Ice surface lowering of Skelton Glacier, Transantarctic Mountains, since the Last Glacial Maximum: implications for retreat of grounded ice in the western Ross Sea

Abstract

Quantifying the contribution of the East Antarctic Ice Sheet (EAIS) to sea-level rise during the last deglaciation is complicated by the limited opportunities to constrain ice-sheet models. The nunatak, Escalade Peak, provides a gauge for past ice surface elevation changes and behaviour throughout the last glacial cycle. Geomorphological mapping, geological evidence and 10Be cosmogenic-nuclide exposure dating at Escalade Peak, provide new constraints on the ice surface history of the Skelton Névé since the Last Glacial Maximum (LGM). An elevation transect from the eastern margin of Escalade Peak indicates that the ice surface of the Skelton Névé was at least 50 m and perhaps >120 m higher than present during the LGM. In contrast, surface-exposure ages from a suite of inner moraines (blue-ice moraines) adjacent to Escalade Peak do not provide independent ice surface elevation constraints, but may provide an indirect constraint on the timing of thinning due to exhumation-ablation processes. Maximum simple exposure ages from the inner moraines suggest ice surface ablation was initiated by 19.2 ka, but the majority of ice surface lowering at Escalade Peak likely occurred after ∼15 ka and reached the present-day ice level at ∼6 ka. These findings suggest that slow flowing inland sites of EAIS outlet glaciers, such as southern Skelton Névé, experienced minimal ice surface elevation change since the LGM and record an EAIS outlet glacier and western Ross Sea retreat signature rather than widespread Ross Sea retreat. The ice surface lowering is likely to have been in response to retreat of the grounded ice in the western Ross Embayment causing a reduction in buttressing of the Skelton Glacier and draw down into the Ross Sea.