In an ice sheet, an unconformity is the surface between two packets of ice with discontinuous ages.Unconformities can form by ice flow through a surface zone where snow is scoured.Unconformities present both a challenge to the preservation of continuous climate records and an opportunity to assess the stability of surface conditions and ice flow on glacial-interglacial timescales.In previous work, scour zones have been shown to be persistent on timescales of hundreds to thousands of years by mapping the resulting unconformity traces in shallow radar data sets.Here we use airborne ice-penetrating radar collected along approximate ice-flow lines on the southern flank of Dome A to trace unconformities through the full stratigraphic ice column.These unconformities extend hundreds of kilometers horizontally and cross-cut ice of approximately ~200 ka age.Kinematic ice-flow modeling shows the simplest explanation for the trace of the unconformities is persistent surface scour and stable ice-flow conditions for the past two glacial-interglacial cycles.These results indicate stability of East Antarctic ice flow through glacial-interglacial cycles and allow the location of stratigraphic disturbances to be avoided by careful selection of future ice-coring sites, even on the flanks of ice-sheet domes.
Fudge et al. (Thu,) studied this question.