Due to a scale error in the 1970 map, the height of the glacier surface above sea-level was everywhere up to about 10% too large. It was possible to show, using these data, that the flow law “constants” derived, were only in fair agreement with previously published results ( Reference ThomasThomas1971). The accuracy of the flow-rate determinations depended primarily on the accuracy of the mapping and the reliability of point identification.
The points on this curve were obtained from the change in position of a set of marginal “teeth” which appear in successive aerial photographs taken between 19 ( Fig.2). In an earlier paper ( Reference HoldsworthHoldsworth 1974), longitudinal strain-rates were derived for Erebus Glacier Tongue (EGT) ( Fig.l) using the velocity gradient obtained from a plot of ice-flow rate versus distance along the tongue. Such oscillations may also lead to the calving of EGT although recent observations suggest that a hinge-line calving due to horizontal bending of EGT may be just as likely. Short-period, pseudo-elastic deformations occurring in EGT as a result of ocean wave-induced motion may be responsible for continually activating crevasses and producing the apparent “softening” effect in the creep of the thinner ice. Bending of EGT appears to be the result of current pressure exerted on the south side of the glacier, and computed bending strains seem to account for most of the observed curvature of EGT.īasal ice melting predominates over any possible refreezing melt rates along the south edge exceed basal melt rates by a factor of 5-10. The thinner ice appears to be “softer” than the thicker ice. Re-analysis of the stress and strain-rate data leads to flow law constants which are now more compatible with those of Thomas (1973).
The use of LANDSAT imagery and controlled aerial photography up to 1978 have enabled glacier flow rates and hence strain-rates to be determined more accurately than before. Recent measurements conducted on Erebus Glacier Tongue (EGT) have enabled improvements to be made to previous analyses of earlier data ( Holdsworth 1974).
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