Abstract
AbstractGeothermal heat flux (GHF) is an important control on the dynamics of Antarctica's ice sheet because it controls basal melt and internal deformation. However, it is hard to estimate because of a lack of in-situ measurements. Estimating GHF from ice-borehole temperature profiles is possible by combining a heat-transfer equation and the physical properties of the ice sheet in a numerical model. In this study, we truncate ice-borehole temperature profiles to determine the minimum ratio of temperature profile depth to ice-sheet thickness required to produce acceptable GHF estimations. For Law Dome, a temperature profile that is within 60% of the local ice thickness is sufficient for an estimation that is within approximately one median absolute deviation of the whole-profile GHF estimation. This result is compared with the temperature profiles at Dome Fuji and the West Antarctic Ice Sheet divide which require a temperature profile that is 80% and more than 91% of the ice thickness, respectively, for comparable accuracy. In deriving GHF median estimations from truncated temperature profiles, it is possible to discriminate between available GHF models. This is valuable for assessing and constraining future GHF models.
Highlights
The potential of the Antarctic Ice Sheet (AIS) to raise global sea levels by up to 58 m (Fretwell and others, 2013) means that understanding the impacts of a warming climate on the southern polar region is one of the grand scientific challenges of our time (Bell, 2008)
We explore the regional applicability of this analysis with comparisons to the Dome Fuji and West Antarctic Ice Sheet (WAIS) divide ice core sites (WDC) (Fig. 1)
Our model is able to assess the variation in Geothermal heat flux (GHF) estimations from ice-borehole temperature profiles truncated at different depths
Summary
The potential of the Antarctic Ice Sheet (AIS) to raise global sea levels by up to 58 m (Fretwell and others, 2013) means that understanding the impacts of a warming climate on the southern polar region is one of the grand scientific challenges of our time (Bell, 2008). The vulnerability of the AIS underscores the need for more accurate ice-sheet models, these are crucial for understanding ice dynamics and future ice flow variations. Geothermal heat flux (GHF) is an important thermal boundary condition in these models because it affects the temperature at the base of the ice sheet and is the dominant control on basal temperatures in slow-flowing areas (Larour and others, 2012; Pittard and others, 2016). Ice flow is sensitive to the local spatial variation of underlying GHF, especially near ice divides and at the edge of ice streams (Bell and others, 2007; Pittard and others, 2016). Local GHF is a first-order consideration in site selection for climate records, especially in the search for ‘old’ (million-year) ice core sites. Locations where ice is at pressure melting point can lead to melt-driven erosion of the glacial stratigraphy, reducing the temporal range of the climate record (Fischer and others, 2013; Liefferinge and Pattyn, 2013; Parrenin and others, 2017; Karlsson and others, 2018)
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