Current state of glaciers in the tropical Andes: a multi-century perspective on glacier evolution and climate change

Abstract

Abstract. The aim of this paper is to provide the community with a comprehensive overview of the studies of glaciers in the tropical Andes conducted in recent decades leading to the current status of the glaciers in the context of climate change. In terms of changes in surface area and length, we show that the glacier retreat in the tropical Andes over the last three decades is unprecedented since the maximum extension of the Little Ice Age (LIA, mid-17th-early 18th century). In terms of changes in mass balance, although there have been some sporadic gains on several glaciers, we show that the trend has been quite negative over the past 50 yr, with a mean mass balance deficit for glaciers in the tropical Andes that is slightly more negative than the one computed on a global scale. A break point in the trend appeared in the late 1970s with mean annual mass balance per year decreasing from −0.2 m w.e. in the period 1964-1975 to −0.76 m w.e. in the period 1976-2010. In addition, even if glaciers are currently retreating everywhere in the tropical Andes, it should be noted that this is much more pronounced on small glaciers at low altitudes that do not have a permanent accumulation zone, and which could disappear in the coming years/decades. Monthly mass balance measurements performed in Bolivia, Ecuador and Colombia show that variability of the surface temperature of the Pacific Ocean is the main factor governing variability of the mass balance at the decadal timescale. Precipitation did not display a significant trend in the tropical Andes in the 20th century, and consequently cannot explain the glacier recession.Published by Copernicus Publications on behalf of the European Geosciences Union. A. Rabatel et al.: Current state of glaciers in the tropical AndesOn the other hand, temperature increased at a significant rate of 0.10 • C decade −1 in the last 70 yr. The higher frequency of El Niño events and changes in its spatial and temporal occurrence since the late 1970s together with a warming troposphere over the tropical Andes may thus explain much of the recent dramatic shrinkage of glaciers in this part of the world.

Monitoring tropical debris-covered glacier dynamics from high-resolution unmanned aerial vehicle photogrammetry, Cordillera Blanca, Peru

“…Most recently Burns and Nolin (2014) calculated a 25 % reduction in glacier area from 1987 to 2010. Similarly, Racoviteanu et al (2008) calculated a 22.4 % glacier area reduction from 1970 to 2003, during which time the mean glacier terminus elevation increased by 113 m. Glacier changes are altering downstream hydrology, changing water supply in terms of quantity, quality and timing (Baraer et al, 2009(Baraer et al, , 2012Chevallier et al, 2011;Condom et al, 2011;Juen et al, 2007;Kaser et al, 2003;Rabatel et al, 2013). These changes have profound impacts on downstream communities, livelihoods and ecology (Bury et al, 2013(Bury et al, , 2011Carey et al, 2014;Mark et al, 2010;Postigo et al, 2008;Young, 2009Young, , 2014.…”

“…Most recently Emmer et al (2015) combined a single DEM with high-resolution satellite imagery and field investigations to understand the geomorphic evolution and measure surface velocities of the debris-covered Jatunraju Glacier. Most research in the Cordillera Blanca has addressed the entire range with a focus on glacier response to larger-scale climatic perturbations (Rabatel et al, 2013;Vuille et al, 2008) and their role in the hydrologic budget of the Rio Santa basin (Baraer et al, 2012;Juen et al, 2007;Kaser et al, 2010). A number of studies have investigated mass balance response of individual glaciers, though these have generally aggregated mass balance at the glacier scale (Hastenrath and Ames, 1995a, b;Kaser et al, 1990;Winkler et al, 2009).…”

Future climate warming and changes to mountain permafrost in the Bolivian Andes

“…This, along with the relatively homogenous temperature conditions throughout the year in Bolivia (Rabatel et al 2013), justifies the use of the 0°C isotherm as a proxy for permafrost extents in this region. It is these similar summer and winter Fig.…”

“…Overall, Bolivia has a distinctive climate consisting of a dry season (May -August) and a wet season (DecemberFebruary). Temperatures and incident solar radiation are almost homogenous throughout the year, with temperatures 1 or 2°C higher during the wet summer (Rabatel et al 2013).…”

The last 50 years of climate‐induced melting of the Maliy Aktru glacier (Altai Mountains, Russia) revealed in a primary ecological succession

“…In Africa, Kilimanjaro and its vanishing glaciers have become an icon of global warming, attracting broad interest (Kaser, Hardy, Mölg, Bradley, & Hyera, 2004). In South America, the tropical Andes show that the glacier retreat, in terms of changes in surface area and length, over the last three decades is unprecedented since the maximum extension of the Little Ice Age (Rabatel et al., 2013). In North America, airborne laser altimetry has been used to estimate volume changes of 67 glaciers in Alaska from the mid‐1950s to the mid‐1990s and this evidenced that the average rate of thickness change was –0.52 m/year (Arendt, Echelmeyer, Harrison, Lingle, & Valentine, 2002).…”