The crustal thickness of West Antarctica

Abstract

P‐to‐S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica and the Transantarctic Mountains deployment of seismographic stations provide new estimates of crustal thickness across West Antarctica, including the West Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, and the Transantarctic Mountains (TAM) margin. We show that complications arising from ice sheet multiples can be effectively managed and further information concerning low‐velocity subglacial sediment thickness may be determined, via top‐down utilization of synthetic receiver function models. We combine shallow structure constraints with the response of deeper layers using a regularized Markov chain Monte Carlo methodology to constrain bulk crustal properties. Crustal thickness estimates range from 17.0±4 km at Fishtail Point in the western WARS to 45±5 km at Lonewolf Nunataks in the TAM. Symmetric regions of crustal thinning observed in a transect deployment across the West Antarctic Ice Sheet correlate with deep subice basins, consistent with pure shear crustal necking under past localized extension. Subglacial sediment deposit thicknesses generally correlate with trough/dome expectations, with the thickest inferred subice low‐velocity sediment estimated as ∼0.4 km within the Bentley Subglacial Trench. Inverted PRFs from this study and other published crustal estimates are combined with ambient noise surface wave constraints to generate a crustal thickness map for West Antarctica south of 75°S. Observations are consistent with isostatic crustal compensation across the central WARS but indicate significant mantle compensation across the TAM, Ellsworth Block, MBL dome, and eastern and western sectors of thinnest WARS crust, consistent with low density and likely dynamic, low‐viscosity high‐temperature mantle.

Large ensemble modeling of the last deglacial retreat of the West Antarctic Ice Sheet: comparison of simple and advanced statistical techniques

“…The best-fit range for the asthenospheric relaxation timescale TAUAST values is quite broad, including the prior reference value ∼ 3 kyr but extending to shorter times ∼ 1 kyr. This may be connected with low upper-mantle viscosities and thin crustal thicknesses suggested in recent work (Whitehouse et al, 2012b;Chaput et al, 2014), which will be examined in further work with full Earth models (Gomez et al, 2013(Gomez et al, , 2015Konrad et al, 2015).…”

“…As in many large-scale ice-sheet models, our bedrock response is represented by a simple Earth model consisting of an elastic plate over a local e-folding relaxation towards isostatic equilibrium (elastic lithosphere relaxing asthenosphere). Based on more sophisticated global Earth models, the asthenospheric e-folding timescale is commonly set to 3 kyr (e.g., Gomez et al, 2013), but note that recent geophysical studies suggest considerably shorter timescales for some West Antarctic regions (Whitehouse et al, 2012b;Chaput et al, 2014). In further work we plan to perform large ensembles with the icesheet model coupled to a full Earth model, extending Gomez et al (2013Gomez et al ( , 2015.…”

Antarctic ice sheet thickness estimation using the horizontal-to-vertical spectral ratio method with single-station seismic ambient noise

“…Over the past two decades, several temporary seismic arrays have been deployed in Antarctica, including the TransAntarctic Mountains Seismic Experiment (TAMSEIS, 2000(TAMSEIS, -2003 (Lawrence et al, 2006), the Gamburtsev Antarctic Mountains Seismic Experiment (GAMSEIS, 2007(GAMSEIS, -2012 (Hansen et al, 2010) and the Polar Earth Observing Network/Antarctic Network (POLENET/ANET, 2007-2016) (Chaput et al, 2014). Despite their relatively sparse distribution compared to many dense seismic arrays on other continents, these three arrays combined effectively cover East and West Antarctica as well as the Transantarctic Mountains region (Fig.…”

Low post-glacial rebound rates in the Weddell Sea due to Late Holocene ice-sheet readvance

“…The thickness of the lithosphere and the viscosity of the upper and lower mantle are user-defined parameters. It has been suggested that there is considerable lateral variability beneath the Antarctic continent (Morelli and Danesi, 2004;Chaput et al, 2014), from the relatively thin lithosphere and low viscosity mantle believed appropriate for the West Antarctic rift system to the thicker lithosphere and higher viscosity mantle of the craton below East Antarctica. Consequently, there have been considerable differences in the Earth model used in previous Antarctic GIA modelling studies (Peltier, 2004;Whitehouse et al, 2012b;Ivins et al, 2013).…”