C024-09
Holocene Ice-Elevation and Extent Changes at Roberts Massif, Central Transantarctic Mountains

Wednesday, 9 December 2020: 05:55
Virtual
Margaret S Jackson1, Gordon R Bromley1,2, Greg Balco3, Alexandra Balter-Kennedy4,5 and Holly Thomas2, (1)National University of Ireland Galway, Geography, Galway, Ireland, (2)University of Maine, Earth and Climate Sciences and Climate Change Institute, Orono, ME, United States, (3)Berkeley Geochronology Center, Berkeley, CA, United States, (4)Lamont -Doherty Earth Observatory, Earth and Climate Sciences, Palisades, ME, United States, (5)University of Maine, Earth and Climate Sciences, Orono, ME, United States
Abstract:
We report new cosmogenic surface-exposure ages from Roberts Massif in the central Transantarctic Mountains that constrain changes in East Antarctic Ice Sheet (EAIS) mass balance during the Holocene Epoch. We then compare these data with new and previously reported surface-exposure ages from Roberts Massif that span the Quaternary and Pliocene periods in order to contextualise the Holocene chronology and to evaluate the potential drivers of EAIS mass balance over time.

Establishing the timing and magnitude of past changes to EAIS mass balance is a crucial prerequisite for assessing the sensitivity of the ice sheet to changing climate conditions. Mapping and dating past EAIS extents provides direct constraint on the temporal and spatial variability of past ice-sheet-margin change. Roberts Massif is abutted by the EAIS and features numerous glacial deposits that attest to past ice-sheet extent and are amenable for cosmogenic surface-exposure dating. Prior work to map and date past EAIS fluctuations at Roberts Massif yields information on local ice-sheet changes during and since the Miocene (~15 Ma), and provides useful context for investigating more recent EAIS change.

Here we present new cosmogenic surface-exposure ages from Roberts Massif that bear directly on local EAIS elevation changes during the Holocene. We also present a chronology of ice-extent change of a land-terminating tongue of the EAIS at Roberts Massif. Preliminary results suggest that EAIS elevation lowered during the Holocene. However, ice-tongue extent may have fluctuated out of phase with EAIS elevation changes prior to, and perhaps during, the Holocene Epoch. These results indicate that ice tongues such as the one documented here may respond to different forcing mechanisms than does the local EAIS (as reflected by elevation change). Alternatively, these same forcing mechanisms may affect these ice masses on different timescales. Together with previously reported records of EAIS fluctuations over the last ~5 Ma, these data yield information on the timing and magnitude of past EAIS mass balance changes at Roberts Massif and the potential mechanisms that control these glaciers over millennial and orbital timescales, including during the Holocene.

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