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Geothermal heat flow is an important boundary condition for ice sheets, affecting, for example, basal melt rates, but for ice-covered regions, we only have sparse heat flow observations with partly high uncertainty of up to 30 m W m -2. In this study, we first investigate the agreement between such pointwise heat flow observations and solid Earth models, applying a 1D steady-state approach to perform a statistical analysis for the entire Arctic region. We find that most of the continental heat flow observations have a high reliability and agreement to solid Earth models, except a few data points, such as, for example, the NGRIP (North Greenland Ice Core Project) point in central Greenland. For further testing, we perform a conditional simulation with focus on Greenland in which the local characteristics of heat flow structures can be considered. Simple kriging shows that including or excluding the less reliable NGRIP point has a large influence on the surrounding heat flow. The geostatistical analysis with the conditional simulation supports the assumption that NGRIP might not only be problematic for representing a regional feature but likely is an outlier. Basal melt estimates show that such a local spot of high heat flow results in local high basal melt rates but leads to less variation than existing geophysical models. [ABSTRACT FROM AUTHOR]

There is currently poor scientific agreement on whether the ice–bed interface is frozen or thawed beneath approximately one third of the Greenland ice sheet. This disagreement in basal thermal state results, at least partly, from differences in the subglacial geothermal heat-flow basal boundary condition used in different ice-flow models. Here, we employ seven widely used Greenland geothermal heat-flow maps in 10 000-year spin-ups of the Community Ice Sheet Model (CISM). We perform two spin-ups: one nudged toward thickness observations and the other unconstrained. Across the seven heat-flow maps, and regardless of unconstrained or nudged spin-up, the spread in basal ice temperatures exceeds 10 ∘ C over large areas of the ice–bed interface. For a given heat-flow map, the thawed-bed ice-sheet area is consistently larger under unconstrained spin-ups than nudged spin-ups. Under the unconstrained spin-up, thawed-bed area ranges from 33.5 % to 60.0 % across the seven heat-flow maps. Perhaps counterintuitively, the highest iceberg calving fluxes are associated with the lowest heat flows (and vice versa) for both unconstrained and nudged spin-ups. These results highlight the direct, and non-trivial, influence of the heat-flow boundary condition on the simulated equilibrium thermal state of the ice sheet. We suggest that future ice-flow model intercomparisons should employ a range of basal heat-flow maps, and limit direct intercomparisons with simulations using a common heat-flow map. [ABSTRACT FROM AUTHOR]

Geothermal heat flow is an important boundary condition for ice sheet, affecting for example basal melt rates, but for ice covered regions we only have sparse heat flow observations with partly high uncertainty. In this study, we first investigate the agreement between such point-wise heat flow observations and Solid Earth models, applying a 1D steady state approach to perform a statistical analysis for the entire Arctic region. We find that most of the continental heat flow observations have a high reliability and agreement to Solid Earth models, except a few data points, as for example the NGRIP point in Central Greenland. For further testing, we perform a conditional simulation with focus on Greenland, in which the local characteristics of heat flow structures can be considered. Simple kriging shows that including or excluding the less reliable NGRIP point has a large influence on the surrounding heat flow. The geostatistical analysis with the conditional simulation supports the assumption that NGRIP might not only be problematic for representing a regional feature but likely is an outlier. Basal melt estimates show that such a local spot of high heat flow results in local high basal melt rates, but leads to less variation than existing geophysical models. [ABSTRACT FROM AUTHOR]

There is currently poor scientific agreement whether the ice-bed interface is frozen or thawed beneath approximately one-third of the Greenland ice sheet. This disagreement in basal thermal state results, at least partly, from a diversity of opinion in the subglacial geothermal heat flow basal boundary condition employed in different ice-flow models. Here, we employ seven Greenland geothermal heat flow maps in widespread use to 10,000-year spin ups of the Community Ice Sheet Model (CISM). We perform both a fully unconstrained transient spin up, as well as a nudged spin up that conforms to Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) protocol. Across the seven heat flow maps, and regardless of unconstrained or nudged spin up, the spread in basal ice temperatures exceeds 10 °C over large areas of the ice-bed interface. For a given heat flow map, thawed-bedded ice-sheet area is consistently larger under unconstrained spin ups than nudged spin ups. Under the unconstrained spin up, thawed-bedded area ranges from 33.5 to 60.0 % across the seven heat flow maps. Perhaps counterintuitively, the highest iceberg calving fluxes are associated with the lowest heat flows (and vice versa) for both unconstrained and nudged spin ups. This highlights the direct, and non-trivial, influence of choice of heat flow boundary condition on the simulated equilibrium thermal state of the ice sheet. We suggest that future ice-flow model intercomparisons should employ a range of basal heat flow maps, and limit direct intercomparisons to simulations employing a common heat flow map. [ABSTRACT FROM AUTHOR]

We compile, analyse and map all available geothermal heat flow measurements collected in and around Greenland into a new database of 419 sites and generate an accompanying spatial map. This database includes 290 sites previously reported by the International Heat Flow Commission (IHFC), for which we now standardize measurement and metadata quality. This database also includes 129 new sites, which have not been previously reported by the IHFC. These new sites consist of 88 offshore measurements and 41 onshore measurements, of which 24 are subglacial. We employ machine learning to synthesize these in situ measurements into a gridded geothermal heat flow model that is consistent across both continental and marine areas in and around Greenland. This model has a native horizontal resolution of 55 km. In comparison to five existing Greenland geothermal heat flow models, our model has the lowest mean geothermal heat flow for Greenland onshore areas (44 mW m-2). Our model's most distinctive spatial feature is pronounced low geothermal heat flow (< 40 mW m-2) across the North Atlantic Craton of southern Greenland. Crucially, our model does not show an area of elevated heat flow that might be interpreted as remnant from the Icelandic Plume track. Finally, we discuss the substantial influence of paleoclimatic and other corrections on geothermal heat flow measurements in Greenland. The in-situ measurement database and gridded heat flow model, as well as other supporting materials, are freely available from the GEUS DataVerse (https://doi.org/10.22008/FK2/F9P03L; Colgan and Wansing, 2021). [ABSTRACT FROM AUTHOR]

In recent years, the aeromagnetic coverage over Antarctica has improved significantly. Nevertheless, aeromagnetic data suffer from a long-wavelength spectral gap compared to satellite data. That is due to how aeromagnetic data are acquired and processed. We examine, if by combination of satellite and aeromagnetic data, helps in geophysical inverse and forward modelling with a case example from the Gamburtsev Province, east Antarctica. In the modelling, we did not aim to produce a combined magnetic field model, but used the susceptibility distribution inverted from a satellite model as an input for modelling the aeromagnetic data. The results are compared with a second model, inverted without satellite data. The inclusion of the long-wavelength information from the satellite inversion does affect the final model, but does not significantly alter the location of sources in the upper crust. Hence, the combination is less important for geological interpretation, but significant for interpretation of the deepest magnetic sources. To determine the impact of the satellite models, we tested two different satellite models based on the CHAMP (MF7 @ 300 km) and Swarm (SIFM @ 400 km) satellite missions. In the last step, we validate the combined final models against the aeromagnetic and satellite data. [ABSTRACT FROM AUTHOR]