Subglacial Discharge of the Greenland Ice Sheet from Basal Melt

Séminaire de N. Karlsson le Jeudi 28 Janvier à 11h en visio

Title : Subglacial Discharge of the Greenland Ice Sheet from Basal Melt

Seminar by Nanna Karlsson, Geological Survey of Denmark and Greenland, Copenhagen, Denmark

abtsract :
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 not explicitly included in either of these total mass balance estimates. 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.