Understanding the evolution of the ice-bed interface is fundamentally important for gaining insight into the dynamics of ice masses and how subglacial landforms are created. However, the formation of the suite of landforms generated at this boundary - subglacial bedforms - is a contentious issue that is yet to be fully resolved. Bedforms formed in aeolian, fluvial, and marine environments either belong to separate morphological populations or are thought to represent a continuum of forms generated by the same governing processes. For subglacial bedforms, a size and shape continuum has been hypothesised, yet it has not been fully tested. Here we analyse the largest data set of subglacial bedform size and shape measurements ever collated (96,900 bedforms). Our results show that flutes form a distinct population of narrow bedforms. However, no clear distinction was found between drumlins and megascale glacial lineations (MSGLs), which form a continuum of subglacial lineations. A continuum of subglacial ribs also exists, with no clear size or shape distinctions indicating separate populations. Furthermore, an underreported class of bedform with no clear orientation to ice flow (quasi-circular bedforms) overlaps with the ribbed and lineation continua and typically occurs in spatial transition zones between the two, potentially merging these three bedform types into a larger continuum.
Bibliographical noteThe authors thank R.D. Larter, M. Ross, 2 anonymous reviewers, and the editor for their useful comments which improved this manuscript. J.C.E. thanks Kathy and Chris Denison for funding his PhD. This work was initiated and supported by a NERC grant (NE/D011175/1) to C.D.C. M.S. was supported by a NERC new investigator grant (NE/J004766/1) and C.R.S., a Philip Leverhulme Prize. S.L.G. acknowledges the University of Sheffield, the Swedish Research Council, and Linnaeus grants to Johan Kleman and the Bolin Centre for Climate Research. A.L.C.H acknowledges BGS NERC PhD studentship (NE/S/A/2004/12102). We thank Andrew Fowler and Richard Hindmarsh for fruitful discussions.
- Ribbed moraine
- Subglacial bedforms