Two Decades of Climate Monitoring in Peru’s Cordillera Blanca Reveal El Niño's Role in Elevation-Dependent Warming

Undergraduate Review Volume 19 Article 5 2025 Two Decades of Climate Monitoring in Peru’s Cordillera Blanca Reveal El Niño's Role in Elevation-Dependent Warming Luke Davies Follow this and additional works at: https://vc.bridgew.edu/undergrad_rev Recommended Citation Davies, Luke (2025). Two Decades of Climate Monitoring in Peru’s Cordillera Blanca Reveal El Niño's Role in Elevation-Dependent Warming. Undergraduate Review, 19, 9-29. Available at: https://vc.bridgew.edu/undergrad_rev/vol19/iss1/5 This item is available as part of Virtual Commons, the open-access institutional repository of Bridgewater State University, Bridgewater, Massachusetts. Copyright © 2025 Luke Davies BARTLETT COLLEGE OF SCIENCE AND MATHEMATICS Two Decades of Climate Monitoring in Peru’s Cordillera Blanca Reveal El Niño's Role in Elevation-Dependent Warming Luke Davies Abstract Driven by climate change, elevation-dependent warming (EDW) has become a critical issue in the Cordillera Blanca of Peru. This study focuses on gathering evidence of EDW and determining the relationship between El Niño Southern Oscillation (ENSO) events and micrometeorological forcing in two proglacial valleys. A climate monitoring network was maintained through a 20-year collaboration between Bridgewater State University (BSU), Universidad Nacional Santiago Antúnez de Mayolo (UNASAM), and the Autoridad Nacional de Agua (ANA). Fieldwork in June 2023 and June 2024 included repairing weather stations, installing Lascar sensors, and downloading data loggers to sustain and improve the climate record. Data analysis revealed that El Niño amplifies EDW which raises freezing level heights, hence accelerating glacial melt. These results provide evidence that informs climate resilience and adaptation strategies for mountain communities, particularly concerning water resources. This research acts as a catalyst for expanding efforts to address climate-related disparities in vulnerable and understudied regions globally. 1. Background 1.1 Elevation-Dependent Warming Elevation Dependent Warming (EDW) is a critical aspect of climate change research, particularly in mountain regions where environmental gradients make ecosystems sensitive to variations in temperature. EDW refers to the phenomenon where temperature changes differ with altitude, often resulting in a higher rate of warming at higher elevations compared to lower ones. Understanding this phenomenon is important due to its implications for communities that rely on mountain ecosystems for water resources and agricultural practices. Current theories suggest that EDW is driven by the albedo feedback, resulting from loss of reflective ice and snow at higher elevations with less precipitation falling as snow and melt from “global warming.” Lower albedo causes more absorption of incoming solar radiation. This feedback loop is particularly impactful in regions with seasonal snow and ice cover, such as the Himalayas, the Andes, and the Alps (Pepin et al., 2015). Another theory suggests that water vapor in the air is rising as our atmosphere’s capacity for this greenhouse gas is rising, in addition to a rise in CO2 and other trace gases. Finally, the lapse rate feedback, whereby the slope of the vertical temperature changes with elevation (altitude), can lead to stronger surface warming. The lapse rate becomes shallower (lessens) with greater warming at higher elevations. This process is called the negative lapse rate feedback. In the Cordillera Blanca of Peru, warming has been evident in the retreat of glaciers and changes in seasonal BRIDGEWATER STATE UNIVERSITY | 9 BARTLETT COLLEGE OF SCIENCE AND MATHEMATICS hydrology, which threaten water availability for downstream communities. These shifts are closely linked to temperature increases in high-altitude areas (Vuille et al., 2008). Studies in the Andes and the Rocky Mountains have also reported similar trends, indicating that EDW is a global phenomenon with localized implications for both the environment and human populations (Bradley et al., 2006). As snow and glacial melting accelerate due to increased temperatures at high elevations, water availability in river basins fed by mountain glaciers becomes more variable. This change can lead to alterations in the timing and quantity of water flow, posing risks to agriculture, hydropower generation, and drinking water supplies for communities living downstream (Immerzeel et al., 2010). Biodiversity is also significantly affected by EDW. Mountain ecosystems host a range of species adapted to specific temperature and moisture conditions, with narrow elevation ranges. As temperatures rise, species are forced to migrate upward in search of cooler climates. This leads to habitat loss and increased competition among species. This can have cascading effects on ecological interactions and ecosystem services (Pauli et al., 2012). Additionally, certain plant and animal species may reach the upper limits of their elevation range, facing the risk of "mountaintop extinction" if they are unable to adapt to changing conditions (Körner, 2007). Observational data in many mountain regions is sparse due to the logistical difficulties of maintaining weather stations at high altitudes in challenging terrain. This has led to gaps in long-term climate records, limiting the ability to fully understand historical temperature trends (Pepin et al., 2015). Moreover, the interaction between EDW and regional climate drivers, such as the El Niño-Southern Oscillation (ENSO), adds another layer of complexity. ENSO events can amplify or mitigate temperature changes in mountain regions, creating variabil10 | THE UNDERGRADUATE REVIEW 2025 ity in warming trends that can be difficult to disentangle from other factors (Vuille et al., 2000). 1.2 Peru and its Glaciers Peru is home to some of the most significant tropical glaciers in the world, primarily concentrated in the Andes Mountain range. These glaciers are critical for the region's hydrology, ecosystems, and human communities, providing a source of freshwater to millions of people living in the valleys below. The tropical Andes, spanning from Venezuela to Chile and Argentina, hold 99% of the world’s tropical glaciers, with Peru alone accounting for around 70% of this total (Vuille et al., 2008). The glaciers of Peru act as natural reservoirs, storing water in the form of ice during the wet season and releasing it during the dry season. This glacial meltwater is essential for downstream agriculture, hydropower, and drinking water supplies, especially in the dry season when precipitation is scarce (Vergara et al., 2007). As glaciers shrink, the seasonal variability of water availability increases, leading to more pronounced dry spells during the dry season and a greater likelihood of water scarcity (Buytaert et al., 2017). Moreover, the formation of glacial lakes as glaciers retreat increases the risk of GLOFs, which can cause significant damage to infrastru (...truncated)