Abstract
Abstract. Polar amplification will result in amplified temperature changes in the Arctic with respect to the rest of the globe, making the Greenland ice sheet particularly vulnerable to global warming. While the ice sheet has been showing an increased mass loss in the past decades, its contribution to global sea level rise in the future is of primary importance since it is at present the largest single-source contribution after the thermosteric contribution. The question of the fate of the Greenland and Antarctic ice sheets for the next century has recently gathered various ice sheet models in a common framework within the Ice Sheet Model Intercomparison Project for the Coupled Model Intercomparison Project – phase 6 (ISMIP6). While in a companion paper we present the GRISLI-LSCE (Grenoble Ice Sheet and Land Ice model of the Laboratoire des Sciences du Climat et de l'Environnement) contribution to ISMIP6-Antarctica, we present here the GRISLI-LSCE contribution to ISMIP6-Greenland. We show an important spread in the simulated Greenland ice loss in the future depending on the climate forcing used. The contribution of the ice sheet to global sea level rise in 2100 can thus be from as low as 20 mm sea level equivalent (SLE) to as high as 160 mm SLE. Amongst the models tested in ISMIP6, the Coupled Model Intercomparison Project – phase 6 (CMIP6) models produce larger ice sheet retreat than their CMIP5 counterparts. Low-emission scenarios in the future drastically reduce the ice mass loss. The oceanic forcing contributes to about 10 mm SLE in 2100 in our simulations. In addition, the dynamical contribution to ice thickness change is small compared to the impact of surface mass balance. This suggests that mass loss is mostly driven by atmospheric warming and associated ablation at the ice sheet margin. With additional sensitivity experiments we also show that the spread in mass loss is only weakly affected by the choice of the ice sheet model mechanical parameters.
Highlights
The relative contribution of land ice to global mean sea level rise has considerably increased in the recent decades and is larger than the thermosteric effect (Nerem et al, 2018)
Forcing used to drive the ice sheet model, we have shown that the Greenland ice sheet systematically loses ice in the future
Under a businessas-usual scenario for the greenhouse gas emission (RCP8.5 or SSP585), the mass loss translates into a Greenland ice sheet contribution to global sea level rise that ranges from 35 to 160 mm sea level equivalent (SLE)
Summary
The relative contribution of land ice to global mean sea level rise has considerably increased in the recent decades and is larger than the thermosteric effect (Nerem et al, 2018). The Greenland and Antarctic ice sheets have potential to substantially raise the global mean sea level, with a weakly constrained trajectory (Oppenheimer et al, 2019). While observational datasets show a dramatic increase in mass loss over the last decades for both ice sheets (Mouginot et al, 2019; Rignot et al, 2019), there is an urgent need for robust assessment of future sea level rise by projections obtained with numerical models. These projections involve comprehensive ice sheet models that compute the ice thickness change that results from evolving forcings, such as climate change.
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