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

Abstract

The lithospheric structure of Antarctica is still underexplored. Moho depth estimate studies are in disagreement by more than 10 km in several regions, including, for example, the hinterland of the Transantarctic Mountains. Taking account the sparseness of seismological stations and the nonuniqueness of potential field methods, inversions of Moho depth are performed here based on satellite gravity data in combination with currently available seismically constrained Moho depth estimates. Our results confirm that a lower density contrast at the Moho is present under East Antarctica than beneath West Antarctica. A comparison between the Moho depth derived from our inversion and an Airy‐isostatic Moho model also reveals a spatially variable buoyancy contribution from the lithospheric mantle beneath contrasting sectors of East Antarctica. Finally, to test the plausibility of different Moho depths scenarios for the Transantarctic Mountains‐Wilkes Subglacial Basin system, we present 2‐D lithospheric models along the Trans‐Antarctic Mountain Seismic Experiment/Gamburtsev Mountain Seismic experiment seismic profile. Our models show that if a moderately depleted lithospheric mantle of inferred Proterozoic age underlies the region, then a shallower Moho is more likely beneath the Wilkes Subglacial Basin. If however, refertilization processes occurred in the upper mantle, for example, in response to Ross‐age subduction, then a deeper Moho scenario is preferred. We conclude that 3‐D lithospheric modeling, coupled with the availability of new seismic information in the hinterland of the Transantarctic Mountains, is required to help resolve this controversy, thereby also reducing the ambiguities in geothermal heat flux estimation beneath this key part of the East Antarctic Ice Sheet.

Mapping Crustal Shear Wave Velocity Structure and Radial Anisotropy Beneath West Antarctica Using Seismic Ambient Noise

“…The higher phase velocities characterizing the WARS contrast starkly. As a proxy for crustal thickness, the amplitudes and geographic distribution of velocity anomalies at these periods is broadly consistent with results from receiver function (e.g., Chaput et al, 2014;Ramirez et al, 2016Ramirez et al, , 2017, surface wave (e.g., An et al, 2015;Shen et al, 2018), and gravity (e.g., Damiani et al, 2014;Jordan et al, 2010;O'Donnell & Nyblade, 2014;Pappa et al, 2019) studies.…”

“…Figure 11 suggests that the thickest crust (∼35-40 km) in the modeled region is found beneath the southern TAM and Haag Nunataks-Ellsworth Mountains, with slightly thinner crust occurring beneath MBL and the Antarctic Peninsula. However, the tomographic resolution degrades on the Peninsula (Figure 6), so our modeled crustal thickness there (∼32-35 km) is likely underestimated; satellite gravity data suggest that Geochemistry, Geophysics, Geosystems 10.1029/2019GC008459 the crust on the southern Peninsula is comparably thick to that beneath the Ellsworth Mountains (e.g., O'Donnell & Nyblade, 2014;Pappa et al, 2019).…”

Geothermal heat flow in Antarctica: current and future directions

“…Using the gravity-derived crustal thickness estimates, cross-sectional models of the mantle and lithospheric structure were calculated, with adjustments made to crustal density and crustal thickness until the models reflected the observed variation in gravity and elevation (Pappa et al, 2019b). By assigning assumed values of heat productivity and thermal conductivity values to the modelled cross-sections, surface heat flow was calculated along the line of the modelled cross-section ( Fig.…”

A Multivariate Approach for Mapping Lithospheric Domain Boundaries in East Antarctica

“…Ebbing et al () infer a number of domains in the East Antarctic interior from the curvature index of gravity field with topographic and isostatic correction and suggest the extent of cratonic lithosphere and orogens. Studies that includes both gravity and seismic data also find a heterogenous interior and provide strong arguments to suggest existence of domains (Baranov & Morelli, ; Baranov et al, ; Pappa et al, ). Our contribution complements these studies by providing a method for mapping the boundaries of such domains.…”