Simulating future contributions of the Greenland ice sheet to sea-level rise by using a coupled surface mass balance and ice sheet model

Abstract

The Greenland ice sheet is losing mass at an increasing rate and is expected to be an important contributor to global sea-level rise in the 21st century. Paleoclimatic records suggest that during warmer-than-present interglacials, the ice sheet has previously become unstable, potentially raising sea levels by up to seven meters. Studies indicate that the temperature threshold for an irreversible ice sheet collapse could be exceeded by the end of this century without adequate global reductions in greenhouse gas emissions. Constraining the temperature tipping point and providing realistic estimates of near-future sea-level rise is of great importance for mitigation and planning. However, uncertainty in future estimates of sea-level rise projections create the need for more research to aid in constraining and validating existing estimates. In this study, I have investigated the contribution of the Greenland ice sheet to global mean sea level rise by using the Bergen Snow Simulator (BESSI) coupled with a thermomechanical ice sheet model to simulate future ice sheet evolution under multiple emission scenarios for the 21st century and the current millennium. The atmospheric forcing input were simulations of multiple climate projection provided by 24 different Earth system models from the sixth phase of the Coupled Model Intercomparison Project (CMIP6). Furthermore, the ice sheet stability and potential sea-level contribution to an end-of-century forcing lasting from the year 2100 to 3000 was analysed. The model performance has been validated by simulation of the historical period 1990 to 2020, were produced realistic mass loss in agreement with observations. The future projection indicates, that for the SSP585 scenario, the Greenland ice sheet could contribute 82 mm with a midspread of 40 to 138mm of sea-level rise by the year 2100, and 2 m with a midspread of 0.9 – 3 m by the year 3000. The uncertainty in the estimates mainly arises from the differences between the ESMs. Additionally, the results indicate that the projected end-of-century temperature anomalies for SSP245 and SSP585 both trigger self-sustained melting, thereby destabilizing the ice sheet for the ensuing millennium.