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Media type:
E-Article
Title:
Towards modelling of corrugation ridges at ice-sheet grounding lines
Contributor:
Hogan, Kelly A.;
Warburton, Katarzyna L. P.;
Graham, Alastair G. C.;
Neufeld, Jerome A.;
Hewitt, Duncan R.;
Dowdeswell, Julian A.;
Larter, Robert D.
Description:
<jats:p>Abstract. Improvements in the resolution of sea-floor mapping
techniques have revealed extremely regular, sub-metre-scale ridge landforms
produced by the tidal flexure of ice-shelf grounding lines as they retreated
very rapidly (i.e. at rates of several kilometres per year). Guided by such
novel sea-floor observations from Thwaites Glacier, West Antarctica, we
present three mathematical models for the formation of these corrugation
ridges at a tidally migrating grounding line (that is retreating at a
constant rate), where each ridge is formed by either constant till flux to
the grounding line, till extrusion from the grounding line, or the
resuspension and transport of grains from the grounding-zone bed. We find
that both till extrusion (squeezing out till like toothpaste as the ice
sheet re-settles on the sea floor) and resuspension and transport of
material can qualitatively reproduce regular, delicate ridges at a
retreating grounding line, as described by sea-floor observations. By
considering the known properties of subglacial sediments, we agree with
existing schematic models that the most likely mechanism for ridge formation
is till extrusion at each low-tide position, essentially preserving an
imprint of the ice-sheet grounding line as it retreated. However, when
realistic (shallow) bed slopes are used in the simulations, ridges start to
overprint one another, suggesting that, to preserve the regular ridges that
have been observed, grounding line retreat rates (driven by dynamic
thinning?) may be even higher than previously thought.
</jats:p>