Climate change melting glaciers in the Andes – ‘They will probably completely disappear within the coming decades’Posted by Jim at Wednesday, January 23, 2013
By Jeremy Hance
22 January 2013
(mongabay.com) – Glaciers are melting faster than ever in the tropical Andes, warns a new study published in The Cryosphere, which puts the blame for vanishing glaciers squarely on climate change. The study — the most comprehensive to date — found that since the 1970s glacier melt in the region has been speeding up, threatening freshwater supplies in Peru and Bolivia.
"The ongoing recession of Andean glaciers will become increasingly problematic for regions depending on water resources supplied by glacierised mountain catchments, particularly in Peru," the scientists write. They note that freshwater supplies in Peru's Santa River Valley as well as in Bolivia's capital city, La Paz, will likely be imperiled as glaciers vanish.
The scientists looked at precipitation changes over the last century in the region, but found that it could not explain the current melting, which they describe as "unprecedented." Instead the glaciers are melting due to rising temperatures from climate change: regional temperatures have jumped by 0.7 degrees Celsius (1.26 degrees Fahrenheit) during the last fifty years.
Not surprisingly, the scientists say that small, low-altitude glaciers are currently most at risk of disappearing as temperatures rise.
"Because the maximum thickness of these small, low-altitude glaciers rarely exceeds 40 metres, with such an annual loss they will probably completely disappear within the coming decades," said lead author Antoine Rabatel, researcher at the Laboratory for Glaciology and Environmental Geophysics in France. [more]
ABSTRACT: 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.
(BBC) – Glaciers in the tropical Andes have shrunk by an average of 30-50% since the 1970s, according to a study.
The glaciers, which provide fresh water for tens of millions in South America, are retreating at their fastest rate in the past 300 years.
The study included data on about half of all Andean glaciers and blamed the melting on an average temperature rise of 0.7C from 1950-1994.
Details appear in the academic journal The Cryosphere.
The authors report that glaciers are retreating everywhere in the tropical Andes, but the melting is more pronounced for small glaciers at low altitudes.
Glaciers at altitudes below 5,400m have lost about 1.35m in ice thickness per year since the late 1970s, twice the rate of the larger, high-altitude glaciers.
The researchers also say there was little change in the amount of rainfall in the region over the last few decades and so could not account for changes in glacier retreat.
Without changes in rainfall, the region could face water shortages in the future, the scientists say.
The Santa River valley in Peru could be most affected; its hundreds of thousands of inhabitants rely heavily on glacier water for agriculture, domestic consumption, and hydropower.
Large cities, such as La Paz in Bolivia, could also face problems. "Glaciers provide about 15% of the La Paz water supply throughout the year, increasing to about 27% during the dry season," said co-author Alvaro Soruco from the Institute of Geological and Environmental Investigations in Bolivia. [more]