Helheim velocity controlled both by terminus effects and subglacial
hydrology with distinct realms of influence
Abstract
Two outstanding questions for future Greenland predictions are (1) how
enhanced meltwater draining beneath the ice sheet will impact the
behavior of large tidewater glaciers, and (2) to what extent tidewater
glacier velocity is driven by changes at the terminus versus changes in
sliding velocity due to meltwater input. We present a two-way coupled
framework to simulate the nonlinear feedbacks of evolving subglacial
hydrology and ice dynamics using the Subglacial Hydrology And Kinetic,
Transient Interactions (SHAKTI) model within the Ice-sheet and Sea-level
System Model (ISSM). Through coupled simulations of Helheim Glacier, we
find that terminus effects dominate the seasonal velocity pattern up to
15 km from the terminus, while hydrology primarily drives the velocity
response upstream. With increased melt, the hydrology influence yields
seasonal acceleration of several hundred meters per year in the
interior, suggesting that hydrologic forcing will play an important role
in future mass balance of tidewater glaciers.