Current And Future Glacier Vanishing And Associated Lake Growth In The Peruvian Andes

Worldwide, climate change and associated glacier shrinkage is a common concern, as it affects, among other things, mountain communities, tourism, and downstream water supplies. Despite this mounting concern, long-term impacts of vanishing ice on river discharge and lake changes, particularly for the next decades, are not well understood or explored.

Figure 1: Potential future glaciers (2050: turquoise area, 2100: light blue area) and future lakes (dark blue areas) in the Cordillera Vilcanota, Southern Peru). Background imagery: Google Earth.

A recent study in the Andes of Peru has now combined knowledge about current glacier and lake trends with possible future scenarios until the end of this century. For the study, researchers selected the Vilcanota-Urubamba basin in Southern Peru (Cusco), one of the most extensively glaciated areas in Peru and the tropical glacier regions worldwide. This basin is characterized by traditional livelihoods (peasant communities, Quechua-speaking) as well as increasing water demand driven by population growth, (irrigated) agriculture, and tourism, which also includes the Inca citadel of Machu Picchu.

Data derived from freely-available satellite imagery of Landsat 5 and Sentinel-2 including digital terrain information from SRTM Alos Palsar has been combined with the Glacier bed Topography (GlabTop) model in order to model potential sites of future lakes and estimate the future glacier extent. Therefore, climate model data from the Coupled Model Intercomparison Project Phase 5 (CMIP5) and Representative Concentration Pathway (RCP) scenarios of the Intergovernmental Panel on Climate Change (IPCC) have been used.

Figure 2: New lake (background) in the Cordillera Vilcanota. Credit: Fabian Drenkhan

The combined analysis shows that the glacier area has been reduced by around 37% (~84 km²) since 1988, which corresponds to a total loss of 21% (~1.7 km³) of ice volume. In this period, 84 new lakes have developed in areas of vanishing glaciers with an increase of 3.6 km² in lake area and 62 million m³ in estimated lake volume. It is important to mention in this context that both glacier shrinkage and lake development are subject to high variability. While ice loss was more pronounced in the lower-lying Urubamba and Vilcabamba glaciers in the northwest, most lakes developed in the wide and flat topography of the Cordillera Vilcanota in the southeast of the basin.

The presented paper shows that future glacier areas could substantially decrease depending on the emission scenarios and associated warming trends in the Andes. For the low-emission scenario RCP2.6, about 40% (from current levels) would be reduced until the end of this century. In contrast, under conditions of the high-emission scenario RCP8.5, more than 90% of all glacier extent would have disappeared until 2100. At the same time, several new lakes with important water storage volume would develop at elevations between ~4900 and 5300 m asl.

Figure 3: Abundant vegetation around Cordillera Urubamba. Credit: Fabian Drenkhan

These findings show that, depending on the scenario, future Andean landscapes might be characterized by mostly glacier-free areas, including several new lakes. With ongoing glacier shrinkage on steep mountain slopes and thawing permafrost, these lakes might be subject to increasing outburst flood potentials which would put at risk downstream communities and assets. On the other hand, the new and growing lakes represent important options for water management, particularly in the context of vanishing glaciers, increasing water demand and, generally, a pronounced dry season in the region.

The study shows, that under the scenarios of change – as glacier shrinkage is continuing – feasible water management and storage options in the region now have to be explored and implemented. Nonetheless, robust adaptation in Peru and the Andean region is tempered with high uncertainties, due to data inconsistencies, reduced process understanding, and complex hydroclimatic and socioenvironmental intertwining. Future efforts in the region must be planned and implemented in close collaboration with local and regional decision-makers at the interface of science and policy.

Figure 4: Indigenous people in the Vilcanota region. Credit: Fabian Drenkhan

These findings are described in the article entitled Current and future glacier and lake assessment in the deglaciating Vilcanota- Urubamba basin, Peruvian Andes, recently published in the journal Global and Planetary Change. This work was conducted by Fabian Drenkhan, Lucía Guardamino, Christian Huggel and Holger Frey from the University of Zurich, Switzerland and the Pontifical Catholic University of Peru.

Reference:

1. Drenkhan, F., Guardamino, L., Huggel, C. and Frey, H. (2018): Current and future glacier and lake assessment in the deglaciating Vilcanota-Urubamba basin, Peruvian Andes. Global and Planetary Change, 169, pp. 105–118. https://doi.org/10.1016/j.gloplacha.2018.07.005

For further reading:

1. Colonia, D., Torres, J., Haeberli, W., Schauwecker, S., Braendle, E., Giraldez, C. and Cochachin, A. (2017): Compiling an Inventory of Glacier-Bed Overdeepenings and Potential New Lakes in De-Glaciating Areas of the Peruvian Andes: Approach, First Results, and Perspectives for Adaptation to Climate Change. Water, 9, pp. 1–18. https://doi.org/10.3390/w9050336
2. Glacier Project (2018): Brief: Modelling future lakes in glaciers beds. 6 pp. Lima, Peru. Online: http://www.proyectoglaciares.pe/wp-content/uploads/2018/06/Brief-Modelling-future-lakes-in-glacier-beds.pdf
3. Glacier Project (2018): Brief: Variables and factors to be taken into account in the analysis of future climate. 6 pp. Lima, Peru. Online: http://www.proyectoglaciares.pe/wp-content/uploads/2018/05/Brief-Variables-and-factors-to-be-taken-into-account-in-the-analysis-of-future-climate-1.pdf
4. Paul, F. and Linsbauer, A. (2012): Modeling of glacier bed topography from glacier outlines, central branch lines, and a DEM. Int. J. Geogr. Inf. Sci., 26, pp. 1–18. https://doi.org/10.1080/13658816.2011.627859
5. Schauwecker, S., Rohrer, M., Huggel, C., Endries, J., Montoya, N., Neukom, R., Perry, B., Salzmann, N., Schwarb, M. and Suarez, W. (2017): The freezing level in the tropical Andes, Peru: an indicator for present and future glacier extents. J. Geophys. Res. Atmos., 122, pp. 1–18. https://doi.org/10.1002/2016JD025943