Abstract
AbstractIn this study, we explore small-scale (~1 to 20 km) thermal-refractive effects on basal geothermal heat flux (BGHF) at subglacial boundaries resulting from lateral thermal conductivity contrasts associated with subglacial topography and geologic contacts. We construct a series of two-dimensional, conductive, steady-state models that exclude many of the complexities of ice sheets in order to demonstrate the effect of thermal refraction. We show that heat can preferentially flow into or around a subglacial valley depending on the thermal conductivity contrast with underlying bedrock, with anomalies of local BGHF at the ice–bedrock interface between 80 and 120% of regional BGHF and temperature anomalies on the order of ±15% for the typical range of bedrock conductivities. In the absence of bed topography, subglacial contacts can produce significant heat flux and temperature anomalies that are locally extensive (>10 km). Thermal refraction can result in either an increase or decrease in the likelihood of melting and ice-sheet stability depending on the conductivity contrast and bed topography. While our models exclude many of the physical complexities of ice behavior, they illustrate the need to include refractive effects created by realistic geology into future glacial models to improve the prediction of subglacial melting and ice viscosity.
Highlights
Geothermal heat flux at the base of ice sheets (BGHF) is a critical boundary constraint on icesheet models because it plays a key role in the basal temperature and thermal gradients within glaciers (Pittard and others, 2016)
We demonstrate the effect of heat refraction at the base of ice sheets in the presence of subglacial topography and above geological contacts
In many cases – where bedrock is more conductive than ice – heat flux and temperature will be reduced above topographic depressions, the opposite as predicted by the topographic effect
Summary
Geothermal heat flux at the base of ice sheets (BGHF) is a critical boundary constraint on icesheet models because it plays a key role in the basal temperature and thermal gradients within glaciers (Pittard and others, 2016). While more recent BGHF models derived from seismic tomography and Curie depth estimates are available (An and others, 2015; Martos and others, 2017; Lösing and others, 2020; Shen and others, 2020), these models are not of sufficient resolution to observe local thermal variations that may be significant to glacial processes (Liefferinge and Pattyn, 2013) These processes include the raising or lowering of the strain rate of ice (Goldsby and Kohlstedt, 2001), the formation of fast sliding ice streams (Engelhardt, 2004) and the formation of subglacial lakes in regions not defined by basic 1-D thermal gradients (Llubes and others, 2006). In a separate study by Young and others (2017), the authors assumed topography would increase the potential for subglacial lakes in regions of deeply incised topography
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call