Andean glaciers and their role in the high mountain water cycle

Abstract/Description

Global warming exacerbates water scarcity by increasing the frequency of hydrological droughts. These droughts can be buffered by glaciers, which mitigate runoff variability across multiple timescales. However, as glaciers retreat, the reliability of this unique natural water reserve becomes increasingly uncertain, potentially intensifying drought stress. While the fields of hydrological modelling and glacier change modelling have advanced considerably, they are often treated independently, resulting in high levels of uncertainty. To address this, we leverage recent advances in regional and global datasets and propose a hybrid modelling approach that combines Long Short-Term Memory (LSTM) neural networks with process-based glacier modelling. Unlike traditional glacio-hydrological models that require parameterisations and basin-specific calibration, the proposed approach can leverage data-driven relationships between meteorological inputs, basin characteristics, and streamflow. We present a proof of concept in the Andes that examines the role of glaciers in the propagation of meteorological to streamflow drought. Furthermore, we explore potential changes in this influence by employing “what-if” storyline scenarios that incorporate projected glacier states. Our hybrid modelling approach improves the representation of the complex interactions between glacier dynamics and streamflow droughts. Preliminary results indicate that glaciers play a crucial role in buffering streamflow droughts, delaying and reducing drought severity under historical climate conditions. However, under “what-if” storyline scenarios, this buffering capacity declines considerably, leading to more frequent and prolonged drought events. The storyline-based analysis further suggests that the most pronounced changes occur in basins with a high dependency on glacier meltwater, particularly in arid regions. The results underscore the potential of hybrid modelling in enhancing our understanding of glacier-drought interactions, offering valuable insights for climate change communication and informing adaptation strategies in high mountain regions such as the Andes.

Abstract/Description

Andean tropical glaciers are important indicators of climate change, provide freshwater resources for downstream communities, and form an important component of the hydrological cycle, supporting some 90 million people. Today, with highly seasonal precipitation and drought, Andean glacier ice, snow, wetlands (bofedales) and lakes play a crucial role in delaying water release, sustaining baseflows and water quality. Glacier shrinkage and changing precipitation patterns and water availability here impacts both high Andean pastoralist systems and other, downstream productive systems, including bigger cities in the inter-Andean valleys. Here we outline the hydrological and geomorphological relationships between glaciers, high-altitude wetlands and downstream hydrology in the Cordillera Vilcanota, Cuzco region, Peru. We present a new geomorphological map of glacial and hydrological features within the Vilcanota catchment. Across this domain we mapped ~23,000 features across seven key landform assemblages: topographic, glacier, subglacial, ice-marginal, fluvial, lacustrine and paraglacial. Our reconstructed maximum icefield covers 2660 km2 and was drained by 11 topographically constrained ice lobes across the region. Our geomorphic mapping reveals seven clear ice margins, morphostratigraphically correlated across the study region, reflecting at least seven palaeoglacier advances during the last glacial cycle, Late Glacial period and the Holocene. Understanding the dynamics and patterns of behaviour of tropical palaeoglaciers is important for interpreting their sensitivities and vulnerabilities. Furthermore, we investigate the way in which the mapped geomorphic features such as moraines, talus slopes and sandar interact with catchment hydrology and impact hydrogeological processes. Bofedales are well developed within glacial limits, with glacial processes such as erosion and formation of moraines providing the poorly drained conditions suitable for their development. The majority of the bofedales are largely hydrologically independent of contemporary glaciers, and could partially buffer water supplies as glaciers dwindle and disappear. This analysis enables an improved understanding of the timeframe for the formation of bofedal wetlands and for them to provide their key ecosystem services of water retention capacity, buffering drought, providing forage for high-Andean livestock herding, carbon storing and sequestration. These insights have implications for the

Abstract/Description

Tropical glaciers are essential for water security and energy generation in the Vilcanota Mountain Range, the second-largest glaciated range in Peru. This study aims to determine the future fluctuations in the climatic equilibrium line altitude (CELA) in five sectors of the Vilcanota Mountain Range: Ausangate, Quelccaya, Quisoquipina, Japu Punta, and Osjollo Anante (Chumpe), identified as glacier zones particularly sensitive to climate change. Climate data from WorldClim (WC) and CHELSA (CH) were validated for the reference period, and their spatial resolution was enhanced through statistical downscaling using the Geographically Weighted Regression (GWR) method for both the reference period and future scenarios. Using the high-resolution climate data obtained, the CELA was estimated considering mean air temperature and mean annual precipitation as the main variables. When compared with observed data, the WC climate data showed a higher correlation than CH, as well as a lower root mean square error (RMSE) and percentage bias (PBIAS) compared to CH climate data. Future scenarios were projected for 2030, 2050, and 2090 using seven global climate models from CMIP6 under different socioeconomic pathways (ssp1-2.6, ssp3-7.0, and ssp5-8.5). The results indicate that by the mid-21st century, the CELA would surpass the summit of the Quelccaya and Quisoquipina glaciers, highlighting the high vulnerability of these resources to climate change and its potential impacts on water availability and associated ecosystems.

Abstract/Description

Glaciers across the Andes are presently losing mass, with projections showing this is set to continue into the future. But the degree of glacier mass loss into the future still remains uncertain. Mass loss is thought to be partly associated with a decrease in snowfall at higher elevations in response to a warming climate. Understanding this potential reduction in snowfall at present, and into the future, is therefore important as it will affect the stability of these glaciers, and can enable more robust estimates of future glacier mass changes. However, the ability of the modelling studies to fully understand this change is restricted by the limited snowfall measurements that could be used to calibrate predictive models, as well as the insufficient model representation of changing climate drivers of mass loss across this region.

Here, as part of the Deplete and Retreat: The Future of Andean Water Towers project, we investigate the evolution of the snowpack and glacier mass balance across glaciers in the Cordillera Vilcanota in the tropical Andes. We aim to address this by using COSIPY, a coupled snowpack and ice surface energy mass balance model to investigate the evolution of the snowpack and glacier mass balance across this region in a series of intervals from 2000 to 2150 CE. The model was run at 100 m horizontal resolution and forced by results from the convection-permitting (4 km resolution) regional climate model WRF (Weather Research Forecasting, version 4.6) simulations. The COSIPY runs will be tested against observations of snowline extent and thickness from remote sensing data and automated weather stations respectively, from 2000-2024 to ensure the seasonal variations in the snowpack are captured. The projections into the future will be of vital importance to understand future hydrological and glaciological changes, and will be used to predict changes in snow cover into the future.