The Greenland ice sheet holds enough water to raise the global sea-level with ~ 7 m. Over the last few decades, observations manifest a substantial increase of the mass loss of this ice sheet. Both enhanced melting and increase of the dynamical discharge, associated with calving at the outlet-glacier fronts, are contributing to the mass imbalance. Using dynamical and thermodynamical ice-sheet models, and taking into account speed up of outlet glaciers, we estimate Greenland’s contribution to the 21st century global sea-level rise and the uncertainty of this estimate. Boundary fields of temperature and precipitation extracted from coupled climate-model projections used for the IPCC Forth Assessment Report, are applied to the ice-sheet models. We implement a simple parameterization for increased flow of outlet glaciers, which decreases the bias of the modeled present-day surface height. It also allows for taking into account the observed recent increase in dynamical discharge, and it can therefore be used for future projections associated with outlet-glacier speed up. Greenland contributes 1-14 cm to global sea-level rise by the end of the 21st century. This range includes the uncertainties in climate models projections, the uncertainty associated with scenarios of greenhouse-gas emissions, as well as the uncertainties in future outlet-glacier discharge. In addition, the range takes into account the uncertainty of the ice-sheet model and its boundary fields.
- antarctic ice sheets