Greenland Ice Sheet (GrIS) mass loss has accelerated in recent decades, primarily due to enhanced surface melt. Identifying the causal dependencies of surface melt remains challenging with conventional correlations. Using the (Formula presented.) causal discovery algorithm applied to CESM2 large-ensemble simulations and evaluated against two high-resolution regional climate models, we identify significant contemporaneous positive links from melt to net shortwave radiation (reflecting melt–albedo feedback) and from sensible and latent heat fluxes to melt. These results highlight shortwave radiation and turbulent heating as dominant drivers of GrIS summer melt anomalies over the ablation zone at monthly timescales. Compared with correlations, (Formula presented.) isolates fewer but more physically interpretable dependencies. By the end of the century (SSP3-7.0), these links persist but the turbulent heat-related ones become undirected, indicating reduced statistical identifiability and possible stronger instantaneous surface–atmosphere coupling in a warmer climate. ... Read more

The simulation of ice sheet-climate interactions, such as surface mass balance fluxes, is sensitive to model grid resolution. Here we simulate the multi-century evolution of the Greenland Ice Sheet (GrIS) and its interaction with the climate using the Community Earth System Model version 2.2 (CESM2.2) including an interactive GrIS component (the Community Ice Sheet Model v2.1 [CISM2.1]) under an idealized warming scenario (atmospheric (Formula presented.) increases by 1% (Formula presented.) until quadrupling the pre-industrial level and then is held fixed). A variable-resolution (VR) grid with 1/ (Formula presented.) regional refinement over the broader Arctic and (Formula presented.) resolution elsewhere is applied to the atmosphere and land components, and the results are compared with conventional (Formula presented.) lat-lon grid simulations to investigate the impact of grid refinement. Compared with the (Formula presented.) runs, the VR run features a slower rate of surface melt, especially over the western and northern GrIS, where the ice surface slopes gently toward the periphery. This difference pattern originates primarily from higher snow albedo and, thus, weaker albedo feedback in the VR run. The VR grid better captures the CISM ice sheet topography by reducing elevation discrepancies between CAM and CISM and is, therefore, less reliant on the downscaling algorithm, which is known to underestimate albedo gradients. The sea level rise contribution from the GrIS in the VR run is 53 mm by year 150 and 831 mm by year 350, approximately 40% and 20% less than that of the (Formula presented.) runs, respectively. ... Read more