Heat flow variations in the Antarctic Continent

The present work provides a reappraisal of terrestrial heat flow variations in the Antarctic continent, based on recent advances in data analysis and regional assessments. The data considered include those reported at the website of IHFC and 78 additional sites where measurements have been made using a variety of techniques. These include values based on the Method of Magmatic Heat Budget (MHB) for 41 localities in areas of recent volcanic activity and estimates that rely on basal temperatures of glaciers in 372 localities that are known to host subglacial lakes. The total number of data assembled is 491, which has been useful in deriving a 10°x10° grid system of homogenized heat flow values and in deriving a new heat flow map of the Antarctic continent. The results reveal that the Antarctic Peninsula and western segment of the Antarctic continent has distinctly high heat flow relative to the eastern regions. The general pattern of differences in heat flow between eastern and western of Antarctic continent is in striking agreement with results based on seismic velocities.

Mantle-induced temperature anomalies do not reach the inner core boundary

SUMMARY Temperature anomalies in Earth’s liquid core reflect the vigour of convection and the nature and extent of thermal core–mantle coupling. Numerical simulations suggest that longitudinal temperature anomalies forced by lateral heat flow variations at the core–mantle boundary (CMB) can greatly exceed the anomalies that arise in homogeneous convection (i.e. with no boundary forcing) and may even penetrate all the way to the inner core boundary. However, it is not clear whether these simulations access the relevant regime for convection in Earth’s core, which is characterized by rapid rotation (low Ekman number E) and strong driving (high Rayleigh number Ra). We access this regime using numerical simulations of non-magnetic rotating convection with imposed heat flow variations at the outer boundary (OB) and investigate the amplitude and spatial pattern of thermal anomalies, focusing on the inner and outer boundaries. The 108 simulations cover the parameter range 10−4 ≤ E ≤ 10−6 and Ra = 1−800 times the critical value. At each Ra and E we consider two heat flow patterns—one derived from seismic tomography and the hemispheric $Y_1^1$ spherical harmonic pattern—with amplitudes measured by the parameter q⋆ = 2.3, 5 as well as the case of homogeneous convection. At the OB the forcing produces strong longitudinal temperature variations that peak in the equatorial region. Scaling relations suggest that the longitudinal variations are weakly dependent on E and Ra and are much stronger than in homogeneous convection, reaching O(1) K at core conditions if q⋆ ≈ 35. At the inner boundary, latitudinal and longitudinal temperature variations depend weakly on Ra and q⋆ and decrease strongly with E, becoming practically indistinguishable between homogeneous and heterogeneous cases at E = 10−6. Interpreted at core conditions our results suggest that heat flow variations on the CMB are unlikely to explain the large-scale variations observed by seismology at the top of the inner core.

Regional estimation of Curie-point depths and succeeding geothermal parameters from recently acquired high-resolution aeromagnetic data of the entire Bida Basin, north-central Nigeria

<p><strong>Abstract.</strong> A regional estimation of Curie-point depths (CPDs) and succeeding geothermal gradients and subsurface crustal heat flow has been carried out from the spectral centroid analysis of the recently acquired high-resolution aeromagnetic (HRAM) data of the entire Bida Basin in north-central Nigeria. The HRAM data were divided into 28 overlapping blocks, and each block was analysed to obtain depths to the top, centroid, and bottom of the magnetic sources. The depth values were then used to assess the CPD, geothermal gradient, and subsurface crustal heat flow in the basin. The result shows that the CPD varies between 15.57 and 29.62<span class="thinspace"></span>km with an average of 21.65<span class="thinspace"></span>km, the geothermal gradient varies between 19.58 and 37.25<span class="thinspace"></span>°C<span class="thinspace"></span>km⁻¹ with an average of 27.25<span class="thinspace"></span>°C<span class="thinspace"></span>km⁻¹, and the crustal heat flow varies between 48.41 and 93.12<span class="thinspace"></span>mW<span class="thinspace"></span>m⁻² with an average of 68.80<span class="thinspace"></span>mW<span class="thinspace"></span>m⁻². Geodynamic processes are mainly controlled by the thermal structure of the Earth's crust; therefore this study is important for appraisal of the geo-processes, rheology, and understanding of the heat flow variations in the Bida Basin, north-central Nigeria.</p>