Modeling Satellite Gravity Gradient Data to Derive Density, Temperature, and Viscosity Structure of the Antarctic Lithosphere

Abstract

In this study we combine seismological and petrological models with satellite gravity gradient data to obtain the thermal and compositional structure of the Antarctic lithosphere. Our results indicate that Antarctica is largely in isostatic equilibrium, although notable anomalies exist. A new Antarctic Moho depth map is derived that fits the satellite gravity gradient anomaly field and is in good agreement with independent seismic estimates. It exhibits detailed crustal thickness variations also in areas of East Antarctica that are poorly explored due to sparse seismic station coverage. The thickness of the lithosphere in our model is in general agreement with seismological estimates, confirming the marked contrast between West Antarctica (<100 km) and East Antarctica (up to 260 km). Finally, we assess the implications of the temperature distribution in our model for mantle viscosities and glacial isostatic adjustment. The upper mantle temperatures we model are lower than obtained from previous seismic velocity studies. This results in higher estimated viscosities underneath West Antarctica. When combined with present‐day uplift rates from GPS, a bulk dry upper mantle rheology appears permissible.

Geothermal heat flow in Antarctica: current and future directions

“…6). A 3D lithospheric model has since been published (Pappa et al, 2019a), and a map of Antarctica's resultant estimated GHF is in preparation for publication (pers. comms.…”

“…Steady-state thermal modelling is thus more applicable to the old, stable crust of East Antarctica; particularly if the heat flow and isostasy of the conjugate margins are considered (Hasterok and Gard, 2016;Pollett et al, 2019). However, differences between the crustal thickness based on gravity modelling and isostatic elevation modelling may indicate variable densities and/or compositions of the underlying mantle (Pappa et al, 2019b(Pappa et al, , 2019a).…”

“…geophysically-derived models (Leat et al, 2018;Pappa et al, 2019bPappa et al, , 2019a. Beneath the Antarctic ice sheet,…”

“…The assumption of a homogenous mantle composition beneath East Antarctica is challenged by discrepancies between the Moho depth models derived by gravity and isostatic modelling (Pappa et al, 2019b(Pappa et al, , 2019a, as this indicates variable lithospheric mantle densities, or deeper mantle effects on topography. A review of the available mantle xenoliths and mantle-derived basalt chemistry may be able to constrain the composition of the mantle beneath Antarctica, and thermal-isostatic modelling may be able to identify these regions of anomalous mantle anomalies (as in the Australian study of Hasterok and Gard, 2016).…”

Pangea Rifting Shaped the East Antarctic Landscape

“…The most significant morphological variations across East Antarctica broadly correlate with the Precambrian domains of Australo‐Antarctica and Indo‐Antarctica, which amalgamated during the ~600–550 Ma assembly of Gondwana (e.g., Mulder et al, 2019). Despite preserving Precambrian crust with broadly similar thicknesses (Pappa et al, 2019), these two domains exhibit remarkably distinct hypsometry (O'Donnell & Nyblade, 2014; Figure 1a). Indo‐Antarctica possesses elevated, high‐relief topography above the global average with narrow and deep rift basins (Ferraccioli et al, 2011).…”