The past, present, and future viscous heat dissipation available for Greenland subglacial conduit formation
Other literature type
Mankoff, Kenneth D.
Tulaczyk, Slawek M.
(issn: 1994-0424, eissn: 1994-0424)
Basal hydrology of the Greenland Ice Sheet (GIS) influences its dynamics and
mass balance through basal lubrication and ice–bed decoupling or efficient
water removal and ice–bed coupling. Variations in subglacial water pressure
through the seasonal evolution of the subglacial hydrological system help
control ice velocity. Near the ice sheet margin, large basal conduits are
melted by the viscous heat dissipation (VHD) from surface runoff routed to
the bed. These conduits may lead to efficient drainage systems that lower
subglacial water pressure, increase basal effective stress, and reduce ice
velocity. In this study we quantify the energy available for VHD
historically at present and under future climate scenarios. At present,
345 km<sup>3</sup> of annual runoff delivers 66 GW to the base of the ice sheet
per year. These values are already ∼ 50 % more than the historical
1960–1999 value of 46 GW. By 2100 under IPCC AR5 RCP8.5 (RCP4.5) scenarios, 1278 (524) km<sup>3</sup> of runoff may deliver 310 (110) GW to the ice sheet base. Hence, the ice sheet may experience a 5-to-7-fold increase in VHD in the near future which will enhance opening of subglacial conduits near the margin and will warm basal ice in the interior. The other significant basal
heat source is geothermal heat flux (GHF), which has an estimated value of 36
GW within the present-day VHD area. With increasing surface meltwater
penetration to the bed the basal heat budget in the active basal hydrology
zone of the GIS will be increasingly dominated by VHD and relatively less
sensitive to GHF, which may result in spatial changes in the ice flow field
and in its seasonal variability.