Basin-scale partitioning of Greenland ice sheet mass balance components (2007-2011)

- We use airborne surveys of the GrIS to estimate ice flux from the interior 2007-2011.
- We use a regional climate model to estimate surface mass balance near the coast.
- 2007-2011 mean iceberg discharge into the ocean is 515 Gt/a.
- Ice sheet mass balance for 2007-2011 is −262 Gt/a.
- Surface melt dominates solid ice discharge in the total mass balance.

The current deficit in Greenland ice sheet mass balance is due to both a decrease in surface mass balance (SMB) input and an increase in ice discharge (D) output. While SMB processes are beginning to be well captured by observationally-constrained climate modeling, insight into D is relatively limited. We use InSAR-derived velocities, in combination with ice thickness observations, to quantify the mass flux (F) across a flux perimeter around the ice sheet at ∼1700 m elevation. To quantify D, we correct F for SMB, as well as changes in volume due to ice dynamics, in the area downstream of the gate. Using a 1961-1990 reference climatology SMB field from the MAR regional climate model, we quantify ice sheet mass balance within eighteen basins. We find a 2007-2011 mean D of 515±57 Gtyr−1. We find a 2007-2011 mean total mass balance of −262±21 Gtyr−1, which is equal to a 0.73 mm yr−1 global sea level rise contribution. This mass loss is dominated by SMB, which accounts for 61% of mass loss in the basins where partitioning is possible.