27/08/2018

Himalayan glaciers are more prone to changing climate than previously anticipated


A recently published paper in Nature Scientific Reports (Heterogeneity in topographic control on velocities of Western Himalayan glaciers), authored, among others, by Lydia Sam, Anshuman Bhardwaj and Javier Martín-Torres, members of the Group of Atmospheric Science (GAS), has contributed transcendent information about the dynamics of Himalayan glaciers, increasing this way significantly the understanding of this hydro-glaciological system whose monitoring is of the major importance to observe the effects of climate change and to foresee its immediate consequences.

Himalayan glacier
Credit: Karunakar Rayker.

The monitoring of the glaciological systems is a key factor for the assessment of the impacts of climate change on the Earth, both at global and local scales. This is especially important with relation to mountain glaciers which, though representing only the 3% of the global glacial surface, are extremely vulnerable to the increase of mean temperature, and would be the main contributors to sea level rise in case of dramatic melting.

The Hindu Kush-Himalayan glaciers account for approximately 50% of all the glaciers outside the Polar regions, and a population of some 1.3 billion people depends on the hydrological systems they supply, despite which their dynamics are poorly known so far due, among other circumstances, to the lack of glacio-meteorological and glacio-hydrological records from the region. The convenience of going into depth in the understanding of this particular glacial system is urged, in addition, by the fact that the foresee evolution of its glaciers and their hydrology from presently available datasets is alarming and announces a disastrous future for the region.

The new study has overcome the data scarcity and the consequent gaps in the knowledge of these glaciers dynamics by using remote sensing data from satellites, to enquire into the role of certain topographic and geomorphological parameters such as elevation, inclination of the terrain etcetera, in determining the seasonal flow pattern of 112 glaciers in the Baspa River basin.

The velocity of the glaciers’ flow has been inferred from imagery gathered for four years (2013-2017) by Landsat 8 satellite, and then treated by means of Global Land Ice Velocity Extraction (GoLIVE), a dedicated processing system for doing that. As for the geomorphometric parameters, they have been obtained from data recorded by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASPER) instrument, on board Terra satellite, processed afterward with the Global Digital Elevation Model (version 2).

The analysis performed on these data has yielded a depiction of the seasonal behaviour of the glaciers’ flow with regards to geographic and topographic features considered, and has unveiled an intricate dynamics in which the influence of these parameters show significant variability with relation to other factors, such as the elevation or the debris coverage.

Distribution of glaciers at Baspa river basin
Credit: GAS.

Studies of the seasonal and annual patterns of glacier velocities improve our understanding of the ice volume, topography, responses to climate change, and surge events of glaciers. Such studies are especially relevant and equally rare for the Himalayan glaciers, which supply many rivers that sustain some of the most heavily populated mountainous regions in the world. The most prominent inference of the published paper with respect to climate change is the possibility of a polythermal regime for majority of the Himalayan glaciers. In simple words, this means that the glacier movement and thus, their seasonal melting rates equally depend on both, changes in temperatures (which define melting motion) and precipitation events such as snowfall (which aid to deformational movements). Thus, the Himalayan glaciers are not only prone to global warming but they are also expected to show extreme response changing circulation patterns and climate.

Therefore, the paper contributes a quite refined model of the of Himalayan glaciers’ movement regime, allowing to reliably foresee their responses to the future climatic scenarios and, in general, it has raised the need to incorporate dynamic topography in glacio-hydrological models in order to appropriately monitor the constant glacial evolutions.