Elevated geothermal surface heat flow in the Amundsen Sea Embayment, West Antarctica

Abstract

Keywords: skin depth for geothermal gradients spatial variation of geothermal heat flow on small scales in situ temperature measurements geotherm transitionThe thermal state of polar continental crust plays a crucial role for understanding the stability and thickness of large ice sheets, the visco-elastic response of the solid Earth due to unloading when large ice caps melt and, in turn, the accuracy of future sea-level rise prediction. Various studies demonstrate the need for precise measurements and estimation of geothermal heat flow (GHF) in Antarctica for better constrained boundary conditions to enhance the ice sheet model performance. This study provides ground-truth for regional indirect GHF estimates in the Amundsen Sea Embayment, which is part of the West Antarctic Rift System, by presenting in situ temperature measurements in continental shelf sediments. Our results show regionally elevated and heterogeneous GHF (mean of 65 mW m −2 ) in the Amundsen Sea Embayment. Considering thermal blanketing effects, induced by inflow of warmer water and sedimentary processes, the estimated GHF ranges between 65 mW m −2 and 95 mW m −2 .

Geothermal heat flow in Antarctica: current and future directions

“…Whilst large (>10 °C) seasonal temperature variations are dampened by ~90% at water depths of 3-5 m (Müller et al, 2016), long-term variations (e.g. climate-controlled variations in Circumpolar Deep Water over the last ~12 kyr; Hillenbrand et al, 2017) are likely recorded in the upper 3 m at 400 m water depth, 2 m at 700 m depth, and even the upper ~1 m at 1000 m depth (Dziadek et al, 2019).…”

“…Similarly to borehole temperature measurements, a time delay must be considered between penetration of the sediments and temperature measurement. A ten minute delay between sediment penetration and measurement is sufficient to allow decay of frictional heating, as the temperature decay takes ~100 s (Dziadek et al, 2019;Pfender and Villinger, 2002).…”

“…However, the data distribution is sparse and heterogeneous, and whilst some regions are well sampled (e.g. the Amundsen Sea embayment; Dziadek et al, 2019Dziadek et al, , 2017, other regions (e.g. the Weddell Sea) remain poorly constrained (Fig.…”

“…temperature gradient recorded by the probe is representative of the deeper GHF, or will have been perturbed by temperature variation in the overlying ice sheet or water column (e.g. Dziadek et al, 2019). Consequently, the water depth, the temperature profile of the water column, and possible sources of long-term temperature variation (e.g.…”

The uppermost mantle seismic velocity structure of West Antarctica from Rayleigh wave tomography: Insights into tectonic structure and geothermal heat flow

“…ences from satellite magnetic data (∼55-65 mW/m 2 ; FoxMaule et al, 2005), seismic data (∼70 mW/m 2 ;An et al, 2015a), airborne magnetic data (∼60-75 mW/m 2 ;Martos et al, 2017), and in situ measurements in continental shelf sediments in the Amundsen Sea Embayment (mean ∼65 mW/m 2 ;Dziadek et al, 2019). Our preferred ∼60 mW/m 2 heat flow at PIG3 again contrasts with the ∼110 mW/m 2 modelled byShapiro & Ritzwoller (2004); however, their modelled standard deviations are of comparable magnitude to their inferred heat flows.Our preferred heat flow of ∼50 mW/m 2 at node 1624 in the Ellsworth Mountains is lower than estimates based on satellite magnetic data(∼70 mW/m 2 ; Fox Maule et al, 2005) and airborne magnetic data (∼65-70 mW/m 2 ; Martos et al, 2017), but reasonably consistent with recent seismic-based inferences (∼55 mW/m 2 ; An et al, 2015a).…”