Exploring the Greenland Ice Sheet's response to future atmospheric warming-threshold scenarios over 200 years

Abstract. The Greenland Ice Sheet (GrIS) plays a crucial role in sea level rise (SLR). We investigate its response to warming thresholds over two centuries using a coupled regional-atmospheric ice sheet model (MAR-PISM, respectively run at 25 km and 4.5 km resolutions). We explore responses under global atmospheric warmings from +0.6 °C to +5.8 °C since pre-industrial temperatures and assess GrIS recovery if the climate reverts to present conditions, while prescribing unchanged ocean conditions. Our study then only evaluates the effect of atmospheric changes on the Greenland ice sheet. Moderate atmospheric warmings (+0.6 °C to +1.4 °C) yield steady and similar SLR contributions (from +8.35 to +9.55 cm in 2200), close to levels already committed under the present climate. Global temperature increases beyond +1.4°C mark a critical threshold, triggering non-linear mass loss due to feedback mechanisms like the melt-albedo effect and firn saturation. The SLR increase between the +1.4 °C and +2.3 °C experiments is larger (+7.56 cm), highlighting an accelerating mass loss. This trend is further reinforced by the even greater increase of 15.51 cm between +4.4 °C and +5.2 °C, underscoring the amplified impact of higher warming levels. Reversing the climate after surpassing +2.3 °C demonstrates the potential for GrIS stabilization, though at a new reduced state of equilibrium (around 4 % smaller). These findings underscore the impact of thresholds and time spent above them, highlighting the importance of limiting anthropogenic warming to maintain GrIS stability and mitigate long-term SLR.