August 26, 2019 - Tibetan Plateau

Popcorn clouds and snowcaps on the highest mountain peaks dotted the “Roof of the World” in mid-August 2019. The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of the Tibetan Plateau on August 14. The Himalaya Mountains sit south of this high-altitude plateau.

The Tibetan Plateau is home to more than 1,500 large and small lakes that cover 24,183 square kilometers (9,337 square miles). The area is also the source of many of Asia’s major rivers, including the Brahmaputra, Indus, Ganges, Salween (Nu Jiang), Mekong (Lancang Jiang), Yangtze (Chang Jiang), and Yellow (Huang He) Rivers. In this image, sapphire lakes dot the plateau’s rugged surface. Most of these lakes are fed by the winter snow-melt from the snow that encrusts this region in the winter, as well as from glacial melt in the Himalayan Mountains.

As the climate warms, Himalayan glacial melt is picking up speed—and bringing some unexpected consequences. A study published in the June 2019 AGU Journal of Geophysical Research Atmospheres finds that chemicals used in pesticides that have been accumulating in glaciers and ice sheets since the 1940s are being released as Himalayan glaciers melt as a result of climate change. According to the authors, the Himalayan glaciers contain even higher levels of atmospheric pollutants than glaciers in other parts of the world because of their proximity to south Asian countries that are some of the most polluted regions of the world. The study measured concentrations of a class of chemicals used in pesticides called perfluoroalkyl acids (PFAAs) in glacial ice and snow, meltwater runoff, rain and lake water in Nam Co Basin. The tests performed on ice, snow, and water samples showed that glaciers in the region are releasing around 1,342 milligrams of PFAAs per day into Lake Nam Co. They detected levels as high as 2,171 picograms per liter in the lake. Under these conditions, the estimated total annual input of PFAAs into Lake Nam Co is approximately 1.81 kilograms per year. PFAAs are known for having a very long lifespan. These chemicals don’t biodegrade easily and are readily passed through organisms and ecosystems, while being continually concentrated through various biogeochemical processes. The resulting levels of chemical pollutants can have impact on life in the lake, and bioaccumulation in fish may result in problems in people who eat the fish. The Nam Co water basin feeds directly into the water resources of India.

Image Facts
Satellite: Terra
Date Acquired: 8/14/2019
Resolutions: 1km (292.4 KB), 500m (793.6 KB), 250m (568.6 KB)
Bands Used: 1,4,3
Image Credit: MODIS Land Rapid Response Team, NASA GSFC