean ice) were mapped automatically with a standard band ratio (red/SWIR) and a scene specific threshold value. Wrongly classified lakes and missing debris cover was removed / appended by manual editing, using contrast enhanced false colour composites in the back-ground. We also used the very high-resolution satellite images available in the ESRI Basemap to aid in the interpretation of glacier parts being in shadow or under debris cover. The Copernicus DEM GLO-30 was used to derive new drainage divides as those in RGI6 were often found at a wrong location.
Overall we mapped 3586 glaciers larger than 0.01 km² covering an area of 1747.3 km². This is 419 km² or 20% less than the 2166 km² available from the RGI6. Glacier outlines in RGI6 refer to the period 2000 to 2009 according to the metadata in the attribute table. As most area change studies conducted so far in this region found continuous and strong glacier area decrease over this period, a ‘back-calculation’ of all glacier areas to the year 1998 would give an even larger glacier area for this year, and an overestimation closer to 25%. This means that also total modelled water resources are overestimated and studies presenting future glacier evolution might be wrong. The ‘new’ glacier inventory for 1998 might thus help in adjusting related values and create more realistic estimates of this valuable water resource.

Abstract ID 132 | Date: 2022-09-12 11:00 – 11:15 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Ochoa-Sánchez, Ana (1); Stone, Daíthí (2); Drenkhan, Fabian (3,4,5); Mendoza, Daniel (6); Gualán, Ronald (7); Huggel, Christian (3)

Evidence of observed climate change impacts has increased substantially in the past decade. However, understanding the interconnections among natural and human systems and how climate change affects them all is still a challenge. This is especially true for the Andes where there is insufficient research infrastructure and funding, resulting in poor data availability and quality.

We have systematically assessed observed impacts of climate change in the following natural and human systems in the Andes: cryosphere, water, wildfire, mountain hazards, energy, food security, human health, human migration, culture and tourism. In addition, we used expert and model-based methods to identify the role of anthropogenic climate change. The first is based on a comprehensive sample of literature which is analysed to distinguish between natural variability, anthropogenic forcing, and non-climatic factors that drive the observed trends. This assessment is complemented with a systematic comparison of climate model simulations against observations.

Our assessment shows that glacier loss can be attributed to anthropogenic warming with high confidence. Glacier and snow depletion have led to reduced streamflow across many regions in the Andes threatening human water security and intensifying human migration. There is robust evidence that this has also impacted mountain ecosystems, human traditions, cultures and spiritual values, mountain tourism and more frequent disasters, driven by rock falls, ice detachments or snow avalanches that, in some cases, have even triggered glacier lake outburst floods. In addition, we found that impacts related to water have affected all Andean countries with higher frequency in floods, droughts and water quality due to rising temperatures and changes in precipitation that are attributed to anthropogenic influence with medium confidence. Droughts and water scarcity have affected food security in Andean communities, caused human migration, human health issues and loss of hydropower capacity potential.

In summary, our study shows that climate change has already caused glacier retreat, flooding and drought, and this in turn, has caused a cascading of impacts through natural and human systems of the Andes. All these impacts can in large part be attributed to human interference in the climate. These findings highlight the need of understanding complex interactions among systems to further develop adequate adaptation and mitigation strategies.

Abstract ID 640 | Date: 2022-09-12 11:15 – 11:30 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Mackay, Jonathan D (1,2); Barrand, Nicholas E (2); Hannah, David M (2); Potter, Emily (3,4); Montoya, Nilton (5)

The trajectory of glacier mass and meltwater runoff changes in the tropical Andes under 21^st century climate change is likely to be complex due to the combined influence of melt, sublimation and ice flow processes which will bring about highly non-linear responses to rises in near surface air temperature. Results from the Glacier Model Intercomparison Project have shown that simulations of glacier mass changes in the tropics are especially uncertain and highly sensitive to differences in the formulation of fundamental processes including the surface energy balance and ice flow dynamics. Computational and observation data constraints have typically led researchers to employ simplified representations of these processes for the purpose of climate change impact studies. For tropical glaciers, these simplifications have the potential to miss important non-linearities in future glacier mass and runoff changes.

This study presents a physically-based glacier modelling approach that integrates two existing model codes: i) JULES which employs a full surface energy balance model of snow and ice to simulated ice mass changes; and ii) OGGM which employs a flowline representation of the shallow ice equation to simulate ice flow. The integrated approach is applied to over 500 glaciers in the Vilcanota-Urubamba basin in Peru, home to the second-largest tropical glacierised mountain range in the world.

This study first interrogates the simulation efficiency by comparing the model simulations to glaciological and geodetic mass balance data collected in the region. Through sensitivity analysis a process-level assessment of sources of uncertainty is then undertaken. The results from this analysis indicate that overall surface mass balance simulations are good and that the representation of surface albedo dynamics are a key source of uncertainty in simulations. Finally, the model is driven with CMIP5 climate change projections to explore the evolution of mass changes in the region over the 21^st century.

Abstract ID 745 | Date: 2022-09-12 11:30 – 11:45 | Type: Oral Presentation | Place: SOWI – Seminar room U1 |

Mateo, Emilio (1); Mark, Bryan (1); Hellstrom, Robert (2); Baraer, Michel (3); Mckenzie, Jeffrey (4); Condom, Thomas (5)

Glaciers in the high mountains of the Andes greatly contribute to streamflow throughout the year, but in the face of climatic changes, their contributions are fluctuating and becoming less reliable. Our hydrometeorological network in the tropical Andean, Cordillera Blanca, Peru was designed with goals to evaluate how progressive glacier mass loss is impacting stream hydrology, and to better understand the local manifestation of climate change over diurnal to seasonal and inter-annual time scales. Over the past two decades, we have collected high temporal resolution discharge and weather observations in the upper portion of the Rio Santa Watershed, known as the Callejon de Huaylas, spanning across an elevation range of 3700 – 4750 m a.s.l. Analyses of the discharge data at a station in the Quilcayhuanca sub-catchment indicate a steady decrease in cumulative daily discharge during the dry season from 175 m³ to 50 m³, while the wet season discharge fluctuates more but also indicates a decreasing trend from 350 m³ to 150 m³. Daily discharge measurements in the Ranrahirca sub-catchment show an average decline of 1.1 m³/s from the beginning of observations here in 2008, to present. Temperature data gathered along an elevational gradient in the Ranrahirca sub-catchment, indicate increased warming of 0.7 °C/decade at 4500 m a.s.l., in comparison to much a much smaller increase of 0.1 °C/decade at 3900 m a.s.l. The lapse rates attained from this data also indicate a rise in freezing level height from 4800 to 5000 m a.s.l. Warming along this elevational gradient plays a key role in the glacial changes at higher elevations, directly altering the streamflow of rivers at lower elevations.

Abstract ID 840 | Date: 2022-09-12 15:15 – 15:17 | Type: Poster Presentation | Place: SOWI – Garden |

Schoessow, Forrest (1); Shutkin, Tal (1); Mark, Bryan (1); Thompson, Lonnie (1); Lavrentiev, Ivan (2); Kutuzov, Stanislav (2); Cochachin, Alejo (3); Carafice, Chance (1); Howat, Ian (1); Vijay, Saurabh (4); Gómez, Demián (1); Mukherjee, Rohit (5); Huh, Kelly (6); Burns, Patrick (7); Gómez Lopez, Jesús (8)

High-mountain glaciers are the water towers of the tropical Andes and fundamentally important to downstream populations. The greatest concentration of extant tropical glaciers is found in the Cordillera Blanca, Peru, where ice loss has accelerated over recent decades. Past research has revealed that the Rio Santa watershed has passed “peak” discharge, while some sub-catchments with greater ice volume are still building up to peak discharge. Thus, accurate projections of future glacier storage loss provide the critical information to ensure successful water management, inform adaptation strategies, and strengthen community resilience.

Previous continental-to-regional glacier ice thickness and water storage estimates for the Cordillera Blanca range widely between 10-21 Gt. However, a systematic lack of observations above the snowline has hindered efforts to reliably calibrate or validate many of the modeled projections of future changes in glacier mass and meltwater availability. As a result, regional glacio-hydrological projections have relied upon discontinuous and spatially limited measures from more accessible, low-elevation sites to calibrate multiple model parameters, introducing systematic biases tied to over-parameterization and underestimated uncertainties. This complicates the reproducibility of computational studies and confounds decision-making.

Here, we describe an approach to “calibrating the water clock” that systematically addresses these high-altitude, accumulation zone knowledge gaps to improve the parameterization, validation, and output reliability of locally calibrated glacier mass balance, ice thickness, and meltwater runoff models. We examine the extent to which output generated using the flexible Open Global Glacier Model (OGGM) can be enhanced by supplementing and improving upon the minimal input data requirements of the model framework using a combination of direct and remote repeat measures — dGNSS-GPR surveys (ranging 4800-6787 m), airborne lidar, Worldview-derived DEMs, meteorological stations, ice cores, and UAS — compiled in a novel database detailing seasonal to multi-decadal changes in mass balance and morpho-geometric characteristics for individual glaciers across the mountain range. We discuss how a time series approach facilitates stricter chronological alignment of independent input, calibration, and validation datasets, resulting in greater temporal consistency across model boundary conditions. Ouruse of time-synchronous glacier model inputs (e.g. pairing a 2014 GPR survey with a 2014 Worldview stereo DEM instead of 2000 SRTM) is not common practice in mountain regions due to data gaps, but we show how it can improve model output reliability. Finally, we contextualize our locally calibrated model estimates of glacier water storage changes alongside a 33-year observational time series of alpine lake volume fluctuations across the Cordillera Blanca.

Abstract ID 768 | Date: 2022-09-12 15:17 – 15:19 | Type: Poster Presentation | Place: SOWI – Garden |

Beard, Dylan Bodhi (1); Clason, Caroline (1); Rangecroft, Sally (1,2); Rodríguez, Wilmer Sánchez (3); Blake, William (1)

Glaciers have previously been seen as pristine environments. However, research has shown that glaciers can accumulate and store contaminants in cryoconite, an organic-rich sediment found on the surface of glaciers. Numerous anthropogenically and naturally-derived contaminants have been found globally within cryoconite, including fallout radionuclides, potentially toxic elements, and heavy metals. The introduction of these contaminants can come from human activities such as the use of agricultural fertilisers, carbon-based industries, vehicular use, and nuclear power plants. However, these contaminants can also originate from natural sources such as erosion of metal-rich rock and forest fires. Through glacier change, recession, and melting events, these contaminants are remobilized into glacial riverine systems and downstream environments. This can then pose risks to downstream populations who rely heavily on glaciers for meltwater, as well as fragile ecological habitats and ecosystems.

When assessing potential downstream risk from glacial contaminants, it is crucial to know what types of contaminants may be released in meltwaters and in what quantity. Here we identify contaminants within cryoconite from glaciers in Peru’s Cordillera Blanca. Previous studies have shown that glaciers in similar environments (i.e. high mountain glacier catchments) have been found to contain differing types and concentrations of contaminants within cryoconite. However, until now this had not been reported for cryoconite on glaciers in Peru.

This research investigates the variation in contaminant load in cryoconite from four different glaciers (Pastoruri, Shallap, Vallunaraju, and Yanapacca), which all feed into the Rio Santa, Peru. Key contaminants in cryoconite from this region have been quantified and analysed using X-ray fluorescence, gamma spectrometry, and ICP-MS. The bioavailability of these contaminants has also been assessed using a BCR sequential extraction procedure, to determine possible impacts from their release into meltwater. These combined results contribute to an improved understanding of the extent to which glaciers may act as a secondary source of contaminants within the Andes and similar mountainous environments. This is an important first step towards assessing the risk of contaminant release from glaciers in mountain regions.

Abstract ID 701 | Date: 2022-09-12 15:19 – 15:21 | Type: Poster Presentation | Place: SOWI – Garden |

Somos-Valenzuela, Marcelo (1,2); Morales, Bastian (1,3); Lillo, Mario (4); Farias, David (5); Fernandez, Alfonso (5,6); Rivera, Diego (7); Casassa, Gino (8); Huaico, Ana (6); Jaque, Edilia (6); Mark, Bryan (9,10); Xie, Hongjie (11)

The global extension of glaciers peaked in the Holocene by the end of the Little Ice Age, followed by a nearly continuous decline although punctuated by growing periods in some regions. Nowadays, knowing where glaciers are going to shrink faster is uncertain. There are several examples where glaciers of similar size and elevation range within a region respond differently to the same changes in climate. The Karakorum anomaly is one of the most famous examples of this situation. Another example is the Vilcabamba area in Peru, where glaciers are above 5500 m.a.s.l. show higher shrinking rates than glaciers at 5300-5500 m.a.s.l., likely explained by prevalent higher slopes (>45°). Therefore, determining locations where glaciers may remain protected despite significant climatic changes (a concept called “Climate Change Refugia”) becomes essential to support preparedness and adaptation measures. Glaciers of South America are responsible for a significant contribution to sea-level rise (SLR) in the 20th century, with an estimated mass loss of -30.4 ± 13 Gt/yr from 2012 to 2019. Natural hazards associated with glacierized environments in this region are also of concern. The receding glaciers are leaving new glacial lakes, expanding existing glacial lakes, and destabilizing steep hills that can collapse. Additionally, streamflow from small glaciers, which allow maintaining local ecosystems during the summer, are at risk when glaciers’ volume decrease. The mass balance of glaciers depends on two main processes: (1) the thermodynamic mass balance, which is usually used to assess climate change impacts on glaciers or estimate streamflow from glaciers, and (2) glacier shape and subglacial topography, intrinsic characteristics basal shear stress that control downhill movement. We seek to determine characteristics that control the upstream propagation of glacier thinning in Andean glaciers as a response to changes in climate. Thus, this work aims to understand the impact of geomorphometric characteristics, emphasizing the relationship of glacier basal topography and mass balance sensitivity to the present climate. We hypothesize that changes in the glacier terminus propagate upstream constrained by the subglacial topography, for example, the degree of “U” of the subglacial valley, promontories’ size and distribution, elevation concerning sea level, unevenness, and slope. To evaluate this, we will calculate the elevation difference of the Andean glaciers to estimate the loss of ice cover over time. Subsequently, we will estimate the surface mass balance anomaly to determine ablation, allowing us to model the thinning of the glaciers through the diffusive kinematic wave equation.

Abstract ID 314 | Date: 2022-09-12 15:21 – 15:23 | Type: Poster Presentation | Place: SOWI – Garden |

Mcnamara, Gavin (1); Mckenzie, Jeffrey (1); Pomeroy, John (2); Aubrey-Wake, Caroline (2); Fang, Xing (2); Hellstrom, Robert (3); Mark, Bryan (4)

The glaciated valleys of the Andes provide vital freshwater to the arid west coast of South America. The Cordillera Blanca is the largest glacierized region in the tropics, containing 70% of the world’s tropical glaciers with a total glaciated area of 631 km². The warming climate is causing major changes to the Cordillera Blanca; glacial coverage in this region has decreased by 40% since the 1970’s.

Physically based models are useful in comprehending the hydrological processes of remote regions with sparse meteorological data. The Cold Regions Hydrological Model (CRHM) is a flexible, physically based model developed at the Centre for Hydrology, University of Saskatchewan, for improving the understanding of cold regions hydrological processes in poorly gauged or ungauged basins. CRHM includes phenomena specific to cold environments, including snow and ice accumulation, interception, transport and melt, and infiltration through frozen soils.

We use CRHM to simulate the hydrology of the Quilcayhuanca valley, a pampa valley on the western side of the Cordillera Blanca, from July 2014 to July 2018. The model uses a variety of data sources, including satellite imagery, digital elevation models, and weather stations (precipitation, temperature, relative humidity, and wind speed) from the valley floor (Casa de Agua, 3905 m.a.s.l.) and at Cuchillacocha Lake (4625 m.a.s.l.).

The model, divided into 17 hydrologic response units, accurately simulates the discharge recorded at the catchment outflow. Now that the model is able to simulate the bulk hydrology, parameters such as the degree of glaciation, temperature/ precipitation trends, or vegetation type and density can easily be modified to inspect how these catchments may respond to a changing climate. Initial results and comparisons are proving to be successful; there is potential for numerous insights regarding the hydrological responses of glaciated catchments to a dynamic and warming climate.

Abstract ID 170 | Date: 2022-09-12 15:23 – 15:25 | Type: Poster Presentation | Place: SOWI – Garden |

Curry, Charlotte S. (1); Rowan, Ann V. (1); Livingstone, Stephen J. (1); Bryant, Robert G. (1); Quincey, Duncan J. (2); Bravo, Claudio (3); Newton, Andrew M.w. (4)

Glaciers in the Andes were sensitive to localised changes in temperature and precipitation during the Last Glacial and Holocene time periods. However, large research gaps exist between 31°S and 40°S in the arid Chilean Andes. Over anthropogenic time scales, mining for copper, gold and other metals at sites such as Andina and Los Bronces mines present additional complications for understanding glacier evolution. These mines generate large volumes of mineral dust that is deposited on glaciers and affects their surface energy balance by modifying albedo and accelerating melt, and thus the demise of these glaciers. Glacier mass loss will have a detrimental impact on the timing and volume of glacially derived water resources for highly populated downstream areas such as Santiago.

This project aims to assess the impact that mining has had on glaciers between 23° and 40°S in the arid Andes in the context of ongoing Holocene climatic change, to understand glacier change in the past, establish their current volume and recent evolution, and project the future recession and impact for water resources. A combination of geomorphological mapping and 10-Be cosmogenic nuclide exposure-age dating will be used to create a moraine geochronology. This will be used with a glacier model to simulate and evaluate regional glacier evolution through the Holocene across the study region, and project how these glaciers may evolve under a number of different future climate scenarios.

Decadal-scale surface elevation changes between 2000 and present day using ASTER satellite images, and albedo variability between 1972 (start of the Landsat satellite era) and present day for the entire study region will be produced to determine recent glacier change. In addition, we will focus on glacier changes in response to mining activities in the Olivares Basin, where glaciers are approximately 5 km from the Andina and Los Bronces mines. We plan to use a combination of surface reflectance, X-ray diffraction and X-ray fluorescence to determine the distribution and provenance of mine wastes and impact that this dust has had on glacier mass change.