Pontifical Academy of Sciences
May 10, 2011: Fate of Mountain Glaciers in the Anthropocene (Catholic Climate Covenant)
Glaciers Shrinking Worldwide Threaten Water Supply for Millions
Glacier areas are observed to be shrinking worldwide, with the highest rates at lower elevations. Large glaciers lose their tongues, leaving unstable moraines and fragilely dammed lakes behind, such as Imja Lake in Nepal. Such fragile dams have been subject to failure, causing outburst floods that ravage the already fragile infrastructure of poor communities downstream.
Black Carbon Impact Studied
In Western North America, human disturbance is increasing the dust load from the deserts of the Colorado Plateau and Great Basin, which darkens and thus shortens the snow season in the Colorado Rocky Mountains by 4-7 weeks. The dust particles also add to atmospheric warming by absorbing sunlight. Elsewhere the widespread brown clouds of black carbon from inefficient combustion could have a large impact in regions such as the Himalayas. We have very limited ,and in some cases, no energy and mass balance studies that quantify the black carbon effects on snow and ice in such remote mountain areas. The impacts that we do understand with detailed measurements in the Western North America provide insight into the snow and glacier responses in other similarly affected regions.
Glaciers as Water Towers
The amounts and rates of glacier mass loss differ by region, and so also do the associated impacts on seasonal water availability in close-by valleys and neighbouring lowlands. In regions with dry and warm seasons, such as Central Asia, mountains and their glaciers and winter snows are like water towers that store water for millions of people. Their behaviour can be deceptive. Glacial mass loss can cause an initial temporary increase in runoff downstream from water that has been stored for a long time, as has been observed in several basins, but runoff inevitably decreases as the parent glaciers decrease further. Read More.