C052-03
Basal Ice Stratigraphy from Mercer Ice Stream, West Antarctica: Implications for sub ice stream accretionary processes

Monday, 14 December 2020: 17:36
Virtual
Timothy Campbell1, Mark L Skidmore1, Matthew Siegfried2, John Winans3, Bob Zook4, John C Priscu5 and SALSA Science Team, (1)Montana State University, Earth Sciences, Bozeman, MT, United States, (2)Colorado School of Mines, Department of Geophysics, Golden, CO, United States, (3)Northern Illinois University, Department of Computer Science, DeKalb, United States, (4)University of Nebraska Lincoln, Antarctic Science Management Office, Lincoln, NE, United States, (5)Montana State University, Land Resources and Environmental Science, Bozeman, MT, United States
Abstract:
The basal conditions of the Siple Coast ice streams remain poorly understood due to limited direct observations and measurements. In the 2018-2019 austral summer, we used a hot-water drill to access Mercer Subglacial Lake located on Mercer Ice Stream, West Antarctica. We observed a ~6 m thick basal ice sequence directly above the ice-water interface of Mercer Subglacial Lake, from which we can develop new constraints on ice stream subglacial conditions and processes. Based on image analysis of the borehole walls, the basal ice sequence was composed of two main facies that were differentiated by debris content. The basal massive facies contained up to 20 times more sediment than the basal dispersed facies. Variations in basal ice stratigraphy reflect changes in accretionary basal conditions. We describe potential basal ice formation processes using models developed for Kamb Ice Stream, a nearby Siple Coast ice stream and discuss the implications for upstream basal conditions beneath the Mercer Ice Stream.
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