Abstract
AbstractThe spatial distribution of geothermal heat flux (GHF) under ice sheets is largely unknown. Nonetheless, it is an important boundary condition in ice-sheet models, and suggested to control part of the complex surface velocity patterns observed in some regions. Here we investigate the effect of including subglacial hydrology when modelling ice streams with elevated GHF. We use an idealised ice stream geometry and a thermomechanical ice flow model coupled to subglacial hydrology in the Ice Sheet System Model (ISSM). Our results show that the dynamic response of the ice stream to elevated GHF is greatly enhanced when including the interactive subglacial hydrology. On the other hand, the impact of GHF on ice temperature is reduced when subglacial hydrology is included. In conclusion, the sensitivity of ice stream dynamics to GHF is likely to be underestimated in studies neglecting subglacial hydrology.
Highlights
Geothermal heat flux (GHF) impacts the basal thermal regime of ice sheets (Rogozhina and others, 2012; Seroussi and others, 2017)
Note that we only show the upper 350 km of the domain, as we focus on how the GHF anomaly may influence the onset of the ice stream
We have investigated the impact of using a subglacial hydrology model on the dynamic and thermal response of an ice stream to elevated geothermal heat flux
Summary
Geothermal heat flux (GHF) impacts the basal thermal regime of ice sheets (Rogozhina and others, 2012; Seroussi and others, 2017). GHF has two main effects on ice dynamics: it affects internal flow through its impact on ice temperature altering the ice rheology (Glen, 1955) and it can increase the sliding rates by providing basal meltwater in regions otherwise not subject to surface water input. Basal meltwater lubricates the bed and facilitates sliding. For this reason, high GHF anomalies are thought to initiate and sustain some ice streams (Blankenship and others, 1993; Bourgeois and others, 2000; Fahnestock and others, 2001; Näslund and others, 2005; Bell, 2008; Winsborrow and others, 2010; Rogozhina and others, 2016). GHF is one of the least known boundary conditions in ice-sheet models, and uncertainties in GHF may explain why surface velocities in some regions are not well reproduced in models without inverting for basal conditions
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