Christian Yarleque

Glaciated areas over the central Andes are highly sensitive to atmospheric forcings, as demonstrated by their current accelerated retreat in response to global warming. The present Thesis is focused on quantifying and assessing future climate change impacts over Quelccaya ice cap (QIC), the world-largest tropical ice body, which is considered as a representative case of the tropical Andean cryosphere. I focused my study on characterizing large-scale forcing and future changes of precipitation and temperature, since they represent the most important variables for accumulation and ablation processes in glaciated mountain regions. In my research I developed tools to overcome the lack of in-situ information over mountain regions; I addressed the challenge to obtain accurate precipitation estimates from coarse-resolution global climate models (GCM), and developed projection of the future state and evolution of the QIC.

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.

The fast retreat of the tropical Andean glaciers (TAGs) is considered an important indicator of climate change impact on the tropics, since the TAGs provide resources to highly vulnerable mountain populations. This study aims to reconstruct the glacier coverage of the TAGs, using Landsat time-series images from 1985 to 2020, by digitally processing and classifying satellite images in the Google Earth Engine platform. We used annual reductions of the Normalized Difference Snow Index (NDSI) and spectral bands to capture the pixels with minimum snow cover. We also implemented temporal and spatial filters to have comparable maps at a multitemporal level and reduce noise and temporal inconsistencies. The results of the multitemporal analysis of this study confirm the recent and dramatic recession of the TAGs in the last three decades, in base to physical and statistical significance. The TAGs reduced from 2429.38 km² to 1409.11 km² between 1990 and 2020, representing a loss of 42% of the total glacier area. In addition, the time-series analysis showed more significant losses at altitudes below 5000 masl, and differentiated changes by slope, latitude, and longitude. We found a more significant percentage loss of glacier areas in countries with less coverage. The multiannual validation showed accuracy values of 92.81%, 96.32%, 90.32%, 97.56%, and 88.54% for the metrics F1 score, accuracy, kappa, precision, and recall, respectively. The results are an essential contribution to understanding the TAGs and guiding policies to mitigate climate change and the potential negative impact of freshwater shortage on the inhabitants and food production in the Andean region.

En el Perú las comunidades localizadas a lo largo de la cordillera de los Andes a más de 3000 metros sobre el nivel del mar tienen un comportamiento altamente susceptible a cualquier tipo de actividad de investigación sobre las áreas de montañas, debido principalmente al mal manejo de las empresas mineras durante muchas décadas, sin un proceso de extracción mineral ecoeficiente u óptimo desde un punto de vista ambiental. El mayor problema que surge al buscar realizar actividades de investigación en dichas áreas consiste en demostrar a las comunidades que las actividades de investigación son de un gran beneficio común y no de intereses particulares. En este artículo se muestran estrategias de trabajos de sensibilización en comunidades de montaña, previos a la ejecución de un proyecto de investigación. Se tomó el caso de estudio el proyecto de instalación de un sistema de monitoreo de la laguna peligrosa de origen glaciar Arhuaycocha, en la subcuenca Río Blanco-Santa Cruz, Áncash, donde el distrito Santa Cruz se ubica en el camino aluviónico. Se realizaron actividades de sensibilización, identificación de actores, análisis situación social y de perspectivas de los pobladores para con el proyecto.Se concluyó que en toda actividad de índole de investigación se debe de realizar con un grado alto de sentimiento de pertenencia por parte de las comunidades, mostrar beneficios directos y lograr acuerdos con las autoridades locales. Un punto clave fue la inclusión de los pobladores en las actividades del proyecto, transparentando y dejando en claro la realización de actividades de ciencia dentro de su comunidad.

Accelerating mountain glacier recession in a warming climate threatens the sustainability of mountain water resources. The extent to which groundwater will provide resilience to these water resources is unknown, in part due to a lack of data and poorly understood interactions between groundwater and surface water. Here we address this knowledge gap by linking climate, glaciers, surface water, and groundwater into an integrated model of the Shullcas Watershed, Peru, in the tropical Andes, the region experiencing the most rapid mountain‐glacier retreat on Earth. For a range of climate scenarios, our model projects that glaciers will disappear by 2100. The loss of glacial meltwater will be buffered by relatively consistent groundwater discharge, which only receives minor recharge (~2%) from glacier melt. However, increasing temperature and associated evapotranspiration, alongside potential decreases in precipitation, will decrease groundwater recharge and streamflow, particularly for the RCP 8.5 emission scenario.

We analyze the future state of Quelccaya Ice Cap (QIC), the world’s largest tropical ice cap with a summit elevation of 5680 m a.s.l., which, in terms of its elevation range (~5300–5680 m a.s.l.), is representative of many low-elevation glacierized sites in the tropical Andes. CMIP5 model projections of air temperature (Ta) at QIC indicate a warming of about 2.4 °C and 5.4 °C (respectively) for RCP4.5 and RCP8.5 scenarios by the end of the 21^stcentury, resulting in a pronounced increase in freezing level height (FLH). The impact of this warming on the QIC was quantified using equilibrium-line altitude (ELA) projections. The change in the ELA was quantified based on an empirical ELA–FLH relationship, and calibrated with observations of the highest annual snowline altitude (SLA) derived from LANDSAT data. Results show that from the mid-2050s onwards, the ELA will be located above the QIC summit in the RCP8.5 scenario. At that time, surface mass balance at QIC and most tropical glaciers at similar elevations will become increasingly negative, leading to their eventual complete disappearance. Our analysis further corroborates that elevation-dependent warming (EDW) contributes significantly to the enhanced warming over the QIC, and that EDW at Quelccaya depends on the rate of anthropogenic forcing.