Simulating seasonal evolution of subglacial hydrology at a surging glacier in the Karakoram

Abstract Glacier motion, retreat and glacier hazards such as surges and glacial lake outburst floods (GLOFs) are likely underpinned by subglacial hydrology. Recent advances in subglacial hydrological modeling allow us to shed light on subglacial processes that lead to changes in ice mass balance in High Mountain Asia. We present the first application of the Subglacial Hydrology And Kinetic, Transient Interactions (SHAKTI) model on an alpine glacier. Shishper Glacier, our study site, is a mountain glacier in northern Pakistan that exhibits concurrent surges and GLOFs, which endanger local communities and infrastructure. Without coupling to ice velocity, the modeled subglacial hydrological system undergoes transitions between inefficient to efficient drainage and back during spring and fall, supporting previous observations of spring and fall speedups of glaciers in the region. We compare modeled effective pressures from the years 2017-19 with previously observed velocities, suggesting that while subglacial hydrology may explain seasonal sliding dynamics, our model is unable to provide an explanation for surge-scale behavior, implicating a need for coupled hydrological and ice dynamics modeling of surge conditions. This work demonstrates the potential of using ice sheet models for alpine glaciology and provides a new nucleus for modeling of glacial hazards in alpine environments.