EGU21-7304
https://doi.org/10.5194/egusphere-egu21-7304
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Subglacial Discharge of the Greenland Ice Sheet from Basal Melt

Nanna Bjørnholt Karlsson1, Anne M Solgaard1, Kenneth D Mankoff1, Fabien Gillet-Chaulet2, Joseph A. MacGregor3, Douglas I. Benn4, Ian Hewitt5, and Robert S. Fausto1
Nanna Bjørnholt Karlsson et al.
  • 1Geological Survey of Denmark and Greenland, Glaciology and Climate, Copenhagen, Denmark (nbk@geus.dk)
  • 2University of Grenoble Alpes, CNRS, IGE, Grenoble, France
  • 3Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA
  • 4School of Geography & Sustainable Development, University of St. Andrews, St. Andrews, UK
  • 5Oxford Centre for Industrial and Applied Mathematics, University of Oxford, Oxford, UK

The total mass balance of ice sheets is determined using estimates of ice volume change from satellite altimetry, measurements of gravity changes, or by differencing solid ice discharge and surface mass balance. The basal melt is only implicitly included in the first two and entirely neglected by the last method. Here, we show that the basal mass loss of the Greenland Ice Sheet is a non-negligible component of the total mass budget. We estimate that the basal melt is 21.4 +4.4/-4.0 Gt per year corresponding to 8% of the ice sheet’s total mass balance. The basal melt is composed of three separate terms; melt caused by frictional heat, geothermal heat and heat from surface meltwater, respectively, and the basal friction term is responsible for half of the basal melt.

Importantly, the geothermal and friction heat are active year round. This implies that a quantifiable volume of freshwater is discharged into the Greenlandic fjords during the winter where the ice-fjord interactions often are assumed dormant. Here, we present basal melt volumes from different outlet glaciers that discharge into Greenlandic fjords. We compare the basal melt to the freshwater volumes generated by surface meltwater, and identify locations where basal melt volumes are comparable to surface meltwater during the winter.

How to cite: Karlsson, N. B., Solgaard, A. M., Mankoff, K. D., Gillet-Chaulet, F., MacGregor, J. A., Benn, D. I., Hewitt, I., and Fausto, R. S.: Subglacial Discharge of the Greenland Ice Sheet from Basal Melt, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-7304, https://doi.org/10.5194/egusphere-egu21-7304, 2021.