Greenland ice sheet evolution and stability

The Greenland ice sheet is one of the largest contributors to sea-level rise today and is expected to continue losing mass in the future under increasing Arctic warming. Sea-level rise is threatening people’s habitat, livelihoods, and infrastructure. Therefore, reducing uncertainties in projections of future sea-level contribution from the Greenland ice sheet is of the highest importance. The research project "Greenland ice sheet evolution and stability" had two main objectives that address the response of the ice sheet to climate change in the short-term and the long-term, respectively. The first objective was to determine upper bounds for rates of sea-level contribution from the Greenland ice sheet until 2100. We have reached that objective by providing ice sheet and sea-level projections for a large range of climate warming trajectories taking into account various sources of uncertainty. The results serve as input for planners working on protection for cities and infrastructure in coastal areas worldwide. The second objective was to constrain climate change trajectories that lead to a stabilisation of the Greenland ice sheet until 2300 or later. To address this objective we have used a novel modelling technique to investigate ice sheet evolution and stabilisation under various warming levels. The results show that the ice sheet cannot be stabilised without active climate protection measures. With this research we have contributed to the evaluation of global mitigation targets to avoid a substantial loss of the Greenland ice sheet.

The main scientific outcomes of the project are an improved understanding of the potential sea-level contribution from the Greenland ice sheet under various warming scenarios and the warming levels that could lead to a long-term stabilisation of the ice sheet. This has strong bearing on planning of coastal management and adaptation to future sea-level rise and on the evaluation of global mitigation targets to avoid a substantial loss of the Greenland ice sheet. The results of the project are directly informing future work in the international Ice Sheet Model Intercomparison Project (ISMIP7) that is expected to deliver sea-level projections in time for the next IPCC assessment report (AR7). The project has helped to position our research team among the internationally leading groups working on ice sheet sea-level projections and coupled ice sheet-climate modelling. The international contacts established and maintained during the project have linked us with stakeholders and allowed us to provide our results in a format most relevant for planners. The expected societal impacts of the project are that sea-level practitioners have a more complete account of expected maximum rates of sea-level change from the Greenland ice sheet to work with and that remaining uncertainties are better characterised. In addition, our work on ice sheet stabilisation may provide guidance for policy makers when considering targets for climate mitigation.

The Greenland ice sheet is one of the largest contributors to global mean sea-level rise today and is expected to continue losing mass in the future under increasing Arctic warming. Sea-level rise is threatening people’s habitat, livelihoods, and infrastructure. Therefore, reducing uncertainties in projections of future sea-level contribution from the Greenland ice sheet is of the highest importance for people living close to the coast and for planners working on protection plans for cities and infrastructure in coastal areas worldwide. In addition, it has been argued that warming beyond a certain threshold already during our own lifetime could bring the ice sheet over a tipping point and into a sustained and irreversible retreat, leading to meters of sea-level rise on a thousand-year timescale. The research project GREASE will provide a fundamental breakthrough in our understanding of the future stability of the Greenland ice sheet and its associated sea-level contribution using novel modelling techniques (standalone and coupled ice sheet-Earth System modelling). In close exchange with users, GREASE will provide actionable science to coastal planners and policy makers.