Limited global effect of climate-Greenland ice sheet coupling in NorESM2 under a high-emission scenario

Abstract. The Greenland ice sheet is melting at an accelerating rate due to the warming climate. In order to understand the potentially important ice-climate feedback processes, evolving ice sheets need to be included in global climate models. Here, we present results from the first bi-directional coupling of the Earth System model NorESM2 with the ice sheet model CISM2 for the Greenland ice sheet under an extended high emission SSP5-8.5 forcing from 1850 to 2300. In our simulation, the ice-mass loss between 1850 and 2300 is equivalent to 1.4 m of sea-level rise. Comparing simulation results to an otherwise identical simulation with a fixed Greenland ice sheet, we see the same global trends in air, ocean and sea-ice changes. The main signals are a 10 °C global air temperature increase from 2000 to 2300, a reduced maximum AMOC at 26.5° N from average 23 to 9 Sv and an all-year free Arctic by 2200. Similar to other coupled CMIP models, the warming trend dominates the changes of the climate components. At the regional scale, elevation changes become an important part of the Greenland surface mass balance, accounting for 20 % of the SMB change by 2200 and for 49 % in 2300. By the year 2300, the ablation area covers 93 % of the ice area. With a low climate sensitivity and relatively weak polar amplification in NorESM2, these results are on the lower end of the spectrum of expected ice mass-loss under CMIP6 model forcing.