20TH CENTURY CLIMATE CHANGE IN THE TROPICAL ANDES: OBSERVATIONS AND MODEL RESULTS (original) (raw)
Related papers
The Cryosphere, 2013
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. 82 A. Rabatel et al.: Current state of glaciers in the tropical Andes On 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.
Journal of Geophysical Research, 2003
1] The reasons for the accelerated glacier retreat observed since the early 1980s in the tropical Andes are analyzed based on the well-documented Chacaltaya glacier (Bolivia). Monthly mass balance measurements available over the entire 1991-2001 decade are interpreted in the light of a recent energy balance study performed on nearby Zongo glacier and further put into a larger-scale context by analyzing the relationship with oceanatmosphere dynamics over the tropical Pacific-South American domain. The strong interannual variability observed in the mass balance is mainly dependent on variations in ablation rates during the austral summer months, in particular during DJF. Since high humidity levels during the summer allow melting to be distinctly predominant over sublimation, net all-wave radiation, via albedo and incoming long-wave radiation, is the main factor that governs ablation. Albedo depends on snowfall and a deficit during the transition period and in the core of the wet season (DJF) maintains low albedo surfaces of bare ice, which in turn leads to enhanced absorption of solar radiation and thus to increased melt rates. On a larger spatial scale, interannual glacier evolution is predominantly controlled by sea surface temperature anomalies (SSTA) in the eastern equatorial Pacific (Niño 1+2 region). The glacier mass balance is influenced by tropical Pacific SSTA primarily through changes in precipitation, which is significantly reduced during El Niño events. The more frequent occurrence of El Niño events and changes in the characteristics of its evolution, combined with an increase of near-surface temperature in the Andes, are identified as the main factors responsible for the accelerated retreat of Chacaltaya glacier. Citation: Francou, B., M. Vuille, P. Wagnon, J. Mendoza, and J.-E. Sicart, Tropical climate change recorded by a glacier in the central Andes during the last decades of the twentieth century: Chacaltaya, Bolivia, 16°S,
The Tropical Andes shelter almost all the glaciers in the low latitudes. Glaciers in this region directly feed key water basins that supply big cities with water for consumption and other purposes. Scientific publications have performed mass balance and geometry-length analysis with available recorded data for three glaciers: Chacaltaya in Bolivia, Antisana in Ecuador and glaciers in the Cordillera Blanca in Peru. An accelerated recession of the glaciers is mentioned in all the cases since the early 1980s as a response of the high sensitivity of this region to the increase in the mean temperature of the planet and the ENSO variability effect over temperature and precipitation. The retreat in the Tropical Andes Glaciers have a decisive influence over runoff behaviors that result on initial peaks of water flows into rivers, risking later buffering in the dry season due to glacier depletion.
Glacier monitoring and glacier-climate interactions in the tropical Andes: A review
Journal of South American Earth Sciences, 2017
Chevallier et al., 2011; Gascoin et al., 2011). Many of the catchments of the Cordillera Blanca are glacially fed (Juen et al., 2007; Baraer et al., 2015). Runoff from basins near the rapidly retreating glaciers would be high in the beginning, then decreases and finally declines. Recently, Soruco et al. (2015) observed that runoff in La Paz city in Bolivia is sustained by increased melt rates, where nearly 15% of the annual water resources (14% in the wet season and 27% in the dry season) are contributed by glaciers. They estimated, with Rabatel et al. (2006), based on mean ELA variations, reconstructed the glacier recession on Cerro Charquini in the central Andes, Bolivia between the Little Ice Age (LIA) and 1997. It is possible to calculate ELA of tropical Andean glaciers (or alpine glaciers in general) on millennial timescale using statistical approaches (Seltzer, 1994). Interpreting climate of the past based on the variations in glacier length or ELA, even though a complete record is not available, is commonly used during the last few decades (Benn et al., 2005; Jomelli et al., the austral winter) is found in the outer tropics (Rabatel et al., 2013) and this makes this region somewhat similar to the subtropics. In other words, in the outer tropics, the climate conditions are tropical only during the wet austral summer (Kaser and Osmaston, 2002) and subtropical conditions prevail during the dry austral winter whereas permanently humid conditions prevail in the inner tropics. model, Journal of Geophysical Research 107(D8), 4061.
The Cryosphere, 2013
The role of glaciers as temporal water reservoirs is particularly pronounced in the (outer) tropics because of the very distinct wet/dry seasons. Rapid glacier retreat caused by climatic changes is thus a major concern, and decision makers demand urgently for regional/local glacier evolution trends, ice mass estimates and runoff assessments. However, in remote mountain areas, spatial and temporal data coverage is typically very scarce and this is further complicated by a high spatial and temporal variability in regions with complex topography. Here, we present an approach on how to deal with these constraints. For the Cordillera Vilcanota (southern Peruvian Andes), which is the second largest glacierized cordillera in Peru (after the Cordillera Blanca) and also comprises the Quelccaya Ice Cap, we assimilate a comprehensive multi-decadal collection of available glacier and climate data from multiple sources (satellite images, meteorological station data and climate reanalysis), and analyze them for respective changes in glacier area and volume and related trends in air temperature, precipitation and in a more general manner for specific humidity. While we found only marginal glacier changes between 1962 and 1985, there has been a massive ice loss since 1985 (about 30 % of area and about 45 % of volume). These high numbers corroborate studies from other glacierized cordilleras in Peru. The climate data show overall a moderate increase in air temperature, mostly weak and not significant trends for precipitation sums and probably cannot in full explain the observed substantial ice loss. Therefore, the likely increase of specific humidity in the upper troposphere, where the glaciers are located, is further discussed and we conclude that it played a major role in the observed massive ice loss of the Cordillera Vilcanota over the past decades.
Anais XVII Simpósio Brasileiro de Sensoriamento Remoto, 2015
This paper describes the application of remote sensing for the estimation of the snowline equilibrium altitudes of mountain glaciers in the outer tropics and the use of snowline altitudes as a valuable approximation of the equilibrium line altitude of the year and hence to get the most proximal estimation of annual mass balance changes. In this case study, we used the images from Landsat series – MSS, TM, ETM+ and Landsat 8 - images of the Nevado Sajama in the Western Cordillera in Bolivia. Snowline altitude of a selected outlet glacier of the study site for each year during the dry season was calculated and the maximum snowline calculated during the dry season can be taken as the equilibrium line altitude of the year. Anomalies in precipitation and air temperature were calculated and compared with the observed differences in the calculated annual snowline changes. We also considered three ocean-atmospheric oscillations in the Pacific – ENSO, PDO and AAO. It is found that the snowline altitude of this mountain glacier have been fluctuated with the cold and warm regimes of ENSO and PDO. It is hypothesized that the retreat of this mountain glacier in the Western Cordillera is not as rapid as the Eastern Cordillera in the outer tropics, probably due to the cold regimes of PDO and high altitude of the Nevado Sajama retards the rapid ablation in this region.
AMBIO: A Journal of the Human Environment, 2000
In ablation areas, mass balance has been surveyed on a monthly scale, providing interesting details about the seasonal pattern in 2 contrasting tropical environments. Intermittent information about ice recession exists in both regions for the last 4 decades. The data point to a clear acceleration in glacier decline during this decade; ablation rates have been 3-5 times higher than during the former decades. Fluctuations measured before on 3 glaciers in northern Peru, allow the assumption that the rate at which the glaciers retreated in the tropical Andes increased in the late 1970s. The present situation is particularly dramatic for the small-sized glaciers (< 1 km') and many such as Chacaltaya, could disappear in the next 10 years. As evidenced by the data collected, ablation increases significantly during the warm phases of ENS0 (EI Niño) and decreases during the cold phases (La Niña). Warm events becoming more frequent and intense since the late 197Os, it can be assumed that they have played an important role in the recent glacier decline in the central Andes, together with the global warming. 10 "N
AMBIO: A Journal of the Human Environment, 2000
In ablation areas, mass balance has been surveyed on a monthly scale, providing interesting details about the seasonal pattern in 2 contrasting tropical environments. Intermittent information about ice recession exists in both regions for the last 4 decades. The data point to a clear acceleration in glacier decline during this decade; ablation rates have been 3-5 times higher than during the former decades. Fluctuations measured before on 3 glaciers in northern Peru, allow the assumption that the rate at which the glaciers retreated in the tropical Andes increased in the late 1970s. The present situation is particularly dramatic for the small-sized glaciers (< 1 km') and many such as Chacaltaya, could disappear in the next 10 years. As evidenced by the data collected, ablation increases significantly during the warm phases of ENS0 (EI Niño) and decreases during the cold phases (La Niña). Warm events becoming more frequent and intense since the late 197Os, it can be assumed that they have played an important role in the recent glacier decline in the central Andes, together with the global warming. 10 "N