Review article: Geothermal heat flow in Antarctica: current and future directions

Abstract

Abstract. Antarctic geothermal heat flow (GHF) affects the temperature of the ice sheet, determining its ability to slide and internally deform, as well as the behaviour of the continental crust. However, GHF remains poorly constrained, with few and sparse local, borehole-derived estimates and large discrepancies in the magnitude and distribution of existing continent-scale estimates from geophysical models. We review the methods to estimate GHF, discussing the strengths and limitations of each approach; compile borehole and probe-derived estimates from measured temperature profiles; and recommend the following future directions. (1) Obtain more borehole-derived estimates from the subglacial bedrock and englacial temperature profiles. (2) Estimate GHF from inverse glaciological modelling, constrained by evidence for basal melting and englacial temperatures (e.g. using microwave emissivity). (3) Revise geophysically derived GHF estimates using a combination of Curie depth, seismic, and thermal isostasy models. (4) Integrate in these geophysical approaches a more accurate model of the structure and distribution of heat production elements within the crust and considering heterogeneities in the underlying mantle. (5) Continue international interdisciplinary communication and data access.

Comment on “Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream” by Smith-Johnsen et al. (2020)

“…An indication of the fluid flux required to achieve 0.1 m yr −1 basal melting can be obtained by assuming that the melting is achieved by 100 • C aqueous fluids that melt basal ice at 0 • C while themselves cooling down to 0 • C. Using a heat capacity of 4.2 kJ kg −1 K −1 and a latent heat of 334 kJ kg −1 for melting ice, we obtain a required fluid flux of ∼ 2 × 10 −6 kg m −2 s −1 (or ∼ 0.07 m 3 m −2 yr −1 ). This is more than 3 orders of magnitude more than the 2-7 × 10 −10 kg m −2 s −1 expected for metamorphic fluid fluxes (Connolly and Thompson, 1989) that could potentially provide the hot fluids. Even the much lower estimated melting rate of 6.1 mm yr −1 of Buchardt and Dahl-Jensen (2007) would require >10 times more mass of hot fluid than expected.…”

Joint Inversion for Surface Accumulation Rate and Geothermal Heat Flow From Ice‐Penetrating Radar Observations at Dome A, East Antarctica. Part II: Ice Sheet State and Geophysical Analysis

“…As GHF models are utilized by researchers in different fields to those publishing the models, they cannot be independently evaluated by the user, and so accuracy in published uncertainty values is arguably more important than the accuracy of the model itself." While Burton-Johnson et al (2020) were referring to the Martos et al (2017) estimate with that quote, it applies even more strongly to the Shen et al (2020) estimate, which gives uncertainty values roughly half as large within our domain. The results of this sensitivity test show that those low uncertainty estimates, when used as a prior in our inversion, effectively prevented our model from fitting most of the observed water in our domain.…”

“…As GHF models are utilized by researchers in different fields to those publishing the models, they cannot be independently evaluated by the user, and so accuracy in published uncertainty values is arguably more important than the accuracy of the model itself.” While Burton‐Johnson et al. (2020) were referring to the Martos et al. (2017) estimate with that quote, it applies even more strongly to the Shen et al.…”

“…We feel that it is appropriate to quote Burton‐Johnson et al. (2020) at length on the topic of uncertainty estimates: “Without being critical of the model itself, it is reasonable to dispute the accuracy of the calculated uncertainties and suggest that although their calculation from the geophysical data may be logical, there may be a geological contribution to uncertainty (e.g., lithological variation in the lithosphere) that is not being considered. As GHF models are utilized by researchers in different fields to those publishing the models, they cannot be independently evaluated by the user, and so accuracy in published uncertainty values is arguably more important than the accuracy of the model itself.” While Burton‐Johnson et al.…”

Simulating the internal structure of the Antarctic Ice Sheet – towards a spatio-temporal calibration for ice-sheet modelling

“…3 C). Geothermal heat flux is uncertain for most parts of the Antarctic Ice Sheet and regional differences between published datasets can be substantial (Burton-Johnson et al, 2020;Talalay et al, 2020).…”