Abstract
AbstractThe East Antarctic Ice Sheet (EAIS) is underlain by a series of low‐lying subglacial sedimentary basins. The extent, geology, and basal topography of these sedimentary basins are important boundary conditions governing the dynamics of the overlying ice sheet. This is particularly pertinent for basins close to the grounding line wherein the EAIS is grounded below sea level and therefore potentially vulnerable to rapid retreat. Here we analyze newly acquired airborne geophysical data over the Pensacola‐Pole Basin (PPB), a previously unexplored sector of the EAIS. Using a combination of gravity and magnetic and ice‐penetrating radar data, we present the first detailed subglacial sedimentary basin model for the PPB. Radar data reveal that the PPB is defined by a topographic depression situated ~500 m below sea level. Gravity and magnetic depth‐to‐source modeling indicate that the southern part of the basin is underlain by a sedimentary succession 2–3 km thick. This is interpreted as an equivalent of the Beacon Supergroup and associated Ferrar dolerites that are exposed along the margin of East Antarctica. However, we find that similar rocks appear to be largely absent from the northern part of the basin, close to the present‐day grounding line. In addition, the eastern margin of the basin is characterized by a major geological boundary and a system of overdeepened subglacial troughs. We suggest that these characteristics of the basin may reflect the behavior of past ice sheets and/or exert an influence on the present‐day dynamics of the overlying EAIS.
Highlights
Low‐lying subglacial topography across West Antarctica and around large tracts of the margin of East Antarctica is hypothesized to render the overlying sectors of the Antarctic Ice Sheet vulnerable to rapid retreat or even catastrophic collapse in a warming world (Mercer, 1978; Schoof, 2003; Thomas, 1979)
Recent numerical ice sheet simulations indicate that the majority of East Antarctic Ice Sheet (EAIS) retreat in the near‐future will be focused within the Wilkes, Recovery and Aurora Subglacial Basins (DeConto & Pollard, 2016; Golledge et al, 2017, 2015; Mengel & Levermann, 2014; Pollard et al, 2015), from which ice mass loss will potentially contribute 9–15 m of sea level rise in a warming world (Gasson et al, 2015)
The valley floors are observed at depths of at least 1.5 km below sea level, they are often not imaged by radio‐echo sounding (RES) (Figure 6)
Summary
Low‐lying subglacial topography across West Antarctica and around large tracts of the margin of East Antarctica is hypothesized to render the overlying sectors of the Antarctic Ice Sheet vulnerable to rapid retreat or even catastrophic collapse in a warming world (Mercer, 1978; Schoof, 2003; Thomas, 1979). Recent numerical ice sheet simulations indicate that the majority of East Antarctic Ice Sheet (EAIS) retreat in the near‐future will be focused within the Wilkes, Recovery and Aurora Subglacial Basins (DeConto & Pollard, 2016; Golledge et al, 2017, 2015; Mengel & Levermann, 2014; Pollard et al, 2015), from which ice mass loss will potentially contribute 9–15 m of sea level rise in a warming world (Gasson et al, 2015) Exploration of these basins using airborne geophysics has brought about increased understanding of their extent, subglacial topography, geology, and tectonic architecture (Aitken et al, 2016; Diez et al, 2018; Ferraccioli et al, 2009; Frederick et al, 2016; Maritati et al, 2016; Paxman et al, 2017; Ross et al, 2012). Characterization of subglacial basins has the potential to improve future ice sheet projections and can inform models of EAIS dynamics in past warmer climates (Aitken et al, 2016; Paxman et al, 2018; Young et al, 2011), which may represent an analog for a future warmer world
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