Rapid basal melting of the Greenland Ice Sheet from surface meltwater drainage

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Christoffersen, Poul  ORCID logo  https://orcid.org/0000-0003-2643-8724
Tulaczyk, Slawek 
Mankoff, Kenneth 

Subglacial hydrologic systems regulate ice sheet flow, causing acceleration or deceleration depending on hydraulic efficiency and the rate at which surface meltwater is delivered to the bed. Because these systems are rarely observed, ice sheet basal drainage represents a poorly integrated and uncertain component of models used to predict sea-level changes. Here, we report radar-derived basal melt rates and unexpectedly warm subglacial conditions beneath a large Greenlandic outlet glacier. The basal melt rates averaged 14 mm d−1 over 4 months, peaking at 57 mm d−1 when basal wa-ter temperature reached +0.88 C in a nearby borehole. We attribute both observations to the conversion of potential energy of surface water as heat in the basal drainage system, which peaked during a period of rainfall and intense surface melting. Our findings reveal limitations in the theory of channel formation and we show that viscous dissipation far surpasses other basal heat sources, even in a distributed, high-pressure system.

Greenland, climate change, glaciology, ice sheets, radio echo sounding
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Proceedings of the National Academy of Sciences of USA
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National Academy of Sciences
Natural Environment Research Council (NE/K005871/1)
European Commission Horizon 2020 (H2020) ERC (3276207)
Natural Environment Research Council (NE/S006788/1)
EU Horizon 2020