Abstract
Past fluctuations of the West Antarctic Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. However, the configuration and stability of the ice sheet during past interglacial periods remains uncertain. Here we present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. Fluctuations during glacial–interglacial cycles appear superimposed on a long-term trajectory of ice-surface lowering relative to the mountains. This implies that as a minimum, a regional ice sheet centred on the Ellsworth-Whitmore uplands may have survived Pleistocene warm periods. If so, it constrains the WAIS contribution to global sea level rise during interglacials to about 3.3 m above present.
Highlights
Past fluctuations of the West Antarctic Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level
The ice margin are two formerly glaciated zones marked by an upper erosional trimline (Fig. 1d), the latter recognized throughout the Ellsworth Mountains[27]
The simplest explanation of the pattern of cosmogenic nuclide data is that an ice margin fluctuated in elevation on the mountain flank (Fig. 4)
Summary
Past fluctuations of the West Antarctic Ice Sheet (WAIS) are of fundamental interest because of the possibility of WAIS collapse in the future and a consequent rise in global sea level. We present geomorphological evidence and multiple cosmogenic nuclide data from the southern Ellsworth Mountains to suggest that the divide of the WAIS has fluctuated only modestly in location and thickness for at least the last 1.4 million years. The winds cause ablation of surface ice that in turn causes a compensating upward flow of ice that brings basal debris to the ice-surface as blue-ice moraines[14,15] This ice-marginal, basally derived material is deposited higher on the mountain flanks and records past changes in ice thickness. Initial work in the Heritage Range revealed a scatter of ages of up to 400 ka in elevated blue-ice moraines[24,25] These data led to the untested hypothesis that the spread in ages represented the continuous presence of an ice sheet that fluctuated in thickness in response to glacial–interglacial cycles[14]. One can gain information on the age of deposition and possible subsequent overriding and disturbance by ice
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