Bedrock Erosion Surfaces Record Former East Antarctic Ice Sheet Extent

Abstract

East Antarctica hosts large subglacial basins into which the East Antarctic Ice Sheet (EAIS) likely retreated during past warmer climates. However, the extent of retreat remains poorly constrained, making quantifying past and predicted future contributions to global sea level rise from these marine basins challenging. Geomorphological analysis and flexural modeling within the Wilkes Subglacial Basin are used to reconstruct the ice margin during warm intervals of the Oligocene-Miocene. Flat-lying bedrock plateaus are indicative of an ice sheet margin positioned >400-500 km inland of the modern grounding zone for extended periods of the Oligocene-Miocene, equivalent to a 2-m rise in global sea level. Our findings imply that if major EAIS retreat occurs in the future, isostatic rebound will enable the plateau surfaces to act as seeding points for extensive ice rises, thus limiting extensive ice margin retreat of the scale seen during the early EAIS. Plain Language SummaryThe Wilkes Subglacial Basin is a large, low-lying topographic depression situated beneath the Antarctic Ice Sheet. Because the land surface of the basin is currently situated below sea level, it is a potential site of ice sheet collapse and rapid retreat in a warming world. Understanding this landscape and how it has evolved through time in relation to past climate and sea level is therefore key to understanding the future dynamics of this part of the ice sheet. Here we report the discovery, using ice-penetrating radar data sets, of extensive subglacial bedrock plateaus within the Wilkes Subglacial Basin. We analyze the geomorphology of these plateau surfaces and reconstruct the evolution of the subglacial landscape through time. Our results indicate that this part of the Wilkes Subglacial Basin was free of ice for extensive and prolonged periods of time during the early stages of ice sheet development. These constraints on past ice sheet extent, together with our landscape reconstruction, can be used by the ice sheet modeling community to better understand the likely future dynamics of this part of the Antarctic Ice Sheet.

Moho Depths of Antarctica: Comparison of Seismic, Gravity, and Isostatic Results

“…A similar setting may be envisaged in particular for the back‐arc regions of the Ross Orogen that may in parts underlie the Wilkes Subglacial Basin (e.g., Ferraccioli, Armadillo, Jordan, et al, ; Jordan et al, ). However, there are complicating effects in EANT, due to the much more recent Cenozoic uplift of the TAM (at the former site of the Ross Orogen) and the associated lithospheric flexure of the craton and its margin beneath the Wilkes Subglacial Basin (e.g., Paxman et al, , , and references therein). Irrespectively, however, we also note that some potentially conjugate Precambrian terranes in Australia that lie along the eastern edge of the Gawler Craton appear to have anomalously thick crust, most notably the seismically defined Numil terrane that has crust up to 45 km thick close to a proposed major suture zone of inferred Paleoproterozoic or even older Archaean age (Betts et al, ; Curtis & Thiel, ).…”

“…Moho depth estimates from seismological studies differ for the same station by up to 10 km, even along a relatively well‐studied profile (Figure ). The profile stretches from the TAM to the GSM (Creyts et al, ; Paxman et al, ) crossing the southern Wilkes Subglacial Basin (Ferraccioli et al, ; Ferraccioli, Armadillo, Jordan, et al, ; Ferraccioli & Bozzo, ; Jordan et al, ; Paxman et al, , ; Studinger et al, ). Seismic data have been acquired by deployments from the TAMSEIS (Hansen et al, ; Lawrence et al, , ) and the GAMSEIS (Kanao et al, ) experiments.…”

The Role of Lithospheric Flexure in the Landscape Evolution of the Wilkes Subglacial Basin and Transantarctic Mountains, East Antarctica

“…The black lines denote outlines of sub‐basins within the WSB (Ferraccioli, Armadillo, Jordan, et al, ). The yellow dashed lines mark the outline of flat bedrock plateaus (Paxman et al, ). Abbreviations: AST, Adventure Subglacial Trench; AsST, Astrolabe Subglacial Trench; BSH, Belgica Subglacial Highlands; CB, Central Basin; CT, Concordia Trench; EB, Eastern Basin; MSZ, Mertz Shear Zone; PAF, Prince Albert Fault; RG, Rennick Graben; RSH, Resolution Subglacial Highlands; WB, Western Basin.…”

Subglacial Geology and Geomorphology of the Pensacola‐Pole Basin, East Antarctica

“…The large-scale geomorphology of Antarctica's subglacial topography is an important repository of information relating to geology and past processes of landscape evolution Jamieson et al, 2014;Paxman et al, 2018;Young et al, 2011). Antarctic ice thickness and bedrock elevation are determined using (predominantly airborne) RES surveys.…”

“…These parameters lead to improved understanding of the tectonic and surface processes responsible for shaping the modern-day topography of subglacial East Antarctica, and in turn the dynamics of the overlying EAIS. Hence, characterization of subglacial basins has the potential to improve future ice sheet projections and can also inform models of EAIS dynamics in past warmer climates Paxman et al, 2018;Young et al, 2011), which may represent an analog for a future warmer world.…”