The Greenland ice sheet (GrIS) contains enough water to raise global sea level by about 7 m. Recent research shows that meltwater that has formed at the ice sheet surface drains to the bed of the glacier, accelerating the ice flow. As a result, the glacier thins, the surface lowers, melting increases and the cycle starts anew. This positive feedback between surface climate and ice dynamics is part of the mounting evidence that large ice volumes such as the GrIS could react much faster to a change in climate than has been assumed thus far. In spite of the potential threat this poses for low-lying countries such as the Netherlands, it is still unknown whether the GrIS is growing or shrinking under the present climate conditions and how it has contributed to sea level change in the past and will contribute to sea level change in the future.
A crucial boundary condition for the accurate modelling of past, present and future volume changes of the GrIS is the surface mass balance, comprising the sum of all mass fluxes towards (solid precipitation) and away (melt, sublimation, erosion) from the ice sheet surface. Because reliable GrIS surface mass balance fields are not available, we do not know the volume of the GrIS and its contribution to sea level changes during the previous interglacial (the Eemian, 125,000 years ago) or during the last glacial maximum (LGM, some 21,000 years ago), nor can we predict with any certainty how the GrIS will behave in a (future) enhanced greenhouse climate.
In this project, the surface mass balance of the GrIS will be modelled for these key periods in the past and future. By using a regional atmospheric climate model (RACMO2), driven at the boundaries by state-of-the-art atmospheric general circulation models, this can be done at unprecedented high resolution (18 km) to match the typical resolution of ice dynamical models. Another big advantage of using a meteorological model is the availability of spatially and temporally realistic melt fluxes to study the interaction with ice dynamics. With results from this research we will be able to hindcast and predict the changes in the volume of the GrIS with much improved accuracy and with that its contribution to past and future changes in global sea level.