Going against the flow: testing the hypothesis of pulsed axial glacier flow

Hypothesised lobe-like flow of a temperate glacier in southeast Iceland, proposed from an analysis of ice surface crevassing patterns, is appraised from both empirical and theoretical perspectives. The hypothesis comprises the migration of individual lobes (or ‘pulses’) of ice through the glacier body, with central lobes migrating more rapidly along a narrow, central, ‘axial flow corridor’. Our alternative hypothesis is that crevasse patterns at this glacier instead reflect simple surface ice responses to stresses caused by flow over uneven bed topography. To substantiate our rejection of the lobe-like, pulsed axial flow hypothesis, we provide: (a) evidence for a prominent transverse foliation that exhibits no evidence of shear of the required magnitude to support the hypothesis; and (b) an analysis of ice surface displacement, obtained by feature tracking, that shows a uniform flow field throughout the glacier tongue. We argue that caution needs to be exercised when interpreting glacier flow solely from crevasse patterns and observations of minor displacements along near-surface fractures and other features.