Himalayan snow and ice is diminishing fast. Global heating is certainly playing a significant role, but now a recent study in Nature Climate Change reveals that wind-blown dust is worsening the melting effect.
Winter snowfall and spring snowmelt provide more than half of the annual freshwater needs of around 700 million people in south Asia, but over the last 30 years the overall snow mass on the high mountains of Asia, which include the Himalayas, the Hindu Kush and the Karakoram, has decreased.
Yun Qian, from the Pacific Northwest National Laboratory, and colleagues used remote sensing observations and computer simulations to assess the impact of dust blowing in from Africa and Asia during spring and summer. The darkening effect of dust reduces the reflectivity of snow, making it melt faster than pristine snow.
Qian and colleagues found that dust darkening significantly enhanced melting and was particularly pronounced at about 4,500 metres. Although the dust is natural, human activities have increased its prevalence, with changing land-use releasing more dust from the land, while increasing temperatures have altered atmospheric circulation patterns. The scientists were surprised by how dominant the dust effect was, and they speculate that dust-induced melt may play a major role on other mid-latitude mountain ranges too.
