Abstract
AbstractHypothesised 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 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. © 2018 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.
Highlights
Phillips et al (2017) propose that fracture patterns at Kvíárjökull (Figure 1), a temperate glacier in southeast Iceland, indicate that flow since c. 1940 has proceeded as a series of independently moving lobes or ‘pulses’ of ice (Figure 1(b)) originating in the upper glacier tongue
These authors have used ‘marked changes’ in crevasse patterns to divide the glacier surface into 27 domains, which are claimed to be individual pulses of ice separated by shear zones
We set out to test the pulsed axial flow hypothesis of Phillips et al (2017) because crevasse patterns are more commonly interpreted to reflect local tensile stresses caused by undulations at the glacier bed
Summary
Phillips et al (2017) propose that fracture (i.e. crevasse) patterns at Kvíárjökull (Figure 1), a temperate glacier in southeast Iceland, indicate that flow since c. 1940 has proceeded as a series of independently moving lobes or ‘pulses’ of ice (Figure 1(b)) originating in the upper glacier tongue. 1940 has proceeded as a series of independently moving lobes or ‘pulses’ of ice (Figure 1(b)) originating in the upper glacier tongue. The work presented by Philips et al (2017) sets a new standard for glacier fracture mapping It is essential for the development of glaciological theory that, as in all fields of science, new methods are trialled that seek to challenge received wisdom. Swift et al (2006) have previously documented the presence of a glacier-wide, transverse, ogive-origin foliation at Kvíárjökull This foliation is largely overlooked by Phillips et al (2017), yet could provide strong supporting evidence for their theory if it can be shown that independently migrating lobes of ice have caused the foliation to be sufficiently offset
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