Subglacial processes on an Antarctic ice stream bed. 2: Can modelled ice dynamics explain the morphology of mega-scale glacial lineations?

摘要

Mega-scale glacial lineations (MSGLs) are highly elongate subglacial bedforms associated with ice streaming. However, the link between MSGLs and rapid ice flow is largely qualitative, and there have been few attempts to quantitatively link their formation to ice flow characteristics (e.g. ice velocity, thickness, basal shear stress). We take measurements of MSGLs from a palaeo-ice stream that once occupied Marguerite Trough, Antarctic Peninsula and explore a range of possible correlations with ice dynamics generated from an ensemble of numerical modelling experiments that reproduce the deglaciation of the ice stream. Our results confirm that high mean ice velocities and a weak bed correlate with longer MSGLs. Furthermore, the height of MSGLs are low (2-3 m) where modelled basal shear stress is low, but their height tends to be higher and more variable where basal shear stress is larger. The mean density of MSGLs decreases as ice flux increases. Our analysis further suggests that the length of MSGLs is a function of basal ice velocity and time. Although our data/model correlations confirm the importance of ice velocity in MSGL formation, a significant challenge remains if we are to employ MSGLs as a quantifiable measure of past ice stream velocity.