Simulating Subglacial Hydrology: Insights into the Triggers of Surges and GLOFs

The snowpack and glaciers of the Himalaya-Karakoram range feed several major river systems in Asia which provide water to over one billion people. Glacial retreat, glacial lake outburst flooding (GLOFs), and glacial ice mass balance are all likely strongly affected by subglacial hydrology. Unfortunately, little is known about Himalayan glaciers due to their remoteness and the danger of doing field work there. Recent advances in subglacial hydrological modeling may allow us to shed more light on subglacial processes that lead to changes in ice mass balance and glacial lake flooding. We present the first application of the SHAKTI subglacial hydrology model to a Himalayan glacier. We model the subglacial drainage network of Shishper Glacier, located in Gilgit-Baltistan, Pakistan, to understand its seasonal evolution and history of surges and GLOFs. We find that the modeled seasonal evolution of Shishper's subglacial system follows a similar seasonal pattern to past observed and modeled subglacial systems. Additionally, a central Röthlisberger channel persists through the winter and serves as the basis for the subglacial drainage system throughout the melt season. We also investigate the 2017-2019 surge of Shishper glacier and find that subglacial hydrology, while likely an important component of surging, cannot provide a standalone explanation for surges. This work serves as a nucleus for future modeling work in the Himalayas and provides a new framework for studying the effects of climate change on glacier dynamics, water availability, and glacier-related hazards in the Himalaya-Karakoram (H-K) region.