Typically, glaciers oscillate between growth and retreat. At the highest elevation, snowfall adds to the glacier's mass. Over several years, this snow compacts into ice, and under its own weight, gravity drags the glacier into a slow drift. At lower elevations, glaciers lose ice by melting and evaporating. If snowfall equals ice melt, the glacier is in equilibrium. Increased philippine phone number lookup snowfall increases a glacier's extent, while increased melting forces glaciers to retreat. However, in this most glaciated part of the world outside the polar regions, some glaciers have not changed, while others have even advanced. Mayer discovered debris blankets, widely present in the Karakoram glaciers, that may be key to their supposed stability.
Natural insulators
“Debris-covered glaciers react very differently to climate change,” Mayer said, “and this needs to be understood.” Unraveling a glacier’s complex role in water supply is crucial for countries like Pakistan, where snow and glacial melt fuel more than 50 percent of the Indus River’s flow, irrigating a heavily agricultural economy.
Area of studyThe image above shows the glacier coverage of the Central Karakoram National Park 2010, obtained during the project (University of Milan, Ardito Desio Institute) and based on the Landsat 2010 satellite. The red line marks the boundary of the study area. The yellow contours represent glaciers analyzed in detail. Photo credit: NASA
Very thin debris — a dark-colored layer on the snow — absorbs more solar energy, leading to faster melting. This is evident in the Rocky Mountains. But in the Karakoram, the debris is much thicker, deposited on the glacier surface by avalanches and rock falls,