Hot rocks in a cold place: high sub-glacial heat flow in East Antarctica

Abstract

Numerical models are the primary predictive tools for understanding the dynamic behavior of the Antarctic ice sheet. But a key boundary parameter -sub-glacial heat flow -remains poorly constrained. We show that variations in abundance and distribution of heat-producing elements within the Antarctic continental crust result in greater and more variable regional sub-glacial heat flows than currently assumed in ice modeling studies. Such elevated heat flows would fundamentally impact on ice sheet behaviour and highlight that geological controls on heat flow must be considered to obtain more accurate and refined predictions of ice mass balance and sea level change.

Crustal heat production and estimate of terrestrial heat flow in central East Antarctica, with implications for thermal input to the East Antarctic ice sheet

“…As a group they are distinctly different from the regional pattern shown by anomalously warm Proterozoic crust in central Australia with average q o = 80 mW m −2 (McLaren et al, 2003), which has been suggested to extend across the Wilkes Land margin of Antarctica based on Gondwana supercontinent reconstructions (Carson et al, 2014;Aitken et al, 2014). Despite general age similarities among some of the clast population with parts of the Gawler Craton, and basement age correlations that indicate continuity of Mawson-type crust into the Wilkes sector of East Antarctica (Goodge and Fanning, 2016), the proxy heat production determinations and heat flow estimates provided here suggest that central portions of the East Antarctic ice sheet are underlain by stable continental crust with quite normal thermal properties represented by average values of heat production of about 2.5 µW m −3 and heat flow of about 50 mW m −2 .…”

“…from Archean and Paleoproterozoic bedrock exposed in the coastal region of southern Prydz Bay (2.4-2.6 µW m −3 ; Carson and Pittard, 2012; Carson et al, 2014). Four of the clasts give high values between 4.0 and 7.5 µW m −3 , which are similar to global occurrences of crust characterized by high heat production (Mareschal and Jaupart, 2013;Jaupart et al, 2016) and exemplified by the Central Australian Heat Flow Province (Neumann et al, 2000;Sandiford and McLaren, 2002;McLaren et al, 2003).…”

“…Compared to examples globally (Mareschal and Jaupart, 2013;Jaupart et al, 2016;Artemieva et al, 2017), the Proterozoic igneous rocks in this study indicate that heat production in central East Antarctica is like that of typical www.the-cryosphere.net/12/491/2018/ The Cryosphere, 12, 491-504, 2018 continental shield areas and demonstrably different from the anomalously warm region represented by the CAHFP. Geological and geophysical correlations between cratonic rocks in southern Australia (Gawler craton) and the Wilkes Land region of East Antarctica (e.g., Oliver and Fanning, 1997;Aitken et al, 2014;Goodge and Finn, 2010;Boger, 2011;Fanning, 2010, 2016), have been used as the basis for extrapolating high heat flow values reported for the CAHFP into East Antarctica (Carson et al, 2014). To date, no direct constraint on terrestrial heat flow has been provided for this area of Wilkes Land, and how far south toward Dome C and the upper Aurora and Wilkes subglacial basins this province may extend is not clear.…”

“…Using a measured temperature profile in the EPICA ice borehole at Dome C, Fischer et al (2013) derived a geothermal heat flux of about 54 mW m −2 by fitting a model of heat flow and basal ice melting to the thermal profile. A geological approach was taken by Carson et al (2014), who derived heat flow using values for heat production estimated from the abundances of radioactive elements in crustal rocks sampled from outcrop near the Amery Ice Shelf (compiled by Carson and Pittard, 2012). From a coastal transect across rock exposures at Prydz Bay, the resulting profile indicates that heat flow in this area of Archean to Proterozoic igneous and metamorphic crust is highly variable over a distance of about 200 km, ranging from an average of 31 mW m −2 in the Vestfold Hills to 44 mW m −2 in the Rauer Islands and 55-70 mW m −2 in the area of southern Prydz Bay.…”

“…Their model results thus show variable heat flow governed to first order by the age and type of crust represented and punctuated by heat production spikes contributed from Th-rich granitoids. Although much of the area underlying the Rauer Islands and Vestfold Hills has low heat flow (< 50 mW m −2 ) typical of Proterozoic and Archean crust, Carson et al (2014) emphasized that some early Paleozoic granites with anomalously high heat production can cause local elevation of heat flow (> 80 mW m −2 ), as observed in the Central Australian Heat Flow Province (CAHFP; McLaren et al, 2003). Thus, spatially coarse models of heat flow based on geophysical data across East Antarctica indicate relatively typical continental values ranging from about 35 to 60 mW m −2 , yet there are (Fretwell et al, 2013).…”