Cryo-hydrologic Warming Explains Increased Ice Velocities on a Glacier in West 
Greenland

The area of west Greenland  experiencing surface melt is increasing at a rate of 
~3.9% per year, in response to a > 200m increase in equilibrium line altitude 
(ELA) over the past decade. A significant fraction of this meltwater enters the ice 
sheet through conduits and crevasses.  Recent observations suggest that 
meltwater is retained in the englacial and subglacial cryo-hydrologic systems 
(CHS) through multiple years in this region.  We demonstrate through latent heat 
transfer from this retained meltwater has the potential to warm ice significantly 
and relatively rapidly (decadal time scales), a process, which we have termed 
"cryo-hydrologic warming" (CHW). We further demonstrate that the ice 
progressively develops heterogeneous temperature distributions, with 
permanent near-temperate conditions in the vicinity of the cryo-hydrologic 
systems.  Warmer ice temperature will lead to reduced ice viscosity and lead to 
higher ice velocity through a thermomechanical feedback. We demonstrate that 
ice surface velocities measured on Sermeq Avannarleq in west Greenland, in 
2005/065 cannot be reproduced unless the influence of CHW is invoked; 
conventional thermo-mechanical models predict surface velocities that are up to 
70 m/a less than observed velocities.  Although contemporary temperature data 
are not available, the sole ice temperature measurements in this region (from 
1990) are also matched only when the influence of CHW is incorporated. 
Conventional thermo-mechanical models predict much colder temperatures and 
temperature profiles that are not even qualitatively similar to the observed 
profiles.  Thus, our results strongly support the notion that CHW is a significant 
factor contributing to the recent acceleration of ice flow in west Greenland.  

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