Recent research has provided valuable information on glacier processes in the Hindu Kush Himalaya (HKH) mountains of South Asia, a region often called the “Third Pole” because it contains the largest area of ice outside the Arctic and Antarctic. Glacier retreat in this region has attracted considerable scientific and media attention. The 2007 Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) stated that Himalayan glaciers were shrinking faster than those in other parts of the world, and would likely be gone by the year 2035. This comment became controversial in 2009 because of its inaccuracy and weak basis in scientific research, and because glacier retreat in this region has major consequences for water supplies in one of the most densely-populated regions of the world. The IPCC made subsequent corrections in 2010.
This video from 2010, ‘Himalayan Glaciers Melting Faster Than Anywhere Else in World,’ conveys the tone of concern during the period of the controversy.
Stemming from this controversy, documenting the glacier coverage in the HKH has become a topic of critical importance. A recent study by Bajracharya et al. (2015) helps establish the extent of glacier coverage in the HKH region and the rate of glacier change in several basins in this region.
The rugged topography and the poor road networks in the HKH region have limited ground-based data collection. Remote sensing is therefore an attractive alternative. Bajracharya, a researcher at ICIMOD in Kathmandu, and his colleagues utilized satellite images, combining them in some cases with available ground-based data.
The study maps glacial coverage and retreat for a period extending from about 1980 (the precise date varies from location to location) through 2010. They map the decadal glacial change for the 1980s, 1990s and 2000s for four large representative basins which span the HKH region from west to east. The study basins are the Wakhan Corridor in Afghanistan, the Shyok Basin in Pakistan, the Imja Valley in Nepal, and the Lunana region in Bhutan. Glacier melt is a critical source of drinking and irrigation water for large populations in the regiona and critical to hydropower generation as well; glacial processes are also important because of the associated risks of glacier lake outburst floods (recap Imja Lake in Nepal).
So what can be learned from these newly assembled and analyzed data? First, the study reports, that despite the importance of glaciers in the HKH region, they cover only 1.4% of the region. In addition, it finds that glacier retreat is proceeding at different rates in different places. The most rapidly retreating glaciers are the ones located below 5000 m above sea level and the ones that are smallest in area. Combining these factors, the most impacted basin in the study is the Wakhan Corridor in Afghanistan.
The contributions of this study notwithstanding, scientific challenges in the HKH remain. The researchers note that there is continued uncertainty about glacier retreat and downstream impacts, because of uncertainties about future climate change and about the responses of glaciers to this change in this region, for which research remains incomplete. This study sets the stage for future research, looking to past data and suggesting directions of future work.
This prize-winning video from UNDP, the ‘Himalayan Meltdown,’ provides a thorough overview of the region and shows the need for ongoing research.