Logan Elliott Mann, Colin R. Meyer, Alexander Robel, Elisa Mantelli

Understanding the formation and evolution of fast flowing ice streams is essential to projecting the centennial-scale response of ice sheets to climate forcings. Slow flowing glaciers or stagnant ice streams can slide at low velocities over a bed that is below the bulk melting point of ice, dissipating small amounts of frictional heat. This phenomenon is typically referred to as subtemperate sliding, and it complicates the assumed dichotomy between frozen and thawed beds embedded in many large-scale process-based ice sheet models. In this study, we allow for subtemperate sliding in a simple ice stream box model to investigate frictional heat dissipation at frozen ice-bed interfaces. We find that including subtemperate sliding leads to non-negligible frictional heat dissipation, which can accelerate sliding and lead to runaway acceleration of stagnant ice streams. These results suggest that subtemperate sliding and the associated thermo-frictional feedback occurs in longer timescales characterizing Heinrich events. On shorter, centennial timescales, subtemperate sliding is likely an important physical process to consider in modeling the potential reactivation of stagnant ice streams like Kamb Ice Stream.