High up in the Himalaya, it lurks. It is hard to spot with the naked eye. Yet we see the damage it leaves in its wake. No, this is not the elusive Himalayan yeti (though I do have camera traps set out). Rather, I am referring to black carbon or soot – resulting from incomplete combustion of fossil fuels, as well as biofuels and biomass – which deposits on snow and ice in the Himalaya. These dark particles absorb sunlight, warming snow and ice, leading to faster glacier mass loss. These particles are smaller than a strand of hair. Small but mighty, so it seems. Yet, black carbon isn’t the only culprit. Locally and regionally derived dust also can impact snow melt. While dust is a natural occurrence on the planet, recent land use changes, such as road and trail construction can add to the amount. Thus, it is important to consider the combined effect of soot and dust.
As in the Arctic, dark particles on Himalayan snow are a concern as they lead to enhanced heating, melting and sublimation. While melting ice on Greenland can directly contribute to sea level increases, in the Himalaya ice loss affects people on a more local and regional scale – by disrupting water resources, as well as cutting off climbing routes. The Nepalese Himalaya are home to eight of the world’s 8000-meter peaks. As climate continues to change and conditions become more treacherous for climbing, this may affect the local communities who rely on trekkers and mountaineers for income.
From October 2013 – end of May 2014, my team and I collected snow samples across the Khumbu valley in the Everest region (eastern part of Nepal), including Island Peak, Lobuche East, Khumbu glacier, Ngozumpa glacier, Cho La and Renjo La. In central Nepal, we collected samples from Annapurna South and Mt. Himlung in the remote NarPhu valley, on the border with Tibet. Out in the field, the technique is straight-forward: wash your hands (or ice axe) in the snow first, then collect a gallon-size bag of snow from the top few centimeters and the subsurface. The former represents dry deposition from the air while the latter represents deposition in the last snowfall event. You then quickly come back down to camp to melt the samples and run the water through filters, capturing pollutants and other contaminants, which later are analyzed in the lab. The technique I am using was developed by Dr. Carl Schmitt at the National Center for Atmospheric Research, with whom I am collaborating (http://www2.ucar.edu/atmosnews/just-published/8856/measuring-pollutants-andean-glaciers). He developed this while working with the American Climber Science Program throughout the Cordillera Blanca in Peru (http://climberscience.wordpress.com).
Preliminary results show a dominance in relative mass concentration of dust in samples, with particularly high levels of black carbon/dust in more frequented regions such as the high mountain passes and climbing peak high camps. Whodunit? Well, that’s more complicated, but a few suspects are in custody:
- dust from eroding trails at the lower altitudes, due to frequent human and animal traffic during the high trekking seasons in the autumn and spring
- black carbon from wildfires
- soot from yak dung burning stoves in local villages
- dust from road construction in Kathmandu
- black carbon from diesel-belching buses and trucks
- soot from brick factories, though farther geographically, may be carried to the mountains by the wind.
It is clear we are dealing with anthropogenic changes and that needs to be addressed at the local and national government levels. Understanding the sources better and developing mitigation efforts where possible will be key, as well as understanding the effects on the water supply in the region in order to facilitate adaptation.
Acknowledgments Funding for my work includes: National Science Foundation (NSF); USAID; the US Fulbright Program; Geological Society of America (GSA); the Explorers Club; National Snow and Ice Data Center’s (NSIDC) CHARIS project; Rice Space Institute; and individual sponsors/donors through the University of Colorado Boulder and crowd-funding from Petrishdish.org and Rockethub.com.
Team members: Passang Nuru Sherpa, Kami Sherpa, Ang Tendi Sherpa, Nima Sherpa, Dr. John All, Jake St. Pierre, Chris Cosgriff, David Byrne, Marty Coleman, Michael Coote