Abstract
Water resources in many of the world’s arid mountain ranges are threatened by climate change, and in parts of the South American Andes this is exacerbated by glacier recession and population growth. Alternative sources of water, such as more resilient permafrost features (e.g. rock glaciers), are expected to become increasingly important as current warming continues. Assessments of current and future permafrost extent under climate change are not available for the Southern Hemisphere, yet are required to inform decision making over future water supply and climate change adaptation strategies. Here, downscaled model outputs were used to calculate the projected changes in permafrost extent for a first-order assessment of an example region, the Bolivian Andes. Using the 0 °C mean annual air temperature as a proxy for permafrost extent, these projections show that permafrost areas will shrink from present day extent by up to 95 % under warming projected for the 2050s and by 99 % for the 2080s (under the IPCC A1B scenario, given equilibrium conditions). Using active rock glaciers as a proxy for the lower limit of permafrost extent, we also estimate that projected temperature changes would drive a near total loss of currently active rock glaciers in this region by the end of the century. In conjunction with glacier recession, a loss of permafrost extent of this magnitude represents a water security problem for the latter part of the 21st century, and it is likely that this will have negative effects on one of South America’s fastest growing cities (La Paz), with similar implications for other arid mountain regions.
Highlights
Water security in many arid mountain regions is under threat from climate change, glacier recession and population growth (Viviroli et al 2011; Buytaert and De Bièvre 2012)
Our study examines the likely effect of climate change on active rock glaciers, which are a useful indicator of the lower boundary of mountain permafrost (Barsch 1996)
Levels of warming projected for the Bolivian Andes were at the higher end of these ranges, with projections suggesting a 2.7–3.2 °C increase by the 2050s and 4.2–4.9 °C by the 2080s (Fig. 1b,c)
Summary
Water security in many arid mountain regions is under threat from climate change, glacier recession and population growth (Viviroli et al 2011; Buytaert and De Bièvre 2012). Continued warming is expected to cause further retreat and degradation of highelevation permafrost (Haeberli et al 1993) It is “virtually certain” that Northern Hemisphere permafrost will continue to decline during the 21st century (IPCC 2013, p.1032), similar predictions for Southern Hemisphere permafrost are not available. This represents a substantial knowledge gap, in regions where water security is already at risk. We address this gap by providing a first-order assessment of the impact of climate change on mountain permafrost in the Bolivian Andes. We have used the Bolivian Andes as an example of an arid high mountain system to explore the vulnerability of these water stores to future climatic change, and to highlight the climate change adaptation issues that follow
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